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Re: Do we really need a notion of profile "conformance"?

From: Antoine Isaac <aisaac@few.vu.nl>
Date: Tue, 18 Jun 2019 21:35:18 +0200
To: <public-dxwg-wg@w3.org>
Message-ID: <b8243ea1-54e4-7d45-f369-733a9274ce42@few.vu.nl>
Hi Tom, all,

I believe that the group has already expressed its discomfort with the IETF definition, as it was considered when we had our (very long) discussion that has lead to the current definition DXWG [1] and was not kept. As much as I'm ok adapting this DXWG definition (and I may suggest it in a short while) I would rather want to avoid reviving the entire discussion. In particular I like very much the notion of 'specification' rather than 'document'.
'document' points to a rather concrete instance of a profile, while 'specification' is more conceptual, and allows to to group things together. For example, 'specification' allows me to consider the Europeana Data Model as a specification that can be detailed in an XML Schema, an RDFS/OWL document, or a SHACL represention. If we jump straight to the definition, then all the 'instanciations' of the Europeana Data Model would live in splendid isolation. There are many more downsides to focusing on 'documents' but this one seems a major showstopper to me.

DCAT mentions 'specification' too [2]. In fact I believe that if DCAT doesn't cite the DXWG definition but it's more close to it than the one of IETF. And I believe it's not far at all. But this requires a unifying approach to profiles, which I am trying to articulate (and have started to write) but which I'll probably fail to send before the call.
By the way DCAT does rely on a notion of conformance: "A data catalog that conforms to the profile also conforms to DCAT." And this is where it becomes closer to the DXWG, as it hints that profiles are chiefly based on "Additional constraints in a profile".
And of course the Profile Negotiation document has conformance in plenty places [3]. So we'll probably need to articulate something on this. I'll try to hook something in what I'm trying to write...



[1] https://www.w3.org/2017/dxwg/wiki/ProfileContext#Definitions_of_Profile.2C_Application_Profile.2C_Metadata_Application_Profile
[2] https://w3c.github.io/dxwg/dcat/#conformance
[3] https://w3c.github.io/dxwg/conneg-by-ap/
On 12/06/2019 09:46, Thomas Baker wrote:
> An XML, SHACL, or ShEx processor can test whether some
> data conforms to an XML schema or to a SHACL or ShEx
> document.
> However, I see no requirement simply to assert (for
> example, in metadata) that an XML schema, SHACL or ShEx
> document -- not to mention the PDF of an application
> profile -- "conforms to" some base specification.  The
> XML schema, SHACL or ShEx document, or even the PDF of an
> application profile usually cite their own sources --
> e.g., the namespaces used -- explicitly enough.
> In the absence of an algorithmic conformance test, simply
> asserting conformance only really states intent -- for
> example, that something conforms to the text of the
> two-page EU Regulation at
> https://eur-lex.europa.eu/eli/reg/2014/1312/oj) as per
> Section 12.2.1 of [3].  The result of an algorithmic
> conformance test can be recorded in metadata, though
> since most specifications are mutable, at least in
> principle, such an assertion can only reliably be seen as
> the result of a given test against a version of a
> document at a given time.
> For CONNEG, the generic definition of "profile" provided
> by Svensson and Verborgh -- "a document that expresses
> the structural and/or semantic constraints of other
> documents" [1] -- seems good enough if the typical use
> case will be to point to an application profile such as
> DCAT. The IETF draft reinforces this point by citing the
> definition of "application profile" from Heery and Patel
> 2000.
> To conclude:
> * For CONNEG, I see no need to define "profile" any more
>    precisely than Svensson and Verborgh [1].
> * As the section on DCAT conformance says very clearly,
>    DCAT APs are "application profiles" in the Dublin Core
>    sense: "The notion of profile used in this document
>    denotes metadata specifications that the Dublin Core
>    community would call application profiles" [2].
> I see no compelling need to harmonize the definition of
> "profile" between CONNEG and DCAT, and for the purposes
> of CONNEG and DCAT, I see no need for a more elaborate or
> generalized theory of profiles.  A WG Note on Guidance
> summarizing existing practice would be useful though I do
> not see it as being on the critical path to finalizing
> Tom
> [1] https://profilenegotiation.github.io/I-D-Accept--Schema/I-D-accept-schema
> [2] https://w3c.github.io/dxwg/dcat/#conformance
> [3] https://w3c.github.io/dxwg/dcat/#quality-conformance-statement
Received on Tuesday, 18 June 2019 19:35:45 UTC

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