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Re: [dxwg] Question on IETF definition of Profile (#1002)

From: Ruben Verborgh via GitHub <sysbot+gh@w3.org>
Date: Wed, 17 Jul 2019 07:25:07 +0000
To: public-dxwg-wg@w3.org
Message-ID: <issue_comment.created-512136552-1563348306-sysbot+gh@w3.org>
> @smrgeoinfo suggested that
> 
> > this IETF definition is that it defines 'profile' to only apply to profiles of MIME types-- certainly a narrower scope that our discussions here.
> 
> @RubenVerborgh refuted that

Indeed. The definition says that profiles provide constraints in addition to those provided by more generic MIME types. For example, there could be a profile saying "use FOAF to represent people" and that profile could apply to text/turtle, application/ld+json, etc. Furthermore, there is nothing that says that profiles could not work together, and thus constrain each other. So there is a flexible relationship between profiles and MIME types; this definition just separates one from the other (which is not the case of some of the other proposed profile definitions).

> Does this part include or exclude the JSON-LD profiles that are different from our profiles

An IETF profile can be a JSON-LD profile; we don't see any reason to restrict it.
But the DXWG definition can be