<status value="active"/> <date value="2014-03-26"/> <description value="A group of entries within a composition, topic or category that have a logical association with one another. The representation of a single observation or action might itself be multi-part. The data might need to be represented as a nested set of values, as a table, list, or as a time series. The Cluster class permits such aggregation within an entry for such compound data. Examples include "Haematology investigations" which might include two or more distinct batteries. A cluster may contain batteries and/or individual entries"/> <immutable value="true"/> <compose> <include> <system value="http://terminology.hl7.org/CodeSystem/v3-ActClass"/> <filter> <property value="concept"/> <op value="is-a"/> <value value="CLUSTER"/> </filter> </include> </compose> </ValueSet>