Multiple Metadata / Best Metadata Return

The OAI protocol currently supports a simple mapping of metadata names to metadata formats, whereby a metadata record can be requested for exactly one record in exactly one format in a single GetRecord request. In the case of ListRecords, all records within a set and/or date range may be requested but there is still the restriction of a single metadata format. This is usually sufficient for simple harvesting with the intention of transferring a stream of metadata records from the source archive to a service provider. However, in some cases, it may be desirable to obtain the most complete metadata format or a set of metadata formats for an identifier. In order to accomplish this it is currently necessary to submit multiple requests with different parameters and this is not most efficient.