David Chappell paper : Introducing SCA

David Chappell has written a nice paper on SCA technology: Introducing SCA

The paper explains the concept of SCA and its attributes (components, composite, domains etc.). It includes samples of new SCA components. To learn SCA, this paper is a good starting point, which covers all the basics of this new technology.

The SCA specification defines:

1. A new programming model to create services. For example: creating EJB is a programming model, which the developer defines classes & configuration files following EJB standard. The EJB is deployed in an EJB container, and the ejb-attributes (security, transaction etc.) are defined in the deployment-configuration file. In similar way, SCA defines a new programming model to create classes and configuration files. These classes and configuration files are deployed on SCA runtime (Example: Tuscuny).
   
2. Composition of components: SCA specification a new method to create composite components. This is very much similar to orchestration. The orchestration is defined using BPEL like language. In this case, it is defined in the configuration file of SCA. One component gets reference to another component using inversion of control pattern. So, if one component composes of another, it is defined with annotation  "@Reference". The reference is defined in the configuration file. It is the responsibility of SCA runtime to create the object and make it available to the parent class using getter/setter.

However, it briefly touches some advanced (but important) aspects of any services. Well, this paper being the introduction, the advanced topics is out of scope for this papers. The topics, which I am referring, are:

1. Transaction Handling
2. Security Implementation
3. Development Tools
4. Runtime
5. Monitoring (SCA does not specify standard MBeans)

A new SCA transaction-policy specification (draft version) is published on 3rd December 2007 (Link: SCA Specifications). I have not reviewed it so far.