Shahzad Bhatti

February 26, 2006

Software rewrites

Filed under: Computing — admin @ 10:58 am

Software rewrites
I just read a great Blog entry of Jim Shore about Software Rewrite. I like many have been in situation when I just wished that if we could redo, the application would have been much better. As some people say always do things twice
and throw away your first try. However, when you are working on a large
complicated software, despite the temptation it can be enormous effort.
According to Jim, If your platform or language does not change, dont’ throw
away your code instead refactor or redesign to work with existing software.
I have heard similar advince from Joel Spolsky. I have been involved with a few
projects with complete rewrites. In early 90s, there was widespread use of
the term “Re-engineering”, that related with business re-engineering and
encompassed a lot of rewrites of software. Later, I was involved with an
ITS project for Illinois Department of Transportation, where we rewrote old
CTIC project, which was written in C/UNIX and wrote new system
GCM Travel in C++/Java/CORBA. It
turned out to be major effort and over budget and years late. Unlike
private company, the government had plenty of tax dollars to keep spending
on the project. When I was at United, I worked on prettty badly written
software and I had to decide whether to continue with the software or rewrite.
I opted for incremental refactoring because unlike CTIC project, I had to
not only write new version, but had to maintain old software. It is terribly
risky strategy to maintain two versions of software. Martin Fowler also has
Strangler
Pattern
he describes for rewriting software. Unfortunately, I am
currently involved with another grand rewrite project (it was started
before I joined). It also has requirement to maintain two different
versions of the software and I can see a lot of time will be spend on
integrating two different versions. I have already seen people taking
short cuts to finish the project and before you would know it, it is
going to follow same road that previous project did.

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