Archive entities and the `OverlapTable` delegate

Overlap tables are tables with rows that can exist either in the archive domain graph or either as part of reference data, but not both. Any attempt to create a table row that exists in both the archive domain graph and the reference data causes archiving to fail.

Entities that use overlap tables must implement the OverlapTable delegate. As these entities are both inside and outside the archive domain graph, they must also implement the Extractable delegate as well.

Specifying the `OverlapTable` delegate on entities

In PolicyCenter, the Document and Note tables are overlap tables. The following metadata definition of a data model extension to the Document entity type illustrates how to implement the OverlapTable delegate.

<implementsInterface iface="com.guidewire.pc.domain.document.impl.DocumentCoreExtMethods"
      impl="com.guidewire.pc.domain.document.impl.DocumentCoreExtMethodsImpl"/>
  ...
  <implementsEntity name="Extractable"/>
  <implementsEntity name="OverlapTable"/>
  ...
</internalExtension>

Specifying the `OverlapTable` attribute on edge foreign keys

In the base configuration, PolicyCenter does not implement the OverlapTable delegate through edge foreign keys. Guidewire recommends that you do not use edge foreign keys to implement the OverlapTable delegate.