W3C home > Mailing lists > Public > public-dxwg-wg@w3.org > March 2019

Re: [dxwg] prof:inheritedFrom needs more convincing case and/or example (#642)

From: Rob Atkinson via GitHub <sysbot+gh@w3.org>
Date: Thu, 21 Mar 2019 04:34:41 +0000
To: public-dxwg-wg@w3.org
Message-ID: <issue_comment.created-475110841-1553142880-sysbot+gh@w3.org>
@VladimirAlexiev 

q: what's the relation between dcat:Distribution and ResourceDescriptor and "artefact"?
a: the relation between dcat:Distribution and prof:ResourceDescriptor is a "non-normative alignment" via subclass - i.e. an implementer can safely choose this if they wish but use of dcat is not imposed.  The relationship between ResourceDescriptor and "artifact" is the same relationship as between Distribution and dcat:downloadURL

"I think a Distribution has only one URL and may have several format (if that URL supports conneg)"
- this cardinality is not defined in DCAT.  A case to constrain it is not clear, so cardinality is left open. Profiles of Profile and DCAT would be the appropriate mechanism to make such a constraint in an operational context.

* "If the purpose of ResourceDescriptor is to describe the relation of the artefact to the profile, then it makes sense to allow several artefacts under one ResourceDescriptor, differing only by format."
a: there is nothing to stop this approach. The semantics of the use of dct:format on the resource descriptor (or DCAT distribution) probably requires an entailment rule to be axiomitised - at this stage we do not have sufficient evidence or experience to enforce a particular pattern, but we do explicitly wish it to be easy to use DCAT to catalogue profiles

* "So maybe dcat:Distribution is equivalent to artefact?" 
a: no more so than dcat:Distribution is equivalent to the range of a dcat:accessURL - in simple cases they may be the same, but the option to provide additional metadata about the relation of the artefact to the profile is important. in general, having a descriptor for an object allows a cataloguing context to make statements about that object independent of any intrinsic properties - which will generally help in Linked Data environments to retrieve the metadata about the object indpendently of getting its entire contents. It is not impossible, but a much higher barrier, to demand , for example, that every PDF document supports canonical metadata form accessible via conneg from the same downloadURL.

This does get deep into the whole design of DCAT and the relationships between descriptors and content, and broader issues of lack of a canonical way to resolve a single URI to get metadata about an object from a particular viewpoint (different people may need to see different levels of detail).  Cataloguing is the default way to handle this problem, and we provide a minimal level of support for that architecture. (note this is all rather peripheral - as its description conformance hierarchies and roles that are the functional goals here)

-- 
GitHub Notification of comment by rob-metalinkage
Please view or discuss this issue at https://github.com/w3c/dxwg/issues/642#issuecomment-475110841 using your GitHub account
Received on Thursday, 21 March 2019 04:34:43 UTC

This archive was generated by hypermail 2.4.0 : Friday, 17 January 2020 19:42:15 UTC