10 Principles of SOA

Here’s a very well written article on the principles of SOA:
http://www.infoq.com/articles/tilkov-10-soa-principles

To Summarize:

1. Explicit Boundaries
2. Shared Contract and Schema, not Class
3. Policy-driven
4. Autonomous
5. Wire formats, not Programming Language APIs
6. Document-oriented
7. Loosely coupled
8. Standards-compliant
9. Vendor independent
10. Metadata-driven