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Lexical Systems & Tools
LHNCBC's Lexical Systems Group develops and maintains the SPECIALIST lexicon and the tools that support and exploit it. The SPECIALIST Lexicon and NLP Tools are at the center of NLM's natural language research, providing a foundation for all our natural language processing efforts. In general, we investigate the contributions that natural language processing techniques can make to the task of mediating between the language of users and the language of online biomedical information resources. The SPECIALIST NLP Tools facilitate natural language processing by helping application developers with lexical variation and text analysis tasks in the biomedical domain.
Recently, the Lexical Systems Group began a project to enhance the derivational-variants function of the lexical tools. The derivational-variants function uses a set of derivational facts and rules to generate or identify derivational variants of input terms. Derivational variants are words related by a word-formation process like suffixation, prefixation or conversion (change of category). The current derivational variant system has only suffix rules and facts. These rules and facts are hand entered and curated. In order to add suffixation and conversion functionality to the system, the PDM team has developed a method to automatically extract candidate pairs of words that may be derivationally related, which helps automate the creation of rules and facts for suffixation and conversion.
The SPECIALIST Lexicon and Lexical tools are open source and freely downloadable. The 2012 release of the SPECIALIST Lexicon will contain over 462,000 records, representing over 830,000 forms, an increase of over 13,000 records from the 2011 release. Many of the new terms are derived from de-identified clinical records from our own De-identification project and from the MIMIC database.