Guidance on multiple metadata documents in different formats

[alexdutton]

It's currently unclear from the spec what happens if a client uploads multiple metadata documents using different metadata formats. Options include:

• maintain them alongside each other
• replace the previous metadata document that has a different format
• return a 409 Conflict response, to say that only one format is supported at the time

If more than one is supported at once, there should also be guidance on whether a SWORD service should attempt to reconcile between them.

[richard-jones]

Metadata formats are for deposit, but we should make it clear that there's no guarantee that the server will be able to expose the metadata in the same format that it's deposited. That is, the metadata format is for transmission, and what happens to it when it hits the server is not up to the client.

• add a section 19.3 to cover how alternative metadata formats are exposed in the Service Document

• Modify 18 to explain that metadata in does not strictly have to equate to metadata out

So to answer the specific points in the original issue: server should accept the metadata, extract the data it wants from them and store them how ever they are stored internally. The extracted metadata should update/replace/extend as needed any existing metadata in the internal "format". Servers are not beholden to reflect back metadata that is not the default SWORD format, so there's no requirement for them to manage all those other formats internally.

[richard-jones]

@alexsdutton probably one for the implementers guide here, too, about choices in managing additional formats.