add README.md, cqrs.ucls and etc/cqrs.urm.puml

cqrs/README.md

@@ -0,0 +1,29 @@
+---
+layout: pattern
+title: CQRS
+folder: cqrs
+permalink: /patterns/cqrs/
+pumlid: 
+categories: Architectural
+tags:
+ - Java
+ - Difficulty-Intermediate
+---
+
+## Intent
+CQRS Command Query Responsibility Segregation - Seperate the query side from the command side.
+
+![alt text](./etc/cqrs.png "CQRS")
+
+## Applicability
+Use the CQRS pattern when
+
+* you want to scale the queries and commands independently.
+* you want to use different data models for queries and commands. Useful when dealing with complex domains.
+* you want to use architectures like event sourcing or task based UI.
+
+## Credits
+
+* [Greg Young - CQRS, Task Based UIs, Event Sourcing agh!](http://www.amazon.com/Effective-Java-Edition-Joshua-Bloch/dp/0321356683)
+* [Martin Fowler - CQRS](http://codebetter.com/gregyoung/2010/02/16/cqrs-task-based-uis-event-sourcing-agh/)
+* [Oliver Wolf - CQRS for Great Good](https://www.youtube.com/watch?v=Ge53swja9Dw)