Specifies the Logical ID of the object used for external binding. A Logical ID identifies a class of objects, any one of which may be selected at any given time. For example, a Logical ID can identify a specific version of a specific CMS object (fixed reference) or the current version (floating reference). Logical IDs are valid across sessions, and are stored inside structured documents. At any time, you can translate a Logical ID into a POID that identifies a specific version of a specific object.