Monday, September 14, 2009

Agile Estimating and Planning

Agile Estimating and PlanningA few months ago my company picked up a new project with a fairly major government organization. The mission is to migrate several applications from a mainframe (Natural / Adabas) to a modern environment (C# / SQL Server). We were told that the mainframe was going to be disabled in about 9 months . . . period.

I told the client very early in the process that a typical waterfall approach would be impossible to implement under the conditions of the project and that we should take an agile methodology. The client agreed; however, the lack of resources corralled a few of our team members back to the waterfall approach. After a few weeks in waterfall, we realized that there was no way a waterfall project could be successful in this case.

We officially switched back to an agile approach and the project has been swimming along nicely ever since. I owe a lot of this success to Agile Estimating and Planning by Mike Cohn.

Agile Estimating and Planning is part of the Robert C. Martin Series and is listed in every "Top 10 Agile Books" lists I've found. The book is full of well thought out logical explanations and detailed examples of agile software development practices and principles. It is a very easy read (I read it in 2 days) and the author did an excellent job of relating each chapter to other chapters in the book.

The book begins by pointing out the difference between planning an agile project and agile planning. Next, Mike describes several reasons planning fails in many projects (some of which I discuss in my blog post a few weeks ago called "Programming is a Gas").

The next several chapters discuss the benefits and techniques of abstracting estimations away from time and monetary units. This creates a set of relative estimations based on feature complexity that allows the project room to change over time (and promotes more open and honest communication with the client). Two techniques discussed specifically are story points and ideal days.

The following section is more planning oriented with a detailed discussion of themes, features, and prioritization. There is a discussion about what to do with epics (very large stories) and boundaries on which to split those stories. Conversely, there is also a discussion about combining several small but related user stories into one larger more meaningful one.

The scheduling section describes release and iteration planning, estimating velocity, and techniques for buffering projects (especially risky projects). the tracking and communicating section gives you a set of methods for monitoring the release and iteration plans and a tool set you can use to communicate this with the project stakeholders.

The next section describes how (and why) agile projects work so well in real life. High visibility into the project, frequent feature based planning, and small story size make agile projects preferred for many software development groups as well as many clients who have had the good fortune to have experienced a well run agile project.

The final chapter is a hypothetical case study which demonstrates the entire agile software development life cycle from beginning to end. In this chapter, you get to see how an agile project begins, how stakeholders become involved, how iterations are planned, and how easily problems can be solved. If you read carefully, you can also pick up a lot of insight Mike has to offer from his experience as an agile coach.

You can purchase Agile Estimating and Planning from at a deeply discounted rate.

Thursday, September 3, 2009

Head First Design Patterns

Head First Design PatternsI read Head First Design Patterns about a year ago and it changed my life. Now, I know that a lot of non-programmers read this blog and I'm sure you must be thinking, "how can a book, especially one like that, possibly change your life?"

Well, it made my code much cleaner, much more flexible, and much easier to write. That's why I decided to make this the first book review on this blog. First of all, I'm a pretty big fan of the Head First style. I like most of the jokes and intentional thought provoking. It's a clever way to help people understand and remember what they're learning. Admittedly, sometimes it goes a little overboard, but I'd rather it go a little overboard than be a dry read. I read almost the whole book on a road trip from Atlanta to Orlando.

The book sets out to give the reader an understanding of what a design pattern is and what it's good for. A design pattern is a template for solving commonly occurring problems in software design. Head First Design Patterns discusses the details of about 15. You'll be surprised how many of these patterns you've seen before (and may have even written before). One of the big benefits you get out of this book is a common language to describe the patterns in your code. Next time you're doing a code review, you'll find yourself saying things like, "this is just a singleton" and your reviewer will understand what you're trying to accomplish without discussing the implementation details.

After reading this book, I've noticed more and more patterns:

The decorator pattern that you see throughout the .net framework. There are a lot of classes that take a stream and return a stream. Some read, some write, some encrypt — all of them are decorators.

The proxy pattern controls access to other objects. I wrote a blog post back in December of 2008 where I used the proxy pattern to write to multiple TextWriters.

The singleton pattern ensures that a class has only one instance and has a global point of access. It bears noting that there are a lot of programmers who have criticized the singleton to which the singleton replied in a public statement last year, "you can kiss my ass." It is true that the singleton can come back to bite you if you use it incorrectly; the singleton is the right tool for the job it has. Head First Design Patterns helps you understand what exactly that job is.

The template method pattern popped up the other day when I was looking at some PostSharp aspects. If you use the OnMethodInvocationAspect like I did with my memoizer, PostSharp will produce something very similar to a template method. Obviously, PostSharp isn't creating a base class and then overriding the template method, but it is allowing you to control the flow of the method without having knowledge of the method implementation.

The factory method and abstract factory patterns are also quite common and are well described in Head First Design Patterns. People use these patterns all the time. I've seen many data access layer implementations where a factory method loads a particular data access provider based on configuration options. You can achieve the same results with inversion of control containers like Ninject and autofac, but sometimes you just need a quick factory.

Almost every review I've seen of Head First Design Patterns has been positive; however, every once in a while you find a detractor like Jeff Atwood in his blog post from 2005. I think Jeff is probably a good guy and a good coder; he's just contrary and cynical. I know that being contrary and cynical doesn't negate your point, but it is a bit like crying wolf. I'm not going to address his argument in this post (because I could dedicate an entire post to the argument if I thought it'd do any good), but I think you should read it because he does have one some valid points.

Unneeded complexity is bad. I wouldn't say that design patterns should be eschewed altogether, but you should use the right pattern for the right problem. Reading this book should teach you to identify patterns yourself. What are some common problems you run into in your field? Can you think of a pattern for addressing these problems?

You have to learn to abstract your knowledge and apply it practically. Don't just decide that patterns are bad and start knocking books because the graphic on the cover has been reused. A pattern doesn't have to be necessary to be valuable. When the pattern provides maintainability, readability, testability, or simplicity then use the pattern; that's what it's there for. The pattern is just another tool in your tool belt.

I very seldom recommend you throw a specialized tool away just because you don't need it all the time. Buy (or borrow) Head First Design Patterns and focus on learning how to recognize and solve common problems. You won't regret it.

You can get Head First Design Patterns from for a great price.