Morpheme-based, cross-lingual indexing for medical document retrieval.

The increasing availability of machine-readable medical documents is not really matched with the sophistication of currently used retrieval facilities to deal with a variety of critical natural language phenomena. Still most popular are string-matching methods which encounter problems for the medical sublanguage, in particular, concerning the wide-spread use of complex word forms such as noun compounds. We introduce a methodology for the segmentation of complex compounds into medically motivated morphemes. Given the sublanguage patterns in our data these morphemes derive from German, Greek and Latin roots. For indexing and retrieval purposes, such a morpheme dictionary may be further structured by defining the semantic relations among morpheme sets in order to build up a multilingual morpheme thesaurus. We present a tool for thesaurus compilation and management, and outline a methodology for the proper construction and maintenance of a multilingual morpheme thesaurus.