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Real-world applications need to be configurable. There are lots of reasons an app must be configured - different environment, modify the thresholds, even change what providers are used for a task. There's a big difference between coding, and configuration:
Coding implies writing the actual logic in some language (C#, VB, Java, Html, JavaScript, CSS, Sql, etc...). Coding, by its nature, can deal with complex logic, and may reside in many files across many directories. Sometimes code needs to be compiled into binaries. There's a lot of room for error here, which is why IDEs (like Visual Studio) provide code debugging, and why the community encourages unit tests and code reviews.
Configuration implies using knowledge of the domain to tweak the app, after it's been deployed, usually via a small number of config files.
| Coding | Configuration | |
| Requires knowledge of language syntax | Yes (and usually for many languages) | No (syntax is usually just xml. A huge point of configs is that they abstract out syntax). |
| Requires business domain knowledge | Yes | Yes |
| Requires re-compiling | Sometimes (C#, Java --> Yes, Html/Sql --> No) | No. Usually just xml or plain text |
| Number of files | Many - a 10,000 line app, with 50 files, could still just have 1 app.config | Few (usually just 1, or 1 per directory) |
More and more, the push is to abstract coding into configuration. I believe WCF is big on this - instead of getting bogged down in how to transport data (web services, remoting, FTP, messaging, etc...) you just configure the app as appropriate. We also see this in domain specific languages and code generation. For example, .Net tiers has a big config file, but it makes perfect sense if you understand the concepts of N-Tier architecture. So, you can do a little configuration, and it generates 1000s of lines, which spares you from tons of tedious coding.
This is only true for small apps. Have you ever tried working with
SharePoint configuration files? Hundreds of xml files, typically thousands
of lines each, and while the syntax is "just xml", you still have to work
out just what sort of xml the application is expecting.
It does also open up a whole new market for configuration manager
applications as well. Just look at the WCF Configuration Editor in the
Windows SDK. OK, so WCF Configuration is all XML-based, but it's still way
easier to edit it in a tool.
Good points, thanks.
I do see a blurry line - for example is MSBuild still coding, or really
just a massive configuration script.
I wrote about configuration bloat a while ago:
http://harriyott.com/2005/03/programming-by-text-file.aspx
