EntryDescription is a subclass of OpaqueData. The purpose behind this is that there are certain textual fields that some CTS2 service implementations may want constrain. As an example, Designation text is of type \ EntryDescription, but implementations may want to restrict the OpaqueData value attribute to a simple string rather than xs:anyType. When OpaqueData appears directly as a model element, implementations must be able to support the full OpaqueData model. EntryDescription, however, may be constrained by implementations or specialized PSMs.