Original Paper Evaluating Structural Change in a Reference Terminology

Background: Clinical terminologies, like the domains they model, may change over time. Existing methods for identifying and characterizing terminology change, address individual concepts and their interrelationships rather than the overall structure of the terminology. Exposing high level terminology structure may improve developers ’ and users ’ ability to identify changes occurring over time. Objectives: To describe and demonstrate novel structural attributes for terminologies. Methods: We measured novel structural attributes of four successive versions of the National Drug File Reference Terminology Physiologic Effects hierarchy. Attributes included measures for overall size, dimension (ie, width, height, mass, depth), complexity (i.e., node recurrence, leafiness, branchiness) and balance (i.e., skew, variation, smoothness). Results: Among the four versions, the terminology size increased from 711 to 1638 concepts, increased in complexity, but did not improve in terms of symmetry. Conclusions: Visualizing and characterizing the structure of successive terminology versions revealed how the terminology changed at a high level, and where it may have been relatively over specified to meet modeling- or use-based needs