Thoughts on possible MDC (Mapped Diagnostic Contexts) for core UIMA:
* the id of the CAS (if there is a cas in the context at the point of logging)
* the id of the pipeline (currently missing but could be architected into V3)
** within the pipeline, the key name of the component (if there is a cas in
the context at the point of logging)
** for UIMA-as/service: the client id information (which may include
pipeline id, "session id", etc.)
I'm guessing that more standard things like the caller's class, the thread
id/name, might be generally available.
-Marshall
