Exchange structuresΒΆ
DDI Lifecycle instances are published and exchanged with one of two external wrappers, DDIInstance or FragmentInstance.
The DDIInstance provides a consistent top-level publication wrapper and in addition to some basic information about itself serves as the publication wrapper for four primary documenttypes: StudyUnit, Group, ResourcePackage, and LocalHoldingPackage.
The FragmentInstance is a uniform package used to transfer maintainable or versionable objects plus any associated Notes or OtherMaterial. These would be packets sent in response to system calls (external references, query calls, etc.).
DDI Instance:
The Citation, Coverage, OtherMaterial, DDIProfile, and TranslationInformation pertain to the DDI Instance as a whole. Note that the DDIInstance may be viewed as a temporary wrapper for publishing or transporting any of the major publication structures within DDI.
Fragment Instance:
The FragmentInstance is a wrapper for transporting a response to a request for a specific set of information. Although Maintainable, Versionable, and Identifiable objects may be referenced, the FragmentInstance can only transport a Maintainable or Versionable object.
If an Identifiable is the referenced object, its parent Versionable (or Maintainable) will be supplied. A FragmentInstance may contain any number of Versionable or Maintainable ojbects. The objects that are the specific responses to the request are listed in the TopLevelReference. For example, a single CodeList (Versionable object) may be requested and the FragmentInstance sent in response may contain the CodeList, the containing CodeListScheme, the referenced Categories, and the containing CategoryScheme. The requested CodeList would be noted in the TopLevelReference and the content of the returned objects would make up the Fragments.