Quick Overview of SafeHome The SafeHome company has developed an innovative HW box that implements wireless Internet (802.11) connectivity in a very small form factor (the size of a matchbook). The idea is to use this technology to develop and market a comprehensive home automation product line. This would provide security functions, control over telephone answering machines, lights, heating, air conditioning, and home entertainment devices. The first generation of the system will only focus on home security and surveillance since that is a market the public readily understands. CS550 Intro. to SE Spring 2007 1 How a Project Starts (pg 48) The scene: Meeting room at CPI Corporation, a (fictional) company that makes consumer products for home and commercial use. The players: Mal Golden, senior manager, product development; Lisa Perez, marketing manager; Lee Warren, engineering manager; Joe Camalleri, executive VP, business development.
The conversation: Joe: Okay, Lee, what's this I hear about your folks developing a what? A generic universal wireless box? Lee: It's pretty cool, about the size CS550 Intro. to SE Spring 2007 of a small matchbook. We can attach it to sensors of all kinds, a digital camera, just about anything. Using the 802.11 b wireless protocol. It allows us to access the device's output without wires. We think it'll lead to a whole new generation of products. Joe: You agree, Mal? Mal: I do. In fact, with sales as flat as they've been this year, we need something new. Lisa and I have been doing a little market research, and we think we've got a line of products that could be big. 2 Joe: How big... , bottom-line Mal: (avoiding a direct commitment): Tell him about our idea, Lisa. Lisa: It's a whole new generation of what we call "home management products." We call 'em SafeHome. They use the new wireless interface, provide homeowners or small business people with a system that's controlled by their PC--home security, home surveillance, appliance and device control. You know, turn down the home air conditioner
while you're driving home, that to SE sortCS550 of Intro. thing. Spring 2007 Lee: (jumping in) Engineering's done a technical feasibility study of this idea, Joe. It's doable at low manufacturing cost. Most hardware is off the shelf. Software is an issue, but it's nothing that we can't do. Joe: Interesting. Now, I asked about the bottom line. Mal: PCs have penetrated 60 percent of all households in the USA. If we could price this thing right, it could be a killer-App. Nobody else has our wireless box--it's proprietary. We'll have a two-year jump on the competition. Revenue? Maybe as much as $30-40 million in the second year. 3 Joe (smiling): Let's take this to the Selecting a Process Model, Part 1(pg 85-86) The scene: The players: Meeting room for the software engineering group at CPI Corporation, a (fictional) company that makes consumer products for home and
commercial use. Lee Warren, engineering manager; Doug Miller, software engineering manager; Jamie Lazar, software team member; Vinod Raman, software team member; Ed Robbins, software team member. The conversation: Lee: So let's recapitulate. I've spent some time discussing the SafeHome product line as we CS550 Intro. to SE Spring 2007 see it at the moment. No doubt, we've got a lot of work to do to simply define the thing, but I'd like you guys to begin thinking about how you're going to approach the software part of this project. Doug: Seems like we've been pretty disorganized in our approach to software in the past. Ed: I don't know, Doug. We always got product out the door. Doug: True, but not without a lot of grief, and this project looks like it's bigger and 4 complex than anything we've done in the past. Jamie: Doesn't look that hard, but I agree ... our ad hoc approach to past projects won't work here, particularly if we have a very tight timeline. Doug (smiling): I want to be a bit more professional in our approach. I went to a short course last week and learned a lot about software engineering ... good stuff. We need a process here. Jamie (with a frown): My job
isIntro. to tobuild computer CS550 SE Spring 2007 programs, not push paper around. Doug: Give it a chance before you go negative on me. Here's what I mean. [Doug proceeds to describe the process framework described in Chapter 2 and the prescriptive process models presented to this point. Doug: So anyway, it seems to me that a linear model is not for us ... assumes we have all requirements up front and knowing this place, that's not likely. Vinod: Yeah, and that RAD model sounds way too IT- 5 oriented ... probably good for building an inventory control system or something, but it's just not right for SafeHome. Doug: I agree. Ed: That prototyping approach seems OK. A lot like what we do here anyway. Vinod: That's a problem. I'm worried that it doesn't provide us with enough structure. Doug: Not to worry. We've got plenty of other options, and I want you guys to pick what's best for the team and CS550 Intro.the to SE project. best for Spring 2007 6
Selecting a Process Model, Part 2(pg 90-91) The scene: The players: Meeting room for the software engineering group at CPI Corporation, a company that makes consumer products for home and commercial use. Lee Warren, engineering manager; Doug Miller, software engineering manager; Ed and Vinod, members of the software engineering team. The conversation: (Doug describes evolutionary process options.) Ed: Now I see something I like. An incremental approach makes CS550 Intro. to SE Spring 2007 sense and I really like the flow of that spiral model thing. That's keepin' it real. Vinod: I agree. We deliver an increment, learn from customer feedback, replan, and then
deliver another increment. It also fits into the nature of the product. We can have something on the market fast and then add functionality with each version, er, increment. Lee: Wait a minute, did you say that we regenerate the plan with each tour around the spiral, Doug? That's not so great, we 7 need one plan, one schedule, and we've got to stick to it. Doug: That's old school thinking, Lee. Like Ed said, we've got to keep it real. I submit that it's better to tweak the plan as we learn more and as changes are requested. It's way more realistic. What's the point of a plan if it doesn't reflect reality? Lee (frowning): I suppose so, but senior management's not going to like this ... they want a fixed plan. CS550 Intro. to SE Spring 2007 Doug (smiling): Then you'll have to reeducate them, buddy. 8 Considering Agile Software Development (pg 113-114) Doug: And? The scene:
The players: Doug Miller's office. Doug Miller, software engineering manager; Jamie Lazar, software team member; Vinod Raman, software team member. The conversation: (A knock on the door) Jamie: Doug, you got a minute? Doug: Sure Jamie, what's up? Jamie: We've been thinking about our process discussion yesterday ... you know, what process we're going to choose for this new SafeHome project. CS550 Intro. to SE Spring 2007 Vinod: I was talking to a friend at another company, and he was telling me about Extreme Programming. It's an agile process model, heard of it? Doug: Yeah, some good, some bad. Jamie: Well, it sounds pretty good to us. Lets you develop software really fast, uses something called
pair programming to do real-time quality checks ... it's pretty cool, I think. Doug: It does have a lot of really good ideas. I like the pair 9 programming concept, for instance, and the idea that stakeholders should be part of the team. Jamie: Huh? You mean that marketing will work on the project team with us? Doug (nodding): They're a stakeholder, aren't they? Jamie: Jeez ... they'll be requesting changes every five minutes. Vinod: Not necessarily. My friend said that there are ways to "embrace" changes during an XP project. CS550 Intro. to SE Spring 2007 Doug: So you guys think we should use XP? Jamie: It's definitely worth considering. Doug: I agree. And even if we choose an incremental model as our approach, there's no reason why we can't incorporate much
of what XP has to offer. Vinod: Doug, before you said "some good, some bad." What was the "bad"? Doug: The thing I don't like is the way XP downplays analysis and design ... sort of says that writing code is where the action is. 10 (The team members look at one another and smile.) Doug: So you agree with the XP approach? Jamie (speaking for both): Writing code is what we do, Boss! Doug (laughing): True, but I'd like to see you spend a little less time coding and then re-coding and a little more time analyzing what has to be done and designing a solution that works. Vinod: Maybe we can have it both ways, agility with a little discipline. CS550 Intro. to SE Spring 2007 Doug: I think we can, Vinod. In fact, I'm sure of it. 11 Communication Mistakes (pg135) The scene:
The players: Software engineering team workspace. Jamie Lazar, software team member; Vinod Raman, software team member; Ed Robbins software team member. The conversation: Ed: What have you heard about this SafeHome project? Vinod: The kick-off meeting is scheduled for next week. Jamie: I've already done a little bit of investigation, but it didn't go well." CS550 Intro. to SE Spring 2007 Ed: What do you mean? Jamie: Well, I gave Lisa Perez a call. She's the marketing honcho on this thing."
