Having our cake and eating it too: how the GALEN Intermediate Representation reconciles internal complexity with users' requirements for appropriateness and simplicity.

Clinical terminologies are complex objects, getting more complex as the requirements on them grow, and as more complex technologies are used in their construction. But to the clinical end-user, functionality and utility is important, not inherent complexity--the simpler a clinical terminology can be for the end-user, the better. To reconcile these contradictory requirements, the GALEN Programme has developed an Intermediate Representation that allows the OpenGALEN Clinical Terminology to retain a high degree of internal complexity, whilst allowing it to be efficiently maintained, and easily used. This paper describes the elements of the Intermediate Representation, how it works, and some experience of its use.