<p>**Description:**An ACT that organizes a set of component acts into a semantic grouping that have a shared subject. The subject may be either a subject participation (SBJ), subject act relationship (SUBJ), or child participation/act relationship types.</p><b>Discussion:</b>The focus in a CLUSTER act is the grouping of the contained acts. For example "a request to cluster" (RQO), "a type of cluster that is allowed to occur" (DEF), etc.<b>Examples:</b><p>* Radiologic investigations that might include administration of a dye, followed by radiographic observations; * "Isolate cluster" which includes all testing and specimen processing performed on a specific isolate; * a set of actions to perform at a particular stage in a clinical trial.</p>