The components and criteria within a CDS rule should also be considered when designing or implementing the rules. Some of the additional aspects of these considerations have been described below.

Multi-Component CDS Rules

Multiple events, conditions, or actions may be associated with each CDS rule.  For example, two separate actions defined in a medication allergy rule might be:

1. Firstly to alert the user and;
2. Secondly to suggest an alternative drug

Additional examples of complex rules, with multiple conditions and actions, are provided in the section  3.1.3. Rule Examples.

Criteria in CDS Conditions

Each CDS condition can be further subdivided into one or more criterion, each consisting of a "name-value" pair. The criterion name will typically map to a data element in the electronic health record, while the criterion value is compared with the data that populates this element in the patient's health record.

Table 3.1.2-1: Examples of criterion name-value pairs

Criteria Values

Some criteria may refer to the value of coded data elements, while others may refer to the value of non-coded data elements. When a criterion refers to a SNOMED CT encoded data element, the value may be a SNOMED CT Expression Constraint that defines the permitted subset of concepts that will satisfy this criteria.

Table 3.1.2-2: Examples of criteria which refer to coded data elements

Criteria that refer to non-coded data elements may use operators that are valid for the given element's data type. For example, criterion that refer to numeric data elements may use standard mathematical operators to restrict the required value.

Table 3.1.2-3: Examples of non-coded data elements