Vinod: And ... ? Jamie: I wanted her to tell me about SafeHome features and functions ... that sort of thing. Instead, she began asking me questions about security systems, surveillance systems ... I'm no expert. Vinod: What does that tell you? (Jamie shrugs.) Vinod: That marketing will need 12 us to act as consultants and that we'd better do some homework on this product area before our kick-off meeting. Doug said that he wanted us to "collaborate" with our customer, so we'd better learn how to do that. Ed: Probably would have been better to stop by her office. Phone calls just don't work as well for this sort of thing. Jamie: You're both right. We've got to get our act together or our early communications will be a struggle. CS550 Intro. to SE Spring 2007 Vinod: I saw Doug reading a book on "requirements engineering." I'll bet that lists some principles of good communication. I'm going to borrow it from him. Jamie: Good idea ... then you can teach us. Vinod (smiling): Yeah,
right. 13 Preliminary System Engineering (pg163-164) Jamie: That's why we have The scene: The players: Software engineering team workspace after the SafeHome kickoff meeting has occurred. Jamie Lazar, software team member; Vinod Raman, software team member; Ed Robbins, software team member. The conversation: Ed: I think it went pretty well. Vinod: Yeah ... but all we did was look at the overall system-we've got plenty of requirements gathering work left to do for the software. CS550 Intro. to SE Spring 2007 additional meetings scheduling for the next five days. By the way, I suggested that two of the "customers" move over here for the next few weeks. You know,
live with us so we can really communicate, er, collaborate. Vinod: How did that go? Jamie: Well, they looked at me like I was crazy, but Doug [the software engineering manager] likes the idea--it's agile--so he's talking to them. Ed: I was taking notes using my PDA during the meeting, and I 14 came up with a list of basic functions. Jamie: Cool, let's see. Ed: I've already e-mailed both of you a copy. Take a look and we'll talk. Vinod: How about after lunch? (Jamie and Vinod received the following from Ed) Preliminary notes of the structure/functionality of SafeHome: The system will make use of one or more PCs, various wall-mounted and/or handheld control CS550 Intro. to SE Spring 2007 panels, various sensors, and
applicance/device controllers. All will communicate via wireless protocols (e.g., 802.11b) and will be designed for new-home construction and for application within existing homes. All hardware with the exception of our new wireless box will be off the shelf. Basic software functionality that I could glean from our kickoff conversation. Home security functions: Standard window/door/motion sensor monitoring for unauthorized access (break-ins). Monitoring for fire, smoke, and CO levels. 15 Monitoring for water levels in basement (e.g., flood or broken water heater). Monitoring for outside movement. Change security setting via the Internet. Home surveillance functions: Connect to one or more video cameras placed inside/outside
house. Control pan/zoom for cameras. Define camera monitoring zones. Display camera views on PC. Access camera views via the Internet. Selectively record camera output digitally. Replay camera output. CS550 Intro. to SE Spring 2007 Home management functions: Control lighting. Control appliances. Control HVAC. Control video/audio equipment throughout house. Ability to set house for "vacation/travel mode" with one button sets. Set appliances/lighting/HVAC accordingly. Set answering machine message. Contacts vendors to stop paper, mail, etc. 16 Communication management functions:
Answering machine functions. List of callers via caller ID. Messages, time-stamped. Message text via voice recognition system. E-mail functions (all standard email functions). Standard e-mail display. Voice read of e-mail via phone access. Personal phone book. Link to PDA. CS550 Intro. to SE Spring 2007 Other functions: As yet undefined. All functions are accessible via the Internet with appropriate password protection. 17 Conducting a Requirements Gathering Meeting (pg188) The conversation: The scene: The scene: A meeting room. The first requirements gathering meeting is in progress. The players:
Jamie Lazar, software team member; Vinod Raman, software team member; Ed Robbins, software team member; Doug Miller, software engineering manager; three members of marketing; a product engineering representative; a facilitator. CS550 Intro. to SE Spring 2007 Facilitator (pointing at white board): So that's the current list of objects and services for the home security function. Marketing person: That about covers it from our point of view. Vinod: Didn't someone mention that they wanted all SafeHome functionality to be accessible via the Internet? That would include the home security function, no? Marketing person: Yes, that's right ... we'll have to add that functionality and the appropriate objects. 18
Facilitator: Does that also add some constraints? Jamie: It does, both technical and legal. Production rep: Meaning? Jamie: We better make sure an outsider can't hack into the system, disarm it, and rob the place or worse. Heavy liability on our part. Doug: Very true. Marketing: But we still need Internet connectivity . just be sure to stop an outsider from getting in. CS550 Intro. to SE Spring 2007 Ed: That's easier said than done and.... Facilitator (interrupting): I don't want to debate this issue now. Let's note it as an action item and proceed. (Doug, serving as the recorder for the meeting, makes an appropriate note.) Facilitator: I have a feeling there's still more to consider here. (The group spends the next 45 minutes refining and ex panding the details of the home security function.) 19
Developing a Preliminary User Scenario (pg190) The scene: A meeting room, continuing the first requirements gathering meeting. The players: Jamie Lazar, software team member; Vinod Raman, software team member; Ed Robbins, software team member; Doug Miller, software engineering manager; three members of marketing; a product engineering representative; a facilitator. CS550 Intro. to SE Spring 2007 The conversation: Facilitator: We've been talking
about security for access to SafeHome functionality that will be accessible via the Internet. I'd like to try something. Let's develop a user scenario for access to the home security function. Jamie: How? Facilitator: We can do it a couple of different ways, but for now, I'd like to keep things really informal. Tell us (he points at a marketing person) how you envision accessing the system. 20 Marketing person: Um. .. , well, this is the kind of thing I'd do if I was away from home and I had to let someone into the house, say a housekeeper or repair guy, who didn't have the security code. Facilitator (smiling): That's the reason you'd do it .. . tell me how you'd actually do this. Marketing person: Um . . . the first thing I'd need is a PC. I'd log on to a Web site we'd maintain for all users of SafeHome. I'd provide my user id and ... CS550 Intro. to SE Spring 2007 Vinod (interrupting): The Web page would have to be
secure, encrypted, to guarantee that we're safe and.... Facilitator (interrupting): That's good information, Vinod, but it's technical. Let's just focus on how the end-user will use this capability, OK? Vinod: No problem. Marketing person: So, as I was saying, I'd log on to a Web site and provide my user id and two levels of passwords. Jamie: What if I forget my password? 21 Facilitator (interrupting): Good point, Jamie, but let's not address that now. We'll make a note of that and call it an "exception." I'm sure there'll be others. Marketing person: After I enter the passwords, a screen representing all SafeHome functions will appear. I'd select the home security function. The system might request that I verify who I am, say by asking for my address or phone number or something. It would then display a picture of the CS550 Intro. to SE Spring 2007 security system control panel along with a list of functions that I can perform--arm the system, disarm the system, disarm one or more sensors. I suppose it might also allow me to reconfigure security zones and other things like that, but I'm not sure. (As the marketing person continues talking, Doug takes co
pious notes. These form the basis for the first informal use-case scenario. Alternatively, the marketing person could have been asked to write the scenario, but this would be done outside the meeting.) 22 Developing a High-Level Use-Case Diagram (pg195) The scene: A meeting room, continuing the requirements gathering meeting. The players: Jamie Lazar, software team member; Vinod Raman, software team member; Ed Robbins, software team member; Doug Miller, software engineering manager; three members of marketing; a product engineering representative; a facilitator. CS550 Intro. to SE
Spring 2007 The conversation: Facilitator: We've spent a fair amount of time talking about SafeHome home security functionality. During the break I sketched a use-case diagram to summarize the important scenarios that are part of this function. Take a look. (All attendees look at Figure 7.3.) Jamie: I'm just beginning to learn UML notation. So the home security function is represented by the big box with the ovals inside it? And the 23 ovals represent use-cases that we've written in text? Facilitator: Yep. And the stick figures represent actors--the people or things that interact with the system as described by the use-case ... oh, I use the labeled square to represent an actor that's not a person, in this case, sensors. Doug: Is that legal in UML? Facilitator: Legality isn't the issue. The point is to communicate information. I view the use of a human-like stick figure for representing a device to be misleading. So I've CS550 Intro. to SE Spring 2007
adapted things a bit. I don't think it creates a problem. Vinod: Okay, so we have usecase narratives for each of the ovals. Do we need to develop the more detailed template-based narratives I've read about? Facilitator: Probably, but that can wait until we've considered other SafeHome functions. Marketing person: Wait, I've been looking at this diagram, and all of a sudden I realize we missed something. Facilitator: Oh really. Tell me what we've missed. (The meeting continues.) 24 Preliminary Behavioral Modeling (pg199) The conversation: The scene: A meeting room, continuing the requirements meeting. The players:
Jamie Lazar, software team member; Vinod Raman, software team member; Ed Robbins, software team member; Doug Miller, software engineering manager; three members of marketing; a product engineering representative; a facilitator. CS550 Intro. to SE Spring 2007 Facilitator: We've just about finished talking about SafeHome home security functionality. But before we do, I want to discuss the behavior of the function. Marketing person: I don't understand what you mean by behavior. Ed (laughing): That's when you give the product a "timeout" if it misbehaves. Facilitator: Not exactly. Let me explain. (The facilitator explains the 25 basics of behavioral modeling to the requirements gathering team.)
Marketing person: This seems a little technical. I'm not sure I can help here. Facilitator: Sure you can. What behavior do you observe from the user's point of view? Marketing person: Uh... , well the system will be monitoring the sensors. It'll be reading commands from the homeowner. It'll be displaying its status. CS550 Intro. to SE Spring 2007 Facilitator: See, you can do it. Jamie: It'll also be polling the PC to determine if there is any input from it, for example Internet-based access or configuration information. Vinod: Yeah, in fact, configuring the system is a state in its own right. Doug: You guys are rolling. Let's give this a bit more thought . . . Is there a way to diagram this stuff? Facilitator: There is, but let's postpone that until after the meeting. 26 The Start of a Negotiation (pg202203)Lisa (smiling): Yeah, they The scene:
The players: Lisa Perez's office, after the first requirements gathering meeting. Doug Miller, software engineering manager Lisa Perez, marketing manager. The conversation: Lisa: So, I hear the first meeting went really well. Doug: Actually, it did. You sent some good people to the meeting ... they really contributed. CS550 Intro. to SE Spring 2007 actually told me they got into it, and it wasn't a propeller head activity. Doug (laughing): I'll be sure to take off my techie beanie the next time I visit ... Look, Lisa, I think we may have a problem with getting all of the functionality for the home security function out by the dates your management is talking about. It's early, I know, but I've already been doing a little back of the envelope planning and.... 27
Lisa: We've got to have it by that date, Doug. What functionality are you talking about? Doug: I figure we can get full home security functionality out by the drop-dead date, but we'll have to delay Internet access till the second release. Lisa: Doug, it's the Internet access that gives SafeHome "gee whiz" appeal. We're going to build our entire marketing campaign around it. We've gotta have it! CS550 Intro. to SE Spring 2007 Doug: I understand your situation, I really do. The problem is that in order to give you Internet access, we'll need a fully secure Web site up and running. That takes time and people. We'll also have to build a lot of additional functionality into the first release . . . I don't think we can do it with the resources we've got. Lisa (frowning): I see, but you've got to figure out a way to get it done. It's pivotal to home security functions and to other functions as well ... the other 28 functions can wait until the next releases . . . I'll agree to that. Lisa and Doug appear to be at an impasse, and yet they must negotiate a solution to this problem. Can they both
"win" here? Playing the role of a mediator, what would you suggest? CS550 Intro. to SE Spring 2007 29 Developing Another Preliminary User Scenario (pg219) SafeHome surveillance The scene: The players: A meeting room, during the second requirements gathering meeting. Jamie Lazar, software team member; Ed Robbins, software team member; Doug Miller, software engineering manager; three members of marketing; a product engineering representative; a facilitator. The conversation: Facilitator: It's time that we begin talking about the CS550 Intro. to SE Spring 2007
function. Let's develop a user scenario for access to the home security function. Jamie: Who plays the role of the actor on this? Facilitator: I think Meredith (a marketing person) has been working on that functionality. Why don't you play the role. Meredith: You want to do it the same way we did it last time, right? Facilitator: Right ... same way. Meredith: Well, obviously the reason for surveillance is to 30 allow the homeowner to check out the house while he or she is away, to record and play back video that is captured ... that sort of thing. Ed: Will the video be digital, and will it be stored on disk? Facilitator: Good question, but let's postpone implementation issues for now. Meredith? Meredith: Okay, so basically there are two parts to the surveillance function ... the first configures the system including laying out a floor plan--we need tools to help the CS550 Intro. to SE Spring 2007
