I use a layered enterprise architecture representation below to provide a framework to capture the knowledge of tools and best practices that are required in builing an enterprise architecture defintion.
Web UI |
Client UI |
| Client UI Navigation / Validation Layer | |
Integration Layer |
|
External Systems |
|
| Business Layer |
Other common cross-layer architectural concerns:
- Security
- Exception Handling and Logging
- Internationalization
Core J2EE Patterns
Portal Development with Apache Tools 
Java Open Source Programming