Topic: Estimating

Are You Building an Application or an Antique Web Framework?

Dietrich Kappe, Tuesday, May 5, 2009 @ 5:47 pm

photo credit: dave_7

A few years ago, a friend of mine asked me to help him estimating the conversion of a client/server application to the web. He came armed with a spreadsheet of features, I came armed with Ibuprofen and a red pen.

My usual approach to estimating involves breaking down the features into things that can be implemented by a pair of developers within a two week period. I give these a complexity factor of 1-5, then run them through an empirically derived formula to come up with an estimate in terms of person-iterations. (It's actually a little more complicated than that, but this is the main effort). Getting the count and size of these mini-features right is the key aspect of this technique. His spreadsheet had almost 300 features listed, and so we settled in for a day of fun.
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Software Development

Estimating Bugs and the Complex Behavior of Simple Systems

Dietrich Kappe, Monday, February 9, 2009 @ 2:01 pm

One of the bitter consolations of mathematical Computer Science is that we can demonstrate that applying algorithms to analyze algorithms is a largely fruitless task. It starts with the halting problem (can we write a program that takes a program as it's input and determines whether that program halts on all inputs) and goes on from there. The proof is by contradiction and -- like most "assume not" proofs -- is largely unsatisfying, i.e. it doesn't construct anything useful that you could apply to other problems. As Professor Herstein once told me in undergrad algebra, "Kappe: assume not assume not."

That's one of the theoretical underpinnings of why some software bugs are so hard to detect and fix; in a large system, automatically diagnosing bugs is akin to solving the halting problem. But what if we just try to solve this problem for a really small subset of programs? Well, first, it would have to be a really small subset. And second, even with very simple systems, answering questions about correctness, such as "does it halt," can be surprisingly difficult.

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Software Development