optional rule element does not match as expected

Question

I have a UIMA Ruta script:

W{REGEXP("A")}  W{REGEXP("B")}  W?{REGEXP("C")}  W{REGEXP("D")}

Which I designed so that it would match the following:

A B C D

A B D

However, it only matches the 1st pattern.

Why is the third rule element not behaving as an optional element?

Thanks, Dimitris.

Answer 1

This is a bug in UIMA Ruta 2.1.0, which was caused by the different evaluation of matching references and conditions. It's already fixed in the current trunk and will be available in the next release (approx. end of January). See UIMA 3338: https://issues.apache.org/jira/browse/UIMA-3338