Writing articles on Yii

I want to write an article or even a whole series on Yii (www.yiiframework.com), but here’s the problem — I can’t find a single topic that wouldn’t be covered in the manual, the tutorial on creating a blog, or a reference book on classes.

Please tell me which topics would be interesting for you?

Here are some ideas (the list will be updated):
- Working with modules, creating modular applications
- Events, event handling
- Behavior: what and how?
- Caching: data, fragments, the whole page. Dependencies Practical examples.
- Global states: what and how?
- Overview of key components
- Review of classes
- Links to ActiveRecord
- Rules for data models
- Multi-language support (i18n and l10n)
- Logging and profiling
- Extensions (extensions). Differences from modules.
- Validation and access control
- Filters: what and how?
- Web services
- Widgets: review existing, create new
- Beautiful URLs
- Security. Prevent sql-injection, xss, csrf.

If any one or several topics from this list interest you, indicate it in the comment. In this way I will know what is more relevant and what is less.