Add basic sofa/view support

[jcklie]

• Annotations should be added to a CAS/sofa, instead of specifying sofa as a parameter.
• Allow getting sofas from a CAS
• Documentation

[jcklie]

@reckart What is the difference between a view and a sofa?

[reckart]

@rentier good question. A CAS may contain multiple SofAs - each representing one text or other piece of primary data which is being annotated. When interacting with a CAS, one usually interacts with a "view" of the CAS which has a single SofA and which indexes all annotations that annotate this SofA. Annotations are a subtype of "feature structures". The SofA itself is a "feature structure". Annotations can only be indexed in one view and are always bound to a SofA. I believe feature structures could in theory be indexed in multiple views and they are not bound to a particular SofA.

I recommend reading these papers:

• Design and implementation of the UIMA common analysis system
• An Effective, Java-Friendly Interface to the CAS

[jcklie]

Still needs documentation