homeowner do this--and the second part is the actual surveillance function itself. Since the layout is part of the configuration activity, I'll focus on the surveillance function. Facilitator (smiling): Took the words right out of my mouth. Meredith: Um ... I want to gain access to the surveillance function either via the PC or via the Internet. My feeling is that the Internet access would be more frequently used. Anyway, I want to be able to display camera views on a PC and 31 control pan and zoom for a specific camera. I specify the camera by selecting it from the house floor plan. I want to selectively record camera output and replay camera output. I also want to be able to block access to one or more cameras with a specific password. And I want the option of seeing small windows that show views from all cameras and then be able to pick the one I want enlarged. Jamie: Those are called thumbnail views. CS550 Intro. to SE Spring 2007 Meredith: Okay, then I want thumbnail views from all the cameras. I also want the interface to the surveillance function to have the same look and feel as all other SafeHome interfaces. I want
it to be intuitive, meaning I don't want to have to read a manual to use it. Facilitator: Good job, now, let's go into this function in a bit more detail.... 32 Use-Case Template for Surveillance (pg222223) Use-case: Primary actor: To view output of camera placed throughout the house from any remote location via the Internet. Preconditions: Homeowner. Goal in context: Access camera surveillance-display camera views (ACS-DCV). System must be fully configured; appropriate user ID and passwords must be obtained. Trigger: The homeowner decides to take a look inside the house while away. CS550 Intro. to SE Spring 2007
Scenario: 1. 2. 3. 4. 5. 6. 7. 8. The homeowner logs onto the SafeHome Products Web site. The homeowner enters his or her user ID. The homeowner enters two passwords (each at least eight characters in length). The system displays all major function buttons. The homeowner selects "surveillance" from the major function buttons. The homeowner selects "pick a camera." The system displays the floor plan of the house. The homeowner selects a camera icon from the floor plan. 33 9. 10. 11. The homeowner selects the "view" button. The system displays a viewing window that is identified by the camera ID. The system displays video output
within the viewing window at one frame per second. 3. 4. Exceptions: 1. 2. ID or passwords are incorrect or not recognizedsee use-case: "validate ID and passwords." Surveillance function not configured for this system-system displays appropriate error message; see use-case: "configure surveillance function." 5. Priority: Moderate priority, to be implemented after basic functions. CS550 Intro. to SE Spring 2007 Homeowner selects "view thumbnail snapshots for all cameras"--see use-case: "view thumbnail snapshots for all cameras." A floor plan is not available or has not been configured--display appropriate error message and see use-case: "configure floor plan." An alarm condition is encountered--see use-case: "alarm condition encountered." When available: Third increment. Frequency of use: Infrequent. 34
Channel to actor: Via PC-based browser and Internet connection to SafeHome Web site. 1. 2. Secondary actors: System administrator, cameras. Channels to secondary actors: 1. 2. System administrator: PC-based system Cameras: wireless connectivity 3. Is security sufficient? Hacking into this feature would represent a major invasion of privacy. Will system response via the Internet be acceptable given the bandwidth required for camera views? Will we develop a capability to provide video at a higher framesper-second rate when high bandwidth connections are available? Open issues: 1. What mechanisms protect unauthorized use of this capability by employees of the company? CS550 Intro. to SE
Spring 2007 35 Data Flow Modeling (pg231-232) The scene: Jamie's cubicle, after the last requirements gathering meeting has concluded. The players: Jamie, Vinod, Ed all members of the SafeHome software engineering team. The conversation: (Jamie has sketched out the models shown in Figures 8.9 through 8.12 and is showing them to Ed and Vinod.) CS550 Intro. to SE Spring 2007 Jamie: I took a software engineering course in college, and they taught us this stuff. The prof said it's a bit old fashioned, but you know what? It helps me to clarify things. Ed: That's cool. But I don't see
any classes or objects here. Jamie: No ... this is just a flow model with a little behavioral stuff thrown in. Vinod: So these DFDs represent an I-P-O view of the software, right? Ed: I-P-O? 36 Vinod: Input-process-output. The DFDs are actually pretty intuitive ... if you look at 'em for a moment, they show how data objects flow through the system and get transformed as they go. Ed: Looks like we could convert every bubble into an executable component . . . at least at the lowest level of the DFD. Jamie: That's the cool part, you can. In fact there's a way to translate the DFDs into a design architecture. Ed: Really? CS550 Intro. to SE Spring 2007 Jamie: Yeah, but first we've got to develop a complete analysis model, and this isn't it. Vinod: Well, it's a first step, but we're going to have to address class-based elements
and also behavior aspects, although this state diagram does some of that. Ed: We've got a lot of work to do and not much time to do it. (Doug--the software engineering manager--walks into the cubical.) 37 Doug: So the next few days will be spent developing the analysis model, huh? Jamie (looking proud): We've already begun. Doug: Good, we've got a lot of work to do and not much time to do it. (The three software engineers look at one another and smile.) CS550 Intro. to SE Spring 2007 38 Class Models (pg238-239) The scene: The players: Ed's cubicle, as analysis modeling begins.
Jamie, Vinod, Ed all members of the SafeHome software engineering team. The conversation: (Ed has been working to extract classes from the usecase template for Access camera surveillance-display camera views" [presented in an earlier sidebar in this chapter] and is presenting the classes he has extracted to his colleagues.) CS550 Intro. to SE Spring 2007 Ed: So when the homeowner wants to pick a camera, he or she has to pick it from a floor plan. I've defined a FloorPlan class. Here's the diagram. (They look at Figure 8.14.) Jamie: So FloorPlan is a class that is put together with walls that are composed of wall segments, doors and windows, and also cameras; that's what those labeled lines mean, right? Ed: Yeah, they're called "associations." One class is associated with another according to the associations 39 I've shown. [Associations are discussed in Section 8.7.5.] Vinod: So the actual floor plan is made up of walls and contains cameras and sensors that are placed within those
walls. How does the floor plan know where to put those objects? Ed: It doesn't, but the other classes do. See the attributes under, say, WallSegment, which is used to build a wall. The wall segment has start and stop coordinates and the draw () operation does the rest. CS550 Intro. to SE Spring 2007 Jamie: And the same goes for windows and doors. Looks like camera has a few extra attributes. Ed: Yeah, I need them to provide pan and zoom info. Vinod: I have a question. Why does the camera have an ID but the others don't? Ed: We'll need to identify each camera for display purposes. Jamie: Makes sense to me, but I do have a few more questions. 40 (Jamie asks questions which result in minor modifications.) Vinod: Do you have CRC cards for each of the classes?
If so, we ought to role play through them, just make sure nothing has been omitted. Ed:" I'm not quite sure how to do them. Vinod: It's not hard, and they really pay off. I'll show you. CS550 Intro. to SE Spring 2007 41 CRC models (pg 245-246) The scene: Ed's cubicle, as analysis modeling continues. The players: Vinod, Ed members of the SafeHome software engineering team. The conversation: (Vinod has decided to show Ed how to develop CRC cards by showing him an example.) Vinod: While you've been working on surveillance and Jamie has been tied up with security, I've been working on the home management function. CS550 Intro. to SE Spring 2007
Ed: What's the status of that? Marketing kept changing its mind. Vinod: Here's the first cut usecase for the whole function ... we've refined it a bit, but it should give you an overall view. Use-case: SafeHome home management function. Narrative: We want to use the home management interface on a PC or an Internet connection to control electronic devices that have wireless interface controllers. The system should allow me to turn specific lights 42 on and off, to control appliances that are connected to a wireless interface, to set my heating and air conditioning system to temperatures that I define. To do this, I want to select the devices from a floor plan of the house. Each device must be identified on the floor plan. As an optional feature, I want to control all audiovisual devices--audio, television, DVD, digital recorders, and so forth. With a single selection, I want to be able to set the entire house for various situations. CS550 Intro. to SE Spring 2007 One is home, another is away, a third is overnight travel, and a fourth is extended travel. All of these situations will have settings that will be applied to all devices. In the overnight travel and extended travel states, the system should turn lights on and off at random intervals (to make it look like someone is home) and control
the heating and air conditioning system. I should be able to override these settings via the Internet with appropriate password protection. 43 Ed: The hardware guys have got all the wireless interfacing figured out? Vinod (smiling): They're working on it, say it's no biggy. Anyway, I extracted a bunch of classes for home management, and we can use one as an example. Let's use the HomeManagementlnterface class. Ed: Okay . . . so the responsibilities are ... the attributes and operations for the class, and the collaborations are the classes that the responsibilities point to. CS550 Intro. to SE Spring 2007 Vinod: I thought you didn't understand CRC. Ed: Maybe a little, but go ahead. Vinod: So here's my class definition for HomeManagementlnterface. Attributes:
optionsPanel--provides info on buttons that enable user to select functionality situationPanel--provides info on buttons that enable user to select situation FloorPlan--same as surveillance object but this one displays devices 44 devicelcons--info on icons representing lights, appliances, HVAC, etc. devicePanels--simulation of appliance or device control panel; allows control Operations: displayControl(), selectControl(), displaySituation(), selectSituation(), accessFloorplan(), selectDevicelcon(), displayDevicePanel(), accessDevicePanel(), . . . Class: Responsibility Collaborator
displayControl OptionsPanel (class) selectControl OptionsPanel (class) displaySituation SituationPanel (class) selectSituation SituationPanel (class) accessFloorplan FloorPlan (class) ... HomeManagementInterface CS550 Intro. to SE Spring 2007 45 Ed: So when the operation accessFloorplan() is invoked, it collaborates with the FloorPlan object just like the one we developed for surveillance. Wait, I have a description of it here. (They look at Figure 8.14.) Vinod: Exactly. And if we wanted to review the entire class model, we could start with this index card, then go to the collaborator's index card, and from there to one of the collaborator's collaborators, and so on. CS550 Intro. to SE Spring 2007
Ed: Good way to find omissions or errors. Vinod: Yep. 46 Design Concepts (pg270-271) The scene: The players: Vinod's cubicle, as design modeling begins. Vinod, Jamie, Ed members of the SafeHome software engineering team . Also, Shakira, a new member of the team. The conversation: (All four team members have just returned from a morning seminar, entitled "Applying Basic Design Concepts," offered by a local computer science professor.) CS550 Intro. to SE Spring 2007 Vinod: Did you get anything out of the seminar? Ed: Knew most of the stuff,
but it's not a bad idea to hear it again, I suppose. Jamie: When I was an undergrad CS major, I never really understood why information hiding was as important as they say it is. Vinod: Because ... bottom line ... it's a technique for reducing error propagation in a program. Actually, functional independence also accomplishes the same thing. 47 Shakira: I wasn't a CS grad, so a lot of the stuff the instructor mentioned is new to me. I can generate good code and fast. I don't see why this stuff is so important. Jamie: I've seen your work, Shak, and you know what, you do a lot of this stuff naturally ... that's why your designs and code work. Shakira (smiling): Well, I always do try to partition the code, keep it focused on one thing, keep interfaces simple and constrained, reuse code CS550 Intro. to SE Spring 2007 whenever I can that sort of thing. Ed: Modularity, functional
independence, hiding, patterns ... see. Jamie: I still remember the very first programming course I took ... they taught us to refine the code iteratively. Vinod: Same thing can be applied to design, you know. Ed: The only concept I hadn't heard of before was "refactoring." Shakira: That's used in Extreme Programming, I think she said. 48 Ed: Yep. It's not a whole lot different than refinement, only you do it after the design or code is completed. Kind of an optimization pass through the software, if you ask me. Jamie: Let's get back to SafeHome design. I think we should put these concepts on our review checklist as we develop the design model for SafeHome. Vinod: I agree. But as important, let's all commit to think about them as we develop the design. CS550 Intro. to SE Spring 2007 49 Refining an Analysis Class into a Design Class (pg273) The scene:
The players: Ed's cubicle, as design modeling continues. Vinod, Ed members of the SafeHome software engineering team. The conversation: (Ed is working on the FloorPlan class [see sidebar discussion in Section 8.7.4 and Figure 8.14] and has refined it for the design model.) Ed: So you remember the FloorPlan class, right? It's used CS550 Intro. to SE Spring 2007 as part of the surveillance and home management functions. Vinod (nodding): Yeah, I seem to recall that we used it as part of our CRC discussions for home management. Ed: We did. Anyway, I'm refining it for design. Want to show how we'll actually implement the FloorPlan class. My idea is to implement it as a set of linked lists [a specific data structure]. So ... I had to refine the analysis class FloorPlan (Figure 8.14) and, actually, sort of simplify it. 50
Vinod: The analysis class showed only things in the problem domain, well, actually on the computer screen, that were visible to the end-user, right? Ed: Yep, but for the FloorPlan design class, I've got to add some things that are implementation specific. I needed to show that FloorPlan is an aggregation of segments-hence the Segment class--and that the Segment class is composed of lists for wall segments, windows, doors, and so on. The class Camera CS550 Intro. to SE Spring 2007 collaborates with FloorPlan, and obviously, there can be many cameras in the floor plan. Vinod: Phew, let's see a picture of this new FloorPlan design class. (Ed shows Vinod the drawing shown in Figure 9.3.) Vinod: Okay, I see what you're trying to do. This allows you to modify the floor plan easily because new items can be added or deleted to the list--the aggregation--without any problems. Ed (nodding): Yeah, I think it'll work. Vinod: So do I. 51 Choosing an Architectural Style (pg295-296) Jamie: But . . . ?
The scene: The players: Jamie's cubicle, as design modeling continues. Jamie, Ed members of the SafeHome software engineering team. The conversation: Ed (frowning): We've been modeling the security function using UML. . . you know classes, relationships, that sort of stuff. So I guess the object-oriented architecture' is the right way to go. CS550 Intro. to SE Spring 2007 Ed: But . . . I have trouble visualizing what an objectoriented architecture is. I get the call and return architecture, sort of a conventional process hierarchy, but 00 .. I don't know. It seems sort of amorphous. Jamie (smiling): Amorphous, huh? Ed: Yeah . . . what I mean is I can't visualize a real structure, just design classes floating in space. Jamie: Well, that's not true.
There are class hierarchies . . . 52 think of the hierarchy (aggregation) we did for the FloorPlan object [Figure 9.3]. An 00 architecture is a combination of that structure and the interconnectionsyou know, collaborations--between the classes. We can show it by fully describing the attributes and operations, the messaging that goes on, and the structure of the classes. Ed: I'm going to spend an hour mapping out a call and return architecture, then I'll go back and consider an 00 architecture. CS550 Intro. to SE Spring 2007 Jamie: Doug'Il have no problem with that. He said that we should consider architectural alternatives. By the way, there's absolutely no reason why both of these architectures couldn't be used in combination with one another. Ed: Good. I'm on it. 53 Architecture Assessment (pg305-306) The scene: The players:
Doug Miller's office as architectural design modeling proceeds. Vinod, Jamie, Shakira, Ed members of the SafeHome software engineering team. Doug Miller manager of the software engineering group. The conversation: Doug: I know you guys are deriving a couple of different architectures for the SafeHome CS550 Intro. to SE Spring 2007 product, and that's a good thing. I guess my question is, how are we going to choose the one that's best? Ed: I'm working on a call and return style, and then either Jamie or I are going to derive an 00 architecture. Doug: Okay, and how do we choose? Shakira: I took a course in design in my senior year, and I remember that there are a number of ways to do it. Vinod: There are, but they're a bit academic. Look, I think we 54
can do our assessment and choose the right one using usecases and scenarios. Doug: Isn't that the same thing? Vinod: Not when you're talking about architectural assessment. We already have a complete set of use-cases. So we apply each to both architectures and see how the system reacts--how components and connectors work in the use-case context. Ed: That's a good idea. Makes sure we didn't leave anything out. CS550 Intro. to SE Spring 2007 Vinod: True, but it also tells us whether the architectural design is convoluted, whether the system has to twist itself into a pretzel to get the job done. Jamie: Scenarios aren't just another name for use-cases? Vinod: No, in this case a scenario implies something different. Doug: You're talking about a quality scenario or a change scenario, right? Vinod: Yes. What we do is go back to the stakeholders and 55
ask them how SafeHome is likely to change over the next, say, three years. You know, new versions, features, that sort of thing. We build a set of change scenarios. We also develop a set of quality scenarios that define the attributes we'd like to see in the software architecture. Jamie: And we apply them to the alternatives. Vinod: Exactly. The style that handles the use-cases and scenarios best is the one we choose. CS550 Intro. to SE Spring 2007 56 Refining a First-Cut Architecture (pg315) (Ed shows Jamie Figure 10.17, The scene: The players: Jamie's cubicle, as design modeling continues. Jamie, Ed members of the SafeHome software engineering team. The conversation: (Ed has just completed a firstcut design of the monitor sensors subsystem. He stops in to ask Jamie her opinion.) Ed: So here's the architecture that I derived. CS550 Intro. to SE
Spring 2007 which she studies for a few moments.) Jamie: That's cool, but I think we can do a few things to make it simpler ... and better. Ed: Such as? Jamie: Well, why did you use the sensor input controller component? Ed: Because you need a controller for the mapping. Jamie: Not really. The controller doesn't do much, since we're managing a single flow path for 57 incoming data. We can eliminate the controller with no ill effects. Ed: I can live with that, I'll make the change and ... Jamie (smiling): Hold up! We can also implode the components establish alarm conditions and select phone number. The transform controller you show isn't really necessary, and the small decrease in cohesion is tolerable. Ed: Simplification, huh? CS550 Intro. to SE Spring 2007
Jamie: Yep. And while we're making refinements, it would be a good idea to implode the components format display and generate display. Display formatting for the control panel is simple. We can define a new module called produce display Ed (sketching): So this is what you think we should do? (He shows Jamie Figure 10.18.) Jamie: It's a start. 58 The OCP in Action (pg332) The scene: The players: Vinod's cubicle. Vinod, Shakira members of the SafeHome software engineering team. The conversation: Vinod: I just got a call from Doug [the team manager]. He says marketing wants to add a new sensor. Shakira (smirking): Not
again, jeez! Vinod: Yeah ... and you're not going to believe what these CS550 Intro. to SE Spring 2007 guys have come up with. Shakira: Amaze me. Vinod (laughing): They call it a doggie angst sensor. Shakira: Say what? Vinod: It's for people who leave their pets home in apartments or condos or houses that are close to one another. The dog starts to bark. The neighbor gets angry and complains. With this sensor, if the dog barks for more than, say, a minute, the sensor sets a special alarm mode that calls the owner on his or her cell phone. Shakira: You're kidding me, right? 59 Vinod: Nope. Doug wants to know how much time it's going to take to add it to the security function. Shakira (thinking a moment): Not much ... look. [She shows Vinod Figure 11.4] We've isolated the actual sensor classes behind the sensor interface. As long as we have specs for the doggie sensor, adding it should be a piece of cake. Only thing I'll have to do
is create an appropriate component ... uh, class, for it. No change to the Detector component at all. Vinod: So I'll tell Doug it's no big CS550 Intro. to SE Spring 2007 deal. Shakira: Knowing Doug, he'll keep us focused and not deliver the doggie thing until the next release. Vinod: That's not a bad thing, but can you implement now if he wants you to? Shakira: Yeah, the way we designed the interface lets me do it with no hassle. Vinod (thinking a moment): Have you ever heard of the "OpenClosed Principle"? Shakira (shrugging): Never heard of it. Vinod (smiling): Not a problem. 60 Cohesion in Action (pg336-337) The scene:
Jamie's cubicle. The players: Jamie, Ed members of the SafeHome software engineering team who are working on the surveillance function. The conversation: Ed: I have a first-cut design of the camera component. Jamie: Wanna do a quick review? Ed: I guess ... but really, I'd like your input on something. (Jamie gestures for him to continue.) CS550 Intro. to SE Spring 2007 Ed: We originally defined five operations for camera. Look ... [shows Jamie the list] determineType() tells me the type of camera. translateLocation() allows me to move the camera around the floor plan. displayID() gets the camera ID and displays it near the camera icon. displayView() shows me the field of view of the camera graphically. displayZoom() shows me the magnification of the camera graphically.
Ed: I've designed each separately, and they're pretty simple operations. So I thought 61 it might be a good idea to combine all of the display operations into just one that's called displayCamera()--it'll show the ID, the view, and the zoom. Whaddaya think? Jamie (grimacing): Not sure that's such a good idea. Ed (frowning): Why? All of these little ops can cause headaches. Jamie: The problem with combining them is we lose cohesion. You know, the displayCamera() op won't be single-minded. CS550 Intro. to SE Spring 2007 Ed (mildly exasperated): So what? The whole thing will be less than 100 source lines, max. It'll be easier to implement, I think. Jamie: And what if marketing decides to change the way that we represent the view field? Ed: I'll just jump into the displayCamera() op and make the mod.
