Clarify that format refers to mediaType

[philipashlock]

While many of the fieldnames are derived from DCAT it looks like format and mediaType were mixed up. The way that format is used here is really what mediaType is meant for (referring to IANA, aka MIME type). The distinction is described here: http://www.w3.org/TR/vocab-dcat/#Property:distribution_media_type

As a recommendation for a future iteration of the spec, format should be deprecated in favor of mediaType when referring to an IANA (aka MIME type) value as we're currently using it. The format field could still be acceptable for a more human readable name for the mediaType as per http://www.w3.org/TR/vocab-dcat/#Property:distribution_format

In related issues: mediaType should also be paired with downloadURL (#335) within the distribution array (#217)

[mhogeweg]

I want to connect a discussion to this issue that's been going on between a number of us offline (@ddnebert, @rsignell-usgs, @amilan17, ...) about format. There are some guidance documents such as the Geospatial Platform/data.gov Metadata Best Practices to Support data Discovery that suggest specific values of format that are not media types, or the Open Geospatial Consortium OGC Urn Policy that suggest specific values for service types (which in the end are referenced in the accessURL).

it would be good to get a consolidated list of formats (or mediaTypes as @philipashlock suggests) to be used in DCAT and through that hopefully upstream in agency catalogs and metadata practices.