A user created a CAS but didn't set a Subject-of-Analysis. The CAS's type system has some types which are subtypes of Annotation; the user made one of those types.
Later, serialization / deserialization behaved strangely (because there was an Annotation instance, but no subject-of-analysis - something the framework probably never though of "supporting".). Should UIMA support this, or report an error if a user makes an Annotation with no subject of analysis? The suggested reason to support this was that the Annotation carried other information which was being used, and was wanted. A work-around which worked was to set an String of length 0 as the subject of analysis. The usual way these kinds of things have been decided is to "guess" if the more likely scenario is one of a user error, or a user intent. Here, the user seemed to intend this. If this was supported, there might be other unintended consequences - such as setting a subject-of-analysis **after** some Annotations were made. -Marshall
