oai4courts layer two is intended to be a "working" schema adequate to represent most caselaw metadata using OAI-PMH. The approaches taken will also be useful to other caselaw-metadata efforts (for example, metadata that is embedded in case files themselves). Its place in the overall plan for developing the oai4courts metadata standard is documented here.
As metadata standards for case law evolve, it will be necessary to identify certain entities, such as courts, in an unambiguous way. The simplest way to achive this is by adopting a standardized vocabulary.
URIs on the Semantic Web
The RDF / Semantic Web community has developed the concept of the URI as an identifier for non-document entities such as people and organizations. See, for example, Cool URIs for the Semantic Web.