Text type evaluation

Probabilistic taggers rely basically on similarities between training and application data.

It seems obvious that a tagger which is trained on a ``standard'' corpus will be less accurate on a text with highly irregular sentence structures (for example technical maintenance manuals, etc.). The question is, however, how big the structural (syntactic) differences are in the corpora used in ``real-life applications'', and how much these differences really influence the tagger accuracy.

We cannot provide a well defined measurement of text type difference and thus the experiments are based on a subjective choice of texts which we assume are different with respect to their syntactic structure.

The experiment consists in producing several ``specialised'' taggers, i.e. each tagger is trained on one specific text type only. The resulting taggers are then evaluated with test corpora which also correspond to different text types.

• Test:
  • Training on a given text type
  • Run the trained tagger on this same text type;
  • Run the trained tagger on another text type
• Second test setup:
  • Training on a mixture of two (supposedly quite different) text types;
  • Test on only one of the two text types taken in isolation (do so for either text type). Compare results.