compatibility issues of uimacpp vs. uimaj using uima-as

[Matthias Wendt]

Hello everybody,

to integrate a uimacpp AE with uimaj AEs, I have tried to deploy the 
uimacpp AE as a UIMA-AS service. During development some compatibility 
issues arose, which I think is worthwile commenting.

1. uimacpp does not support import by name <import name="..." />, which 
I think is not mentioned in the documentation.
2. using <import location="..." /> employs a different path resolving 
strategy from that of uimaj:
  -  both  support using absolute paths and relative paths (relative to 
the descriptor in which the import occurs)
  -  uimacpp can be given the environment variable UIMACPP_DATAPATH 
which is additionally used to resolve relative paths
  - However, uimaj does not support resolving relative <import 
location="..." /> from it's datapath.
3. I deployed the uimacpp AE service which has exactly the same 
typesystem as a uimaj AE in the pipeline. However, the CASes are 
incompatible with the following reason:
  - There is a type 'Constituent' which has a 'children' feature. 
'children' is of the range type 'FSArray' with the element type 
'Constituent'.
  - However, when getting the typesystem from the uimacpp service, the 
element type is ignored. Both components cannot be plugged into one 
pipeline, because of an exception complaining about incompatible 
typesystems.

I will work around the last issue by altering the typesystem (removing 
the element type), but this is not satisfactory.

Kind regards
Matthias