The description for this class reads:
the JCas class model for the CAS type uima.cas.Annotation. It defines two integer valued features indicating the begin and end of the span being annotated. There is also a method to retrieve the spanned text as a string.
This is incorrect. It should definitely mention that your type must extend this class if it is to be SOFA specific. This is as opposed to extending TOP where your type will not remember which SOFA it was created in.