Li Zhang, Yehoshua Perl, Michael Halper, James Geller, James J. Cimino. Enriching the Structure of the UMLS Semantic Network. In the proceding of the 2002 AMIA Conference

Abstract: The Unified Medical Language System (UMLS) Semantic Network (SN) onsisting of a network of semantic typesas a two-tree structure, where each semantic type has at most one parent semantic type. This arrangement is restrictive because some semantic types are, by their definition, specializations of several parents. As a proposed enhancement to the SN, its semantic types have previously been partitioned into groups, each of which contains semantic types of some specific area. However, some groups of this proposed partition contain forest (i.e., multiple-tree) structures or even isolated semantic types. Both situations imply a disconnected internal structure. Connectivity is actually one way to assess the proposed emantic validity? principle for partitions. It is a desired, although not required, property. In this paper, we introduce a methodology for identifying issing? IS-A links and adding them to the SN. This process transforms the SN into a Directed Acyclic Graph (DAG) structure, with semantic types permitted to have multiple parents. A result of our methodology is the transformation of the proposed SN partition into groups satisfying the connectivity property.