EHR systems will typically utilize a range of different value sets to be used in different places of the system. Representing these value sets using the same terminology will support the comparison of data captured in different contexts. Additionally, using SNOMED CT to represent items value sets instead of locally defined terms enables effective management and overview of information, and helps to mitigate challenges related to redundancy and ambiguity.
Simple reference sets can be used to represent extensionally defined subsets of SNOMED CT components, whereas the query specification reference set are useful for representing the intensional definition of SNOMED CT subsets. In the query specification reference set, the expression constraints can be used to represent the query used for defining the set. This means that the query specification reference set can be used to manage the intensional definition of SNOMED CT subsets that function as value sets, which is illustrated below.
Figure 18.104.22.168-1: Query specification reference set used for generating value sets for different organisational units