Clinical decision support rules play a key role in the overall delivery of CDS. CDS rules typically follow a common pattern, which has been modeled in several healthcare standards formalisms. The Event-Condition-Action
model, as used in the HL7 community, is described below.
An informal representation or rule template which captures the Event-Condition-Action pattern is shown below. This pattern can be read as "ON event IF condition THEN action".
Event-Condition-Action rule template
Rules may reference both EHR data and reference data such as terminology to determine whether or not a specific condition is true. This topic will be explored in more detail in section 4. Inference Engine.