Basic Worklist Information Models consist of a single level, that includes all Matching Key Attributes and all Return Key Attributes, which may be sent from the SCU to the SCP in the request and whose values are expected to be returned from the SCP to the SCU in each of the responses (or worklist items). The Matching Key Attribute values in the request specify the worklist items that are to be returned in the responses. All Key Attributes (the Matching Key Attributes and the Return Key Attributes) in the request determine which Attribute values are returned in the responses for that worklist.
A Worklist Item has a one-to-one relationship with the real-world object defining the root for the Basic Worklist Information Model. In addition the worklist item is related to a number of other objects from the real-world model. Each of these real-world objects is represented by a hierarchy of entities organized in an (internal) Entity-Relationship Model.