Step 2: Analysis & Estimation
Step 2: Build a schedule. Most students have never had to do this, so for some, it’s the most valuable part of the course. In order to explain how to go about it, I need to describe two important roles in real software projects: the product manager, and the project manager.
The product manager is the person who owns the spec. Typically, while developers are building Version N, she is talking to customers in order to find out what should go into Version N+1. She never, never asks them what features they want, because if she does, what she’ll get is a mish-mash of conversations overheard in frequent flyer lounges, and buzzwords plucked from the lead paragraphs of “Wired” articles.
Instead, she asks, “What can’t you do right now that you want to?”, “What do you find irritating in the current product?”, and, “Why are you buying our competitor’s software instead of ours?” She then translates the answers into a list of features to be considered for Version N+1.
(Note 1: the product manager usually also talks to developers to find out what they don’t like about the current software, and adds their wishes to the pile. Typically, these are things like “refactor the persistence layer”, “clean up the build”, and “upgrade to the latest version of Java”.)
So, it’s Monday morning. Version N shipped last Thursday (note 2: never, never ship on Friday); the team has had a weekend to catch its collective breath, and is ready to start work once again. (Note 3: if people are so burned out from the previous round that they need a whole week to recover, go and read Evan Robinson’s excellent article Why Crunch Mode Doesn’t Work: 6 Lessons.) At this point, the product manager divides up the list of desired features, and assigns them to the developers. Each developer then has some time—typically a few days to a couple of weeks—to do a little research, write some throwaway prototype code, and most importantly think. How could this feature be implemented? Is there a quick-and-dirty alternative that would take a tenth the time, but only deliver half of what was asked for? What impact will each alternative have on the build? On deployment? Will the feature be testable? And so on.
The outcome of this process is an analysis & estimation document, typically referred to as an “A&E”. There’s no set form for them, but usually, they include some background information (i.e., what the developer didn’t know before doing her research that she needed to learn in order to answer the question), a discussion of the alternatives, lessons learned from any prototyping that was done, and most importantly, an estimate of how much time would be needed to build each alternative. This time includes estimates from QA (for testing), the technical writer (for documenting), the people responsible for the build and creating the installer, and so on.
It’s Monday morning again. Three weeks have gone by, and all the A&E’s are done. When the time estimates are totalled, they come to 700 developer-days. Unfortunately, there are only 240 available: the size of the team is fixed, and the next release has to be available in May. This is normal. There is never enough time to add everything that everyone wants to a piece of software, and even if there was, it probably shouldn’t be done anyway.
So what do you do? The answer is, you find a large whiteboard and draw a 3x3 grid on it. The X axis is labeled “effort”; the Y axis, “importance”, and each is divided into “high”, “medium”, and “low”. (Note 4: finer-grained divisions, such as a 1-10 scale, are pointless, as they just encourage arguments over whether something is a 6 or a 7.)
Now, write each feature’s name on a yellow sticky note, and put it on the grid. (Or, if you don’t mind the smell of felt pens, write each feature’s number in the appropriate grid cell.) You should wind up with something like this:
You can probably guess what happens next. First, we throw away the high-effort, low-importance items in the bottom-right three cells. Next, we start assembling the other items into a schedule, starting with the upper-left corner. These are the things that will give the highest return on invested time; more importantly, starting with these means that if something goes wrong (and something always goes wrong), the team still has a good chance of having delivered something by the project’s end.
The items on the diagonal are the ones that have to be argued over. Should the team teackle Feature 14 (high effort, high importance), or Features 18-22 (lower importance, but less total effort)? It can take several sessions to sort this out; the most important thing is that management doesn’t shave the developers’ estimates in order to make things fit. If they do, then developers will start padding their estimates, which means management will shave even more, and the whole exercise becomes science fiction.
The team now has a schedule. For the rest of the development cycle, it belongs to the project manager. Her job is to make sure everyone is doing what they’re supposed to be doing, to handle interruptions (there are always interruptions), and most importantly, to track the team’s progress. After a few weeks, the project manager should compare how much has actually been done with how much was supposed to be done, and adjust the schedule accordingly. This does not mean, “Ask team members to start working nights and weekends.” (If you don’t know why, go and read Why Crunch Mode Doesn’t Work: 6 Lessons, and yes, it’s worth citing twice.) Instead, it means dropping some low-importance or high-effort features from the schedule, or replacing a full implementation with an easier-but-incomplete alternative. The product and project manager negotiate these issues as they arise, since they’re the two people who own the 3x3 grid’s axes.
Believe it or not, your customers will actually thank you for doing this, provided you do it early. “I’m sorry, we’re not going to have the frobnosticator for May 1” is OK on October 1, or even January 1, since it gives whoever was counting on the frobnosticator time to make other plans. It is not OK on April 30; neither is saying (or worse, not saying) that it’s “done”, but full of bugs.
(Which brings us to a pet peeve. Engineering project management textbooks often say that there’s a tradeoff between schedule, resources, and features: if you fix the number of people working on something, and what features they’re to produce, that determines the schedule, and so on. Some people in the software industry claim that it’s actually a four-way tradeoff, with “quality” as the fourth attribute. That’s dreck: if a feature only works half the time, it isn’t done (or it’s only 50% done), so treating quality as an independent dimension is bafflegab.)
Back to CSC49X. The schedule is fixed at 13 weeks (minus 3 for warmup, writing the final report, etc.), and team members are only supposed to put in approximately eight hours a week each. It’s still worth writing an A&E, though, since there are still features to be prioritized, work to be divided up, and schedule slippages to be recovered from. Some A&E’s from previous projects are up on the web to act as guidelines. When it’s your turn to write one, remember: the most important thing isn’t the document, it’s what you figure out about how to build your software while writing it.