Page History

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Originally values sets for LexEVS were expressed in terms similar to the ISO 11179 specification. Value domains were conceived as a set of rules that could be applied to any version of a given terminology with the expectation that a current version of the value set would be expressed.   Eventually Value set domains, called value set definitions in LexGrid, were expressed a entries in an xml file. As this file set grew into the hundreds it became more difficult to keep up to date and more error prone.  Loading time from the files into LexEVS definition and coding scheme entires was extensive enough to be subject to network and other system performance problems.  Eventually the NCIt provided a framework of relations to define value sets in a more succinct set of rules.  This framework was eventually pointed to as a more viable method for defining value sets and it was suggested as an alternative source to a set of nearly a thousand xml files that represented the value set definitions.

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