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. 2000 Jan-Feb;7(1):66-80.
doi: 10.1136/jamia.2000.0070066.

Representing the UMLS as an object-oriented database: modeling issues and advantages

H Gu  1 , Y Perl, J Geller, M Halper, L M Liu, J J Cimino
Affiliations

Representing the UMLS as an object-oriented database: modeling issues and advantages

H Gu et al. J Am Med Inform Assoc. 2000 Jan-Feb.

Abstract

Objective: The Unified Medical Language System (UMLS) combines many well-established authoritative medical informatics terminologies in one knowledge representation system. Such a resource is very valuable to the health care community and industry. However, the UMLS is very large and complex and poses serious comprehension problems for users and maintenance personnel. The authors present a representation to support the user's comprehension and navigation of the UMLS.

Design: An object-oriented database (OODB) representation is used to represent the two major components of the UMLS-the Metathesaurus and the Semantic Network-as a unified system. The semantic types of the Semantic Network are modeled as semantic type classes. Intersection classes are defined to model concepts of multiple semantic types, which are removed from the semantic type classes.

Results: The authors provide examples of how the intersection classes help expose omissions of concepts, highlight errors of semantic type classification, and uncover ambiguities of concepts in the UMLS. The resulting UMLS OODB schema is deeper and more refined than the Semantic Network, since intersection classes are introduced. The Metathesaurus is classified into more mutually exclusive, uniform sets of concepts. The schema improves the user's comprehension and navigation of the Metathesaurus.

Conclusions: The UMLS OODB schema supports the user's comprehension and navigation of the Metathesaurus. It also helps expose and resolve modeling problems in the UMLS.

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Figures

Figure 1
Figure 1
Extract from the Semantic Network. A semantic type is represented by a rounded-corner rectangle with its name written inside. An IS-A link is represented by a bold arrow directed from a semantic type to a parent semantic type.
Figure 2
Figure 2
A subschema of the OODB schema corresponding to ▶. A class is represented by a rectangle, and a subclass relationship is indicated by a bold arrow directed upward from the subclass to the superclass.
Figure 3
Figure 3
Six semantic types and the nine intersections among them.
Figure 4
Figure 4
Straighforward model of defining subclass relationships for the schema shown in ▶.
Figure 5
Figure 5
A subschema of the UMLS schema, obtained by use of the straightforward model.
Figure 6
Figure 6
Model of subclass relationships for the schema shown in ▶, obtained by use of the subclass definition rule.
Figure 7
Figure 7
Example of OODB modeling for a few semantic types.
Figure 8
Figure 8
A subschema of the UMLS schema, obtained by use of the subclass definition rule.
Figure 9
Figure 9
The subschema shown in ▶ after removal of redundant classifications.
Figure 10
Figure 10
The revised diagram of semantic types and intersections shown in ▶.
Figure 11
Figure 11
Comparison of the Metathesaurus traversal (left) and the combined traversal of the schema and instance layers (right). In the Metathesaurus traversal, the number of concepts at each level is shown in parentheses; the total number of scanned children was 467. In the combined traversal, the number of classes at each level is shown in parentheses, and the total number of scanned children was 48.
See this image and copyright information in PMC

References

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    1. Unified Medical Language System (UMLS). Bethesda, Md: National Library of Medicine, 1998.

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