Jeff Atwood blogged about a problem he is having with HTML sanitization on [StackOverflow](http://stackoverflow.com/ . The argument that Dare Obasanjo and Jon Galloway were trying to make to Jeff is that it doesn’t make sense to re-invent the wheel. People have solved this problem before and their code is available for re-use. Jeff’s argument is that he’s a professional developer and he should be able to solve this problem. He punctuates his argument with a quote from Richard Feynman, “what I cannot create, I do not understand.”
This is a fine argument if Jeff were a Nobel Prize winning Physicist working on the fundamental building blocks of the Universe. However, and I’m sad to report this, he isn’t. Software Development is not science. Some of us may use the scientific process for finding and fixing bugs, but at its heart software development is an engineering profession. What that means is that most of the hard problems have been solved before. Although it is important to understand how the solution works, it isn’t necessary to re-invent the wheel.
For example, given the inspiration and the need I could rewrite jQuery, but I don’t. Why? Because someone else who does have the time and inspiration already did it. More importantly, many thousands of people have already used it and reported enough bugs on it to make that library very stable and robust. The important part of this example though is that at any time I can, and have, opened it up and read through the code to make sure that it makes sense to me. I’m not proposing that Jeff use someone elses HTML scrubber blindly, I’m saying he should use someone elses HTML scrubber after reviewing it for himself to ensure that it meets his quality bar.
I also chose jQuery for this example because Jeff uses it extensively on Stack Overflow. He did not go out and write his own. In fact Jeff also uses the ASP.NET MVC framework, the ASP.NET framework, and the .NET Framework. All of these are software that he could have written given enough time and inspiration. At some point it comes down to ego. An HTML scrubber is a simple enough thing that he should be able to write it, but he really shouldn’t.