Please see:
http://en.wikipedia.org/wiki/Maintainability
To make it easier to maintain Tiki code:
- Code reuse from External Libraries (Zend Framework, jQuery, Smarty, etc.)
- Merge Files
- Merge features
- DevTips Coding standards, etc.
- Quality Team
- Code Review
- Campaign to Win
- changi's work
- Modularity
- Infrastructure Revamp