Jamie: What about side effects? Ed: Whaddaya mean? Jamie: Well, say you make the change but inadvertently create a problem with the ID display. 62 Ed: I wouldn't be that sloppy. Jamie: Maybe not, but what if some support person two years from now has to make the mod. He might not understand the op as well as you do and, who knows, he might be sloppy. Ed: So you're against it? Jamie: You're the designer . . . it's your decision . . . just be sure you understand the consequences of low cohesion. Ed (thinking a moment): Maybe we'll go with separate display ops. CS550 Intro. to SE Spring 2007 Jamie: Good decision. 63 Coupling in Action (pg338-339) The scene:
Shakira's cubicle. The players: Vinod, Shakira members of the SafeHome software engineering team who are working on the security function. The conversation: Shakira: I had what I thought was a great idea ... then I thought about it a little, and it seemed like a not-sogreat idea. I finally rejected it, but I just thought I'd run it by you. Vinod: Sure, what's the idea? CS550 Intro. to SE Spring 2007 Shakira: Well, each of the sensors recognizes an alarm condition of some kind, right? Vinod (smiling): That's why we call them sensors, Shakira. Shakira (exasperated): Sarcasm, Vinod. You've got to work on your interpersonal skills. Vinod: You were saying? Shakira: Okay, anyway, I figured ... why not create an operation within each sensor object called makeCall() that would collaborate directly with the OutgoingCall component, well, with an interface to the OutgoingCall component. 64
Vinod (pensive): You mean rather than having that collaboration occur out of a component like ControlPanel or something? Shakira: Yeah ... but then I said to myself, that means that every sensor object will be connected to the OutgoingCall component, and that means that it's indirectly coupled to the outside world and . . . well, I just thought it made things complicated. Vinod: I agree. In this case, it's a better idea to let the sensor interface pass info to the ControlPanel and let it initiate the CS550 Intro. to SE Spring 2007 outgoing call. Besides, different sensors might result in different phone numbers. You don't want the sensor to store that information because if it changes. Shakira: It just didn't feel right. Vinod: Design heuristics for coupling tell us it's not right. Shakira: Whatever. 65 Violating a UI "Golden Rule (pg359360) Jamie: Well, what if we The scene:
The players: Vinod's cubicle, as user interface design begins. Vinod, Jamie members of the SafeHome software engineering team. The conversation: Jamie: I've been thinking about the surveillance function interface. Vinod (smiling): Thinking is good. Jamie: I think maybe we can simplify matters some. Vinod: Meaning? CS550 Intro. to SE Spring 2007 eliminate the floor plan entirely? It's flashy, but it's going to take serious development effort. Instead we just ask the user to specify the camera he wants to see and then display the video in a video window. Vinod: How does the homeowner remember how many cameras are set up and where they are? Jamie (mildly irritated): He's the homeowner, he should know. Vinod: But what if he doesn't? Jamie: He should.
66 Vinod: That's not the point ... what if he forgets? Jamie: Uh, we could provide a list of operational cameras and their locations. Vinod: That's possible, but why should he have to ask for a list? Jamie: Okay, we provide the list whether he asks or not. Vinod: Better. At least he doesn't have to remember stuff that we can give him. Jamie (thinking for a moment): But you like the floor plan, don't you? CS550 Intro. to SE Spring 2007 Vinod: Uh huh. Jamie: Which one will marketing like, do you think? Vinod: You're kidding, right? Jamie: No. Vinod: Duh ... the one with the flash ... they love sexy product features ... they're
not interested in which is easier to build. Jamie (sighing): Okay, maybe I'll prototype both. Vinod: Good idea ... then we let the customer decide. 67 Use-Cases for UI Design (pg368) The scene: Vinod's cubicle, as user interface design continues. The players: Vinod, Jamie members of the SafeHome software engineering team. The conversation: Jamie: I pinned down our marketing contact and had her write a use-case for the surveillance interface. Vinod: From who's point of view? Jamie: The home owner's, who else is there? CS550 Intro. to SE Spring 2007
Vinod: There's also the system administrator role. Even if it's the homeowner playing the role, it's a different point of view. The "administrator" sets the system up, configures stuff, lays out the floor plan, places the cameras ... Jamie: All I had marketing do was play the role of a homeowner who wants to see video. Vinod: That's okay. It's one of the major behaviors of the surveillance function interface. But we're going to have to 68 examine the system administration behavior as well. Jamie (irritated): You're right. (Jamie leaves to find the marketing person. She returns a few hours later.) Jamie: I was lucky. I found our marketing contact and we worked through the administrator use-case together. Basically, we're going to define "administration" as one function that's applicable to all other SafeHome functions. Here's what we came up with. CS550 Intro. to SE Spring 2007 (Jamie shows the informal usecase to Vinod.) Informal use-case: I want to be able to set or edit the system layout at any time. When I set up the system, I select an administration function. It asks me whether I want to do a new
set-up, or whether I want to edit an existing set-up. If I select a new set-up, the system displays a drawing screen that will enable me to draw the floor plan onto a grid. There will be icons for walls, windows, and doors so that drawing is easy. I just 69 stretch the icons to their appropriate lengths. The system will display the lengths in feet or meters (I can select the measurement system). I can select from a library of sensors and cameras and place them on the floor plan. I get to label each, or the system will do automatic labeling. I can establish settings for sensors and cameras from appropriate menus. If I select edit, I can move sensors or cameras, add new ones or delete existing ones, edit the floor plan, and CS550 Intro. to SE Spring 2007 edit the setting for cameras and sensors. In every case, I expect the system to do consistency checking and to help me avoid mistakes. Vinod (after reading the scenario): Okay, there are probably some useful design patterns or reusable components for GUIs for drawing programs. I'll betcha 50 bucks we can implement some or most of the administrator interface using them. Jamie: Agreed. I'll check it out. 70
Preparing for Testing (pg392) The scene: The players: Doug Miller's office, as component-level design continues and construction of certain components begins. Doug Miller software engineering manager; Vinod, Jamie, Ed, Shakira members of the SafeHome software engineering team. The conversation: Doug: It seems to me that we haven't spent enough time CS550 Intro. to SE Spring 2007 talking about testing. Vinod: True, but we've all been just a little busy. And besides, we have been thinking about it ... in fact, more than thinking. Doug (smiling): I know ... we're all overloaded, but we've still got to think down the line. Shakira: I like the idea of designing unit tests before I begin coding any of my components, so that's what I've been trying to do. I have a
pretty big file of tests to run once code for my components is complete. 71 Doug: That's an Extreme Programming [an agile software development process, see Chapter 4] concept, no? Ed: It is. Even though we're not using Extreme Programming per se, we decided that it would be a good idea to design unit tests before we build the componentthe design gives us all of the information we need. Jamie: I've been doing the same thing. Vinod: And I've taken on the role of the integrator, so every time one of the guys passes a CS550 Intro. to SE Spring 2007 component to me, I'll integrate it and run a series of regression tests on the partially integrated program. I've been working to design a set of appropriate tests for each function in the system. Doug (to Vinod): How often will you run the tests? Vinod: Every day ... until the system is integrated ... well, I mean until the software increment we plan to deliver is integrated.
Doug: You guys are way ahead of me! Vinod (laughing): Anticipation is everything in the software biz, Boss. 72 Preparing for Validation (pg407-408) The scene: Doug Miller's office, as component-level design continues and construction of certain components begins. The players: Doug Miller software engineering manager, Vinod, Jamie, Ed, Shakira members of the SafeHome software engineering team. The conversation: Doug: The first increment will be ready for validation in what ... about three weeks? CS550 Intro. to SE Spring 2007 Vinod: That's about right.
Integration is going well. We're smoke testing daily, finding some bugs but nothing we can't handle. So far, so good. Doug: Talk to me about validation. Shakira: Well, we'll use all of the use-cases as the basis for our test design. I haven't started yet, but I'll be developing tests for all of the use-cases that I've been responsible for. Ed: Same here. Jamie: Me too, but we've got to get our act together for 73 acceptance testing and also for alpha and beta testing, no? Doug: Yes, In fact I've been thinking that we could bring in an outside contractor to help us with validation. I have the money in the budget ... and it would give us a new point of view. Vinod: I think we've got it under control. Doug: I'm sure you do, but an ITG gives us an independent look at the software. Jamie: We're tight on time here, Doug. I, for one, don't have the time to baby-sit anybody you bring in to do the job. CS550 Intro. to SE Spring 2007
Doug: I know, I know. But if an ITG works from requirements and use-cases, not too much baby sitting will be required. Vinod: I still think we've got it under control. Doug: I hear you, Vinod, but I'm going to overrule on this one. Let's plan to meet with the ITG rep later this week. Get 'em started and see what they come up with. Vinod: Okay, maybe it'll lighten the load a bit. 74 Debugging (pg413) The scene: The players: Ed's cubical as coding and unit testing is conducted. Ed, Shakira members of the SafeHome software engineering team. The conversation: Shakira (looking in through the entrance to the cubical): Hey ... where were you at lunch time? Ed: Right here ... working. Shakira: You look miserable ... what's the matter? Ed (sighing audibly): I've
been CS550 Intro. to SE Spring 2007 working on this
smiling broadly now, stands and walks out.) CS550 Intro. to SE Spring 2007 76 Designing Unique Tests (pg423) The scene: Vinod's cubical. The players: Vinod, Ed members of the SafeHome software engineering team. The conversation: Vinod: So these are the test cases you intend to run for the password Validation operation. Ed: Yeah, they should cover pretty much all possibilities for the kinds of passwords a user might enter. CS550 Intro. to SE Spring 2007 Vinod: So let's see ... you note that the correct password will be
8080, right? Ed: Uh huh. Vinod: And you specify passwords 1234 and 6789 to test for errors in recognizing invalid passwords? Ed: Right, and I also test passwords that are close to the correct password, see ... 8081 and 8180. Vinod: Those are okay, but I don't see much point in running both the 1234 and 6789 inputs. They're redundant . . . test the same thing, don't they? 77 Ed: Well, they're different values. Vinod: That's true, but if 1234 doesn't uncover an error ... in other words ... the password Validation operation notes that it's an invalid password, it is not likely that 6789 will show us anything new. Ed: I see what you mean. Vinod: I'm not trying to be picky here ... it's just that we have limited time to do testing, so it's a good idea to run tests that have a high likelihood of finding new errors. CS550 Intro. to SE Spring 2007 Ed: Not a problem ... I'll give this a bit more thought. 78 Using Cyclomatic Complexity (pg428)
The scene: The players: Shakira's cubicle. Vinod,Shakira members of the SafeHome software engineering team who are working on test planning for the security function. The conversation: Shakira: Look ... I know that we should unit test al! the components for the security function, but there are a lot of 'em and if you consider the number of operations that have to be exercised, I don't know ... CS550 Intro. to SE Spring 2007 maybe we should forget whitebox testing, integrate everything, and start running black-box tests. Vinod: You figure we don't have enough time to do component tests, exercise the operations, and then integrate? Shakira: The deadline for the first increment is getting closer than I'd like ... yeah, I'm concerned. Vinod: Why don't you at least run white-box tests on the operations that are likely to be the most error prone? 79
Shakira (exasperated): And exactly how do I know which are likely to be the most error prone? Vinod: V of G. Shakira: Huh? Vinod: Cyclomatic complexity--V of G. Just compute V(G) for each of the operations within each of the components and see which have the highest values for V(G). They're the ones that are most likely to be error prone. Shakira: And how do I compute V of G? CS550 Intro. to SE Spring 2007 Vinod: It's really easy. Here's a book that describes how to do it. Shakira (leafing through the pages): Okay, it doesn't look hard. I'll give it a try. The ops with the highest V(G) will be the candidates for white-box tests. Vinod: Just remember that there are no guarantees. A component with a low V(G) can still be error prone. Shakira: Alright. But at least this'll help me to narrow down the number of components that have to undergo white-box testing. 80
Class Testing (pg447-448) The scene: Shakira's cubicle. The players: Jamie, Shakira members of the SafeHome software engineering team who are working on test case design for the security function. The conversation: Shakira: I've developed some tests for the Detector class [Figure 11.4]--you know, the one that allows access to all of the Sensor objects for the security function. You familiar with it? CS550 Intro. to SE Spring 2007 Jamie (laughing): Sure, it's the one that allowed you to add the "doggie angst" sensor. Shakira: The one and only. Anyway, it has an interface with four ops: read(), enable(), disable(), and test, Before a sensor can be read, it must be enabled. Once it's enabled, it can be read and tested. It can be disabled at any time, except if an alarm condition is being processed. So I defined a simple test sequence that will
exercise its behavioral life history. 81 (Shows Jamie the following sequence.) 1. Jamie: That'll work, but you've got to do more testing than that! Shakira: I know, I know. Here are some other sequences I've come up with. (She shows Jamie the following sequences.) 2. 3. 4. enable-test-read-disable enable-test-[read]*-test-disable [read]* enable-disable-[test | read] Jamie: So let me see if I understand the intent of these. #1 goes through a normal life CS550 Intro. to SE Spring 2007 history, sort of a conventional usage. #2 repeats the read operation n times, and that's a likely scenario. #3 tries to read the sensor before it's been enabled ... that should produce an error message of some kind, right? #4 enables and disables the sensor and then tries to read it. Isn't that the same as
test #3? Shakira: Actually no. In #4, the sensor has been enabled. What #4 really tests is whether the disable op works as it should. A read() or test() after disable() 82 should generate the error message. If it doesn't, then we have an error in the disable op. Jamie: Cool. Just remember that the four tests have to be applied for every sensor type since all the ops may be subtly different depending on the type of sensor. Shakira: Not to worry. That's the plan. CS550 Intro. to SE Spring 2007 83 Debating Product Metrics (pg471-472) The scene: The players: Vinod's cubicle. Vinod, Jamie, Ed members of the SafeHome software engineering team, who are continuing work on componentlevel design and test case design.
The conversation: Vinod: Doug [Doug Miller, software engineering manager] told me that we should all use product metrics, but he was kind of vague. He also said that he wouldn't push the matter ... using CS550 Intro. to SE Spring 2007 them was up to us. Jamie: That's good, 'cause there's no way I have time to start measuring stuff. We're fighting to maintain the schedule as it is. Ed: I agree with Jamie. We're up against it, here ... no time. Vinod: Yeah, I know, but there's probably some merit to using them. Jamie: I'm not arguing that, Vinod. It's a time thing ... and I for one don't have any to spare. Vinod: But what if measuring saves you time? 84 Ed: Wrong, it takes time and like Jamie said ... Vinod: No, wait ... what if it saves us time?
Jamie: How? Vinod: Rework ... that's how. If a metric we use helps us avoid one major or even moderate problem, and that saves us from having to rework a part of the system, we save time. No? Ed: It's possible, I suppose, but can you guarantee that some product metric will help us find a problem? Vinod: Can you guarantee that it CS550 Intro. to SE Spring 2007 won't? Jamie: So what are you proposing? Vinod: I think we should select a few design metrics, probably class-oriented, and use them as part of our review process for every component we develop. Ed: I'm not real familiar with class-oriented metrics. Vinod: I'll spend some time checking them out and make a recommendation ... okay with you guys? (Ed and Jamie nod without much enthusiasm.) 85 Applying CK Metrics (pg483-484) The scene:
Vinod's cubicle. The players: Vinod, Jamie, Shakira, Ed members of the SafeHome software engineering team, who are continuing work on componentlevel design and test case design. The conversation: Vinod: Did you guys get a chance to read the description of the CK metrics suite I sent you on Wednesday and make those measurements? CS550 Intro. to SE Spring 2007 Shakira: Wasn't too complicated. I went back to my UML class and sequence diagrams, like you suggested, and got rough counts for DIT, RFC, and LCOM. I couldn't find the CRC model, so I didn't count CBO. Jamie (smiling): You couldn't find the CRC model because I had it. Shakira: That's what I love about this team, superb communication. Vinod: I did my counts . . . did you guys develop numbers for the CK metrics? 86
(Jamie and Ed nod in the affirmative.) Jamie: Since I had the CRC cards, I took a look at CBO, and it looked pretty uniform across most of the classes. There was one exception, which I noted. Ed: There are a few classes where RFC is pretty high, compared with the averages . . . maybe we should take a look at simplifying them. Jamie: Maybe yes, maybe no. I'm still concerned about time, and I don't want to fix stuff that isn't really broken. Vinod: I agree with that. Maybe we CS550 Intro. to SE Spring 2007 should look for classes that have bad numbers in at least two or more of the CK metrics. Kind of two strikes and you're modified. Shakira (looking over Ed's list of classes with high RFC): Look, see this class? It's got a high LCOM m well as a high RFC. Two strikes? Vinod: Yeah I think so . . . it'll be difficult to implement because of complexity and difficult to test for the same reason. Probably worth designing two separate classes to achieve the same behavior. Jamie: You think modifying it'll save us time? Vinod: Over the long haul, yes. 87 Requirements Gathering for WebApps (pg518519) The scene:
Doug Miller's office. The players: Doug Miller manager of the software engineering group; Vinod Raman a member of the SafeHome software engineering team; three marketing people. The conversation: Doug: Management has decided that we're going to build an ecommerce site to sell SafeHome. Vinod: Whoa, Doug! We have no time to do that ... we're swamped with product software work. CS550 Intro. to SE Spring 2007 Doug: I know, I know ... we're going to outsource the development to a company that specializes in constructing ecommerce sites. They tell us that they'll get it up and running in under one month ... lots of reusable components. Vinod: Hmmm. Okay ... then why am I here? Doug: To expedite things--they want us to take a pass at requirements gathering for the
site. I'd like you to meet with the various stakeholders to gather some insight into basic requirements. 88 Vinod (exasperated): Doug ... you're not hearing me ... we're maxed out timewise and this .... Doug (interrupting): Just give it one day of your time, Vinod. Meet with the marketing types and get them to spec the basic content, function, you know, the usual drill. Vinod (resigned): Okay, I'll give 'em a call and schedule something for tomorrow, but you're not making my life any easier. Doug (smiling): That's why you get the big bucks. CS550 Intro. to SE Spring 2007 Vinod: Right. (Vinod meets with three marketing people the following day.) Vinod: You were telling me about the user's objectives and background. Marketing person #1: Like I said, we want the user to be able to customize the entire SafeHome system, you know, pick sensors, control panels, features and functions, then get a "bill of
materials" automatically generated, get pricing, and then purchase the system via the Web site. 89 Marketing person #2: We assume that the user is a homeowner--not technical--so we need to guide him or her through the process step by step. Marketing person #3: I'm not technical, but I'm worried about the specialty stuff that we need to do in addition to the basic e-commerce stuff. Vinod (addressing #3): Meaning? Marketing person #3: The hard part is going to be guiding the user through the "customizing process" in a way that is simple and complete. The actual e-commerce CS550 Intro. to SE Spring 2007 stuff is pretty straightforward. Marketing person #1: We've got to provide an 800 number for people who don't want to do the customization themselves. Marketing person #3: I agree. Vinod: Okay, we're going to have to talk about exactly how you'd like to do the product customization as a presales activity, but let's hold on that for a moment. I have a few other fundamental questions. Vinod (looking at Marketing person #2): You said that you wanted to guide the users through the process. Any special approach? 90
Marketing person #2: I'd like to see a step-by-step process, with fill-in-the-blanks responses to basic requirements questions, pull down menus, that sort of thing. Each step is a window, and each window's data is validated before moving to the next step. Vinod: Have you checked that out with representative users? Marketing person #2: No, but I will. Vinod: One more thing ... how does a user find our site? Marketing person #1: We're working on an ad campaign that CS550 Intro. to SE Spring 2007 will paste www.SafeHomeAssured .com in magazine ads, targeted direct mail, context-sensitive ads that appear in search engines, and maybe even some TV and radio spots. Vinod: What I mean is ... they'll always enter through the home page. Marketing person #3: That's what we'd like. Vinod: Okay, now we've got to get to work. Let's explore the details of how you want to customize systems on-line. 91
Outsourcing Preliminaries (pg529) The scene: Doug Miller's office. The players: Doug Miller (manager of the SafeHome software engineering team) Sharon Woods an employee of eCommerceSystems, the outsourcing vendor for the SafeHome ecommerce Web site and manager of the Web engineering team that will be doing the work. The conversation: Doug: Good to finally meet with you, Sharon. We've certainly got some work to do over the next month or so. CS550 Intro. to SE Spring 2007 Sharon (smiling): We do, but you guys seem to have your act together. Vinod has already given us a draft specification for the site and has also defined most of the important content objects and site functionality. Doug: Good. What else do you need?
Sharon: The e-commerce functionality is easy. The thing that worries me is the front end ... the work required to have the user customize the product pre-purchase. 92 Doug: Vinod gave you the basic procedure, didn't he? Sharon: He did, but I'd like to validate it with some real users. We'll also need to contact your content developers to get proper descriptions for each sensor, pictures, pricing, interface/interconnection info, that sort of thing. Doug: Did Vinod have time to do a rough storyboard of the customization process for you? Sharon: He's working on it as we speak. Said he had to put out a fire on the product side. He CS550 Intro. to SE Spring 2007 knows it's critical .. said he'd email it to me tomorrow morning. Doug: Okay . . . look, I'd like to stay in the loop on this project. Can we establish some ground rules for oversight on our end. I don't want to get in your way, but.... Sharon: Not a problem, we like to keep our clients involved. Doug: I'll serve as liaison for this project. All communication will come through me or someone like
Vinod that I appoint. Since we're on a tight schedule, I'd like to establish a schedule that has 93 one-day granularity and talk or e-mail with you everyday about accomplishments, problems, etc. I know it's a lot, but that's what I think is appropriate. Sharon: That's okay. Doug (picking up a few pages of paper from his desktop and handing them to Sharon): I've written up a rough schedule with milestone dates ... what do you think? Sharon (after studying the schedule): Hmmm. I'm not sure this'll work for us. Let me work up CS550 Intro. to SE Spring 2007 an alternative and e-mail it to you later today. Doug: Sure. 94 Refining Use-Cases for WebApps (pg543-544) The scene: Analysis modeling is almost The players:
Doug Miller's office. Doug Miller (manager of the SafeHome software engineering group) Sharon Woods manager of the outsourcing vendor's Web engineering team for the SafeHome e-commerce Web site Sam Chen manager of the SafeHomeAssured.com customer support organization. The conversation: Doug: Glad to hear things are progressing well, Sharon. CS550 Intro. to SE Spring 2007 Analysis modeling is almost complete? Sharon (smiling): We're making progress. The only set of use-cases left to develop from the user hierarchy [Figure 18.1] is the customer service staff category. Doug (looking at Sam): And you have those now, Sam? Sam: I do. I've e-mailed them to you, Sharon, and cc'd you, Doug. Here's the hardcopy version. (He hands sheets of paper to Doug and Sharon.) 95
Sam: The way we look at it, we want to use the SafeHomeAssured.com Web site as a support tool when customers phone in an order. Our phone reps will complete all necessary forms, etc. and process the order for the customer. Doug: Why not just refer the customer to the Web site? Sam (smiling): You techies think that everyone is comfortable with the Web. They're not! Plenty of people still like the telephone, so we have to give them that option. CS550 Intro. to SE Spring 2007 But we don't want to build a separate order processing system when most of the pieces are already in place on the Web. Sharon: Makes sense. (All parties read the use-cases [an example follows]): Use-case: describe home layout [note that this differs from the use-case of the same name for new customer category] I will ask the customer (via the phone) to describe each room of the house and will enter room dimensions and other characteristics on one big form 96
designed specifically for customer support personnel. Once the house data are entered I can save the data under the customer's name or phone number. Sharon: Sam, you've been kind of terse in your preliminary usecase descriptions. I think we're going to need to flesh them out a bit. Doug (nodding): I agree. Sam (frowning): How so? Sharon: Well ... you mention "one big form designed specifically for customer support personnel." CS550 Intro. to SE Spring 2007 We're going to need more detail. Sam: What I meant was that we don't need to walk our reps through the process like you do for an on-line customer. One big form should do the trick. Sharon: Let's sketch out what the form should look like. The parties work to provide sufficient detail to allow Sharon's team to make effective use of the use-case. 97 Interface Design Review (pg569-570) The scene: The players:
Doug Miller's office. Doug Miller (manager of the SafeHome software engineering group) Vinod Raman a member of the SafeHome product software engineering team. The conversation: Doug: Vinod, have you and the team had a chance to review the SafeHomeAssured.com ecommerce interface prototype? Vinod: Yeah ... we all went through it from a technical point CS550 Intro. to SE Spring 2007 of view, and I have a bunch of notes. I e-mailed 'em to Sharon [manager of the Web engineering team for the outsourcing vendor for the SafeHome e-commerce Web site yesterday. Doug: You and Sharon can get together and discuss the small stuff ... give me a summary of the important issues. Vinod: Overall, they've done a good job, nothing ground breaking, but it's a typical ecommerce interface, decent aesthetics, reasonable layout. They've hit all the important functions.... 98
Doug (smiling ruefully): But? Vinod: Well, there are a few things.... Doug: Such as ... ? Vinod (showing Doug a sequence of storyboards for the interface prototype): Here's the major functions menu that's displayed on the home page: Learn about SafeHome Describe your home Get SafeHome component recommendations Purchase a SafeHome system Get technical support CS550 Intro. to SE Spring 2007 The problem isn't with these functions, they're all okay, but the level of abstraction isn't right. Doug: They're all major functions, aren't they? Vinod: They are, but here's the thing ... you can purchase a system by inputting a list of components. no real need to describe the house, if you don't want to. I'd suggest only four menu options on the home page: Learn about SafeHome Specify the SafeHome system you need Purchase a SafeHome system 99
Get technical support When you select specify the SafeHome system you need, you'll then have the following options: Select SafeHome components Get SafeHome component recommendations house. I think it's a bit more logical. Doug: I agree. Have you talked with Sharon about this Vinod: No, I want to discuss this with marketing first, and then I'll give her a call. If you're a knowledgeable user, you'll select components from a set of categorized pull-down menus for sensors, cameras, control panels, etc. If you need help, you'll ask for a recommendation and that will require that you describe your CS550 Intro. to SE Spring 2007 100 WebApp Testing (pg611) The scene: The players:
Doug Miller's office. Doug Miller (manager of the SafeHome software engineering group) Vinod Raman a member of the product software engineering team. The conversation: Doug: What do you think of the SafeHomeAssured.com ecommerce WebApp V0.0? Vinod: The outsourcing vendor's done a good job. Sharon [development manager for the CS550 Intro. to SE Spring 2007 vendor] tells me they're testing as we speak. Doug: I'd like you and the rest of the team to do a little informal testing on the e-commerce site. Vinod (grimacing): I thought we were going to hire a thirdparty testing company to validate the WebApp. We're still killing ourselves trying to get the product software out the door. Doug: We're going to hire a testing vendor for performance and security testing, and our outsourcing vendor is already testing. Just thought another 101 point of view would be helpful,
and besides, we'd like to keep costs in line, so .. . Vinod (sighs): What are you looking for? Doug: I want to be sure that the interface and all navigation are solid. Vinod: I suppose we can start with the use-cases for each of the major interface functions: Learn about SafeHome Specify the SafeHome system you need Purchase a SafeHome system Get technical support CS550 Intro. to SE Spring 2007 Doug: Good. But take the navigation paths all the way to their conclusion. Vinod (looking through a notebook of use-cases): Yeah, when you select Specify the SafeHome system you need, that'll take you to: Select SafeHome components Get SafeHome component recommendations We can exercise the semantics of each path. Doug: While you're there, check out the content that appears at each navigation node.
102 Vinod: Of course . . . and the functional elements as well. Who's testing usability? Doug: Oh the testing vendor will coordinate usability testing. We've hired a market research firm to line up 20 typical users for the usability study, but if you guys uncover any usability issues .. Vinod: I know, pass them along. Doug: Thanks, Vinod. CS550 Intro. to SE Spring 2007 103 Team Structure (pg638) The scene: Doug Miller's office prior to the initiation of the SafeHome software project. The players:
Doug Miller (manager of the SafeHome software engineering team) Vinod Raman, Jamie Lazar, other members of the product software engineering team. The conversation: Doug: Have you guys had a chance to look over the preliminary info on SafeHome that marketing's prepared? CS550 Intro. to SE Spring 2007 Vinod (nodding and looking at his teammates): Yes. But we have a bunch of questions. Doug: Let's hold on that for a moment. I'd like to talk about how we're going to structure the team, who's responsible for what. ... Jamie: I'm really into the agile philosophy, Doug. I think we should be a self-organizing team. Vinod: I agree. Given the tight time line and some of the uncertainty, and that fact that we're all really competent [laughs], that seems like the right way to go. 104 Doug: That's okay with me, but you guys know the drill. Jamie (smiling and talking as if she were reciting something): We make tactical
decisions, about who does what and when, but it's our responsibility to get product out the door on time. Vinod: and with quality. Doug: Exactly. But remember there are constraints. Marketing defines the software increments to be produced--in consultation with us, of course. Jamie: And? CS550 Intro. to SE Spring 2007 Doug: And, we're going to use UML as our modeling approach. Vinod: But keep extraneous documentation to an absolute minimum. Doug: Who is the liaison with me? Jamie: We decided that Vinod will be the tech leadhe's got the most experience, so Vinod is your liaison, but feel free to talk to any of us. Doug (laughing): Don't worry, I will. 105 Establishing a Metrics Approach (pg653-654) Vinod (frowning): We've never The scene:
The players: Doug Miller's office as the SafeHome software project is about to begin. Doug Miller (manager of the SafeHome software engineering team) Vinod Raman, Jamie Lazar members of the product software engineering team. The conversation: Doug: Before we start work on this project, I'd like you guys to define and collect a set of simple metrics. To start, you'll have to define your goals. CS550 Intro. to SE Spring 2007 done that before, and ... Jamie (interrupting): And based on the timeline management has been talking about, we'll never have the time. What good are metrics anyway? Doug (raising his hand to stop the onslaught): Slow down and take a breath, guys. The fact that we've never done it before is all the more reason to start now, and the metrics work I'm talking about shouldn't take much time at all ... in fact, it just might save us time. Vinod: How? 106
Doug: Look, we're going to be doing a lot more in-house software engineering as our products get more intelligent, become Web enabled, all that ... and we need to understand the process we use to build software ... and improve it so we can build software better. The only way to do that is to measure. Jamie: But we're under time pressure, Doug. I'm not in favor of more paper pushing ... we need the time to do our work, not collect data. CS550 Intro. to SE Spring 2007 Doug (calmly): Jamie, an engineer's work involves collecting data, evaluating it, and using the results to improve the product and the process. Am I wrong? Jamie: No, but ... Doug: What if we hold the number of measures we collect to no more than five or six and focus on quality? Vinod: No one can argue against high quality ... Jamie: True ... but, I don't know, I still think this isn't necessary. 107
Doug: I'm going to ask you to humor me on this one. How much do you guys know about software metrics? Jamie (looking at Vinod): Not much. Doug: Here are some Web refs ... spend a few hours getting up to speed. Jamie (smiling): I thought you said this wouldn't take any time. Doug: Time you spend learning is never wasted ... go do it and then we'll establish some goals, ask a few questions, and define the metrics we need to collect. CS550 Intro. to SE Spring 2007 108 Establishing a Metrics Approach (pg664) Doug: It's always a good idea to The scene: The players: Doug Miller's office two days after initial meeting on software metrics. Doug Miller (manager of the SafeHome software engineering team) Vinod Raman, Jamie Lazar members of the product software engineering team.
The conversation: Doug: You both had a chance to learn a little about process and project metrics? Vinod and Jamie: [Both nod] CS550 Intro. to SE Spring 2007 establish goals when you adopt any metrics. What are yours? Vinod: Our metrics should focus on quality. In fact, our overall goal is to keep the number of errors we pass on from one software engineering activity to the next to an absolute minimum. Doug: And be very sure you keep the number of defects released with the product to as close to zero as possible. Vinod (nodding): Of course. Jamie: I like DRE as a metric, and 109 I think we can use it for the entire project. Also, we can use it as we move from one framework activity to the next. It'll encourage us to find errors at each step. Vinod: I'd also like to collect the number of hours we spend on reviews. Jamie: And the overall effort we spend on each software
engineering task. Doug: You can compute a reviewto-development ratio ... might be interesting. Jamie: I'd like to track some usecase data as well. Like the CS550 Intro. to SE Spring 2007 amount of effort required to develop a use-case, the amount of effort required to build software to implement a usecase, and ... Doug (smiling): I thought we were going to keep this simple. Vinod: We should, but once you get into this metrics stuff, there's a lot of interesting things to look at. Doug: I agree, but let's walk before we run, and stick to our goal. Limit data to be collected to five or six items, and we're ready to go. 110 Estimating (pg 685) The scene: The players: Doug Miller's office as project planning begins. Doug Miller (manager of the SafeHome
software engineering team) Vinod Raman, Jamie Lazar, other members of the product software engineering team. The conversation: Doug: We need to develop an effort estimate for the project, and then we've got to define a micro-schedule for the first increment and a macro schedule CS550 Intro. to SE Spring 2007 for the remaining increments. Vinod (nodding): Okay, but we haven't defined any increments yet. Doug: True, but that's why we need to estimate. Jamie (frowning): You want to know how long it's going to take us? Doug: Here's what I need. First, we need to functionally decompose the SafeHome software ... at a high level ... then we've got to estimate the number of lines of code that each function will take ... then .... 111 Jamie: Whoa! How are we supposed to do that? Vinod: I've done it on past projects. You use use-cases, determine the functionality required to implement each,
guesstimate the LOC count for each piece of the function. The best approach is to have everyone do it independently and then compare results. Doug: Or you can do a functional decomposition for the entire project. Jamie: But that'll take forever, and we've got to get started. CS550 Intro. to SE Spring 2007 Vinod: No ... it can be done in a few hours ... this morning, in fact. Doug: I agree ... we can't expect exactitude, just a ballpark idea of what the size of SafeHome will be. Jamie: I think we should just estimate effort ... that's all. Doug: We'll do that too. Then use both estimates as a cross check. Vinod: Let's go do it.... 112 Outsourcing (pg 701) The scene:
Meeting room at CPI Corporation. The players: Mal Golden senior manager, product development; Lee Warren engineering manager; Joe Camalleri executive VP, business development; Doug Miller project manager, software engineering. The conversation: Joe: We're considering outsourcing the SafeHome software engineering portion of the product. CS550 Intro. to SE Spring 2007 Doug (shocked): When did this happen? Lee: We got a quote from an offshore developer. It comes in at 30 percent below what your group seems to believe it will cost. Here. [Hands the quote to Doug who reads it.] Mal: As you know, Doug, we're trying to keep costs down, and 30 percent is 30 percent. Besides, these people come highly recommended. Doug (taking a breath and trying to remain calm): You guys caught me by surprise here, but before 113
you make a final decision, a few comments? Joe (nodding): Sure, go ahead. Doug: We haven't worked with this outsourcing company before, right? Mal: Right, but .... Doug: And they note that any changes to spec will be billed at an additional rate, right? Joe (frowning): True, but we expect that things will be reasonably stable. Doug: A bad assumption, Joe. Joe: Well, .... CS550 Intro. to SE Spring 2007 Doug: It's likely that we'll release new versions of this product over the next few years. And it's reasonable to assume that software will provide many of the new features, right? [All nod.] Doug: Have we ever coordinated an international project before? Lee (looking concerned): No, but I'm told .... Doug (trying to suppress his anger): So what you're telling me is: (1) we're about to work with an unknown vendor, (2) the costs to do this are not as low as they 114
seem, (3) we're de facto committing to work with them over many product releases, no matter what they do on the first one, and (4) we're going to learn on-the-job relative to an international project. [All remain silent.] Doug: Guys ... I think this is a mistake, and I'd like you to take a day to reconsider. We'll have far more control if we do the work in house. We have the expertise, and I can guarantee that it won't cost us much more ... the risk will be lower, and I know you're all CS550 Intro. to SE Spring 2007 risk averse, as I am. Joe (frowning): You've made a few good points, but you have a vested interest in keeping this project in-house. Doug: That's true, but it doesn't change the facts. Joe (with a sigh): Okay, let's table this for a day or two, give it some more thought, and meet again for a final decision. Doug, can I speak with you privately? Doug: Sure ... I really do want to be sure we do the right thing. 115 Tracking the Schedule (pg 721)
The scene: The players: Doug Miller's office, prior to the initiation of the SafeHome software project. Doug Miller (manager of the SafeHome software engineering team) Vinod Raman,Jamie Lazar, other members of the product software engineering team. The conversation: Doug (glancing at a Powerpoint slide): The schedule for the first SafeHome increment seems reasonable, but we're going to CS550 Intro. to SE Spring 2007 have trouble tracking progress. Vinod (a concerned look on his face): Why? We have tasks scheduled on a daily basis, plenty of work products, and we've been sure that we're not overallocating resources. Doug: All good, but how do we know when the analysis model for the first increment is complete? Jamie: Things are iterative, so that's difficult. Doug: I understand that, but ...
well, for instance, take analysis classes defined. You indicated that as a milestone. 116 Vinod: We have. Doug: Who makes that determination? Jamie (aggravated): They're done when they're done. Doug: That's not good enough, Jamie. We have to schedule FTRs [formal technical reviews, Chapter 26], and you haven't done that. The successful completion of a review on the analysis model, for instance, is a reasonable milestone. Understand? Jamie (frowning): Okay, back to the drawing board. CS550 Intro. to SE Spring 2007 Doug: It shouldn't take more than an hour to make the corrections ... everyone else can get started now. 117 Risk Analysis (pg 736) The scene:
The players: Doug Miller's office, prior to the initiation of the SafeHome software project. Doug Miller (manager of the SafeHome software engineering team) Vinod Raman, Jamie Lazar, other members of the product software engineering team. The conversation: Doug: I'd like to spend some time brainstorming risks for the SafeHome project. CS550 Intro. to SE Spring 2007 Jamie: As in what can go wrong? Doug: Yep. Here are a few categories where things can go wrong. [He shows everyone the categories noted in the introduction to Section 25.3.] Vinod: Umm ... do you want us to just call them out, Doug: No here's what I thought we'd do. Everyone make a list of risks ... right now ... (Ten minutes pass; everyone is writing.)
Doug: Okay, stop. Jamie: But I'm not done! 118 Doug: That's okay. We'll revisit the list again. Now, for each item on your list, assign a percent likelihood that the risk will occur. Then, assign an impact to the project on a scale of 1 (minor) to 5 (catastrophic). Vinod: So if I think that the risk is a coin flip, I specify a 50 percent likelihood, and if I think it'll have a moderate project impact, I specify a 3, right? Doug: Exactly. (Five minutes pass; everyone is writing.) CS550 Intro. to SE Spring 2007 Doug: Okay, stop. Now we'll make a group list on the white board. I'll do the writing, we'll call out one entry from your list in round robin format. (Fifteen minutes pass; the list is created.) Jamie (pointing at the board and laughing): Vinod, that risk (pointing toward an entry on the board) is ridiculous. There's a higher likelihood that we'll all get hit by lightning. We should remove it. 119
Doug: No, let's leave it for now. We consider all risks, no matter how weird. Later we'll winnow the list. Jamie: But we already have over 40 risks ... how on earth can we manage them all? Doug: We can't. That's why we'll define a cut-off after we sort these guys. I'll do that offline, and we'll meet again tomorrow. For now, get back to work ... and in your spare time, think about any risks that we've missed. CS550 Intro. to SE Spring 2007 120 SQA Issues (pg 758-759) The scene: The players: Doug Miller's office as the SafeHome software project begins. Doug Miller (manager of the SafeHome software engineering team) other members of the software engineering team.
The conversation: Doug: I know we didn't spend time developing an SQA plan for this project, but we're already into it and we have to consider quality ... right? Jamie: Sure. We've already decided that as we develop the CS550 Intro. to SE Spring 2007 requirements model [Chapters 7 and 8], Ed has committed to develop a V&V procedure for each requirement. Doug: That's really good, but we're not going to wait until testing to evaluate quality, are we? Vinod: No! Of course not. We've got reviews scheduled into the project plan for this software increment. We'll begin quality control with the reviews. Jamie: I'm a bit concerned that we won't have enough time to conduct all the reviews. In fact, I know we won't. 121 Doug: Hmmm. So what do you propose? Jamie: I say we select those elements of the analysis and design model that are most critical to
SafeHome and review them. Vinod: But what if we miss something in a part of the model we don't review? Shakira: I read something about a sampling technique [Section 26.4.4] that might help us target candidates for review. (Shakira explains the approach.) Jamie: Maybe ... but I'm not sure we even have time to sample every element of the models. CS550 Intro. to SE Spring 2007 Vinod: What do you want us to do, Doug? Doug: Let's steal something from Extreme Programming [Chapter 4]. We'll develop the elements of each model in pairs--two people--and conduct an informal review of each as we go. We'll then target "critical" elements for a more formal team review, but keep those reviews to a minimum. That way, everything gets looked at by more than one set of eyes, but we still maintain our delivery dates. Jamie: That means we're going to have to revise the schedule. Doug: So be it. Quality trumps schedule on this project. 122 SCM Issues (pg 786-787) The scene: The players:
Doug Miller's office as the SafeHome software project begins. Doug Miller (manager of the SafeHome software engineering team) Vinod Raman, Jamie Lazar, other members of the product software engineering team. The conversation: Doug: I know it's early, but we've got to talk about change management. Vinod (laughing): Hardly. Marketing called this morning CS550 Intro. to SE Spring 2007 with a few "second thoughts." Nothing major, but it's just the beginning. Jamie: We've been pretty informal about change management on past projects. Doug: I know, but this is bigger and more visible, and as I recall ... Vinod (nodding): We got killed by uncontrolled changes on the home lighting control project ... remember the delays that ... Doug (frowning): A nightmare that I'd prefer not to relive. Jamie: So what do we do. 123
Doug: As I see it, three things. First we have to develop--or borrow--a change control process. Jamie: You mean how people request changes? Vinod: Yeah, but also how we evaluate the change, decide when to do it (if that's what we decide), and how we keep records of what's affected by the change. Doug: Second, we've got to get a really good SCM tool for change and version control. Jamie: We can build a database CS550 Intro. to SE Spring 2007 for all of our work products. Vinod: They're called SCIs in this context, and most good tools provide some support for that. Doug: That's a good start, now we have to ... Jamie: Uh, Doug, you said there were three things Doug (smiling): Third--we've all got to commit to follow the change management process and use the tools--no matter what, okay? 124