At today's call, I took on an action to update the discovery service section to allow for discovery services that returned the data of interest rather than a reference to the data. Here is the updated material for your consideration:

Resource Discovery

Discovery services are vital to the data architecture. The data services may use the discovery services not just for registering services themselves, but also for registering the data sets that are stored by those services. This requires languages or ontologies for describing data. Discovery services may also register the locations of schema definitions. Discovery services may be built upon metadata repositories that contain information about other entities in the grid such as resources, and services. Some discovery services may return the name of the service and some may return an EPR to the service. Some discovery services may take a description of the desired data as input and return the data itself.

Allen