I want to incorporate DCAT-AP in our own standard for dataset metadata.
While the DCAT-AP specification does provide some reasonable requirements, I do have an issue with accessURL and downloadURL.
In our domain downloadURL points out files which can be downloaded directly, without having to follow some access procedure.
While accessURL provides a 'gate' to the desired source which can be acquired, if one adheres to the required access procedure.
This seems to be the understanding of the usage note of the DCAT specification as well:
"dcat:downloadURL is a specific form of dcat:accessURL. Nevertheless, DCAT does not define dcat:downloadURL as a sub-property of dcat:accessURL not to enforce this entailment as DCAT profiles may wish to impose a stronger separation where they only use accessURL for non-download locations."
Making accessURL mandatory to all distributions seems to clash with this understanding of downloadURL and accessURL. In our use case, in order to conform with DCAT-AP, we would have to provide an additional accessURL (on top of the downloadURL) which would contain either an alibi access location, or better, a duplicate of the downloadURL.
Also, our subclasses of dcat:Distribution which require a downloadURL, would have to be modified to demand an accessURL pointing to the exact resource as downloadURL. These consequences are probably not intended by the DCAT vocabulary.
In my view, the best solution would be to change this requirement to demand either an accessURL or a downloadURL for any dcat:Distribution.
I'm looking forward to your insights on this matter.