Using UIMA Ruta: How do I annotate the first token of a text and use that annotation further? - uima

Question

I would like to annotate the first token of a text and use that annotation in following rules. I have tried different patterns:
Token.begin == 0 (doesn't work, although there definitely is a token that begins at 0)
Token{STARTSWITH(DocumentMetaData)}; (also doesn't work)
The only pattern that works is:
Document{->MARKFIRST(First)};
But if I try to use that annotation e.g. in the following way:
First{->MARK(FirstAgain)};
it doesn't work again. This makes absolutely no sense to me. There seems to be a really weird behaviour with annotations that start at 0.

Answer 1

This trivial task can be a bit tricky indeed, mainly because of the visibility settings. I do not know why your rules in the question do not work without having a look at the text that should be processed.
As for UIMA Ruta 2.7.0, I prefer a rule like:
# Token{->First};
Here some additional thoughts about the rules in the question:
Token.begin == 0;
Normally, there is not token with begin at 0 since the document starts with some whitespaces or line breaks. If there is actually a token that starts at offset 0 and the rule does not match, then something invisible is covering the begin of the end of the token. This depends of course of the filtering settings, but in case that you did not change them, it could be a bom.
Token{STARTSWITH(DocumentMetaData)};
Here, either the problem above applies, or the begin offset is not identical. If the DocumentMetaData covers the complete document, then I would bet on the leading whitespaces. Another reason could be that the internal indexing is broken, e.g., the tokens or the DocumentMetaData are created by an external analysis engine which was called with EXEC and no reindexing was configured in the action. This situation could also occur with unfortunate optimizations using the config params.
Document{->MARKFIRST(First)};
First{->MARK(FirstAgain)};
MARKFIRST creates an annotation using the offset of the first RutaBasic in the matched context IIRC. If the document starts with something invisible, e.g., a line break, then the second rule cannot match.
As a general advice in situations like this when some obvious simple rules do not work correctly as expected, I recommend adding some additional rules and using the debugging config with the explanation view. As rule like Token; can directly highlight if the visibility setting are problematic for the given tokens.
DISCLAIMER: I am a developer of UIMA Ruta