A Semantic Navigation Tool for the UMLS

Background. The Knowledge Source Server (KSS) allows users to browse virtually every bit of information in the Unified Medical Language System (UMLS). In KSS, the presentation of contextual information from the Metathesaurus tends to reflect the organization of terms in the source vocabularies. For example, hierarchically related concepts are presented as lists of indented terms, one list for each vocabulary using this term. Instead of multiple trees, the semantic structure of the UMLS can be visualized as a graph in which concepts are the nodes and inter-concept relationships are the links between nodes. The graph structure offers a unified view of the context (Figure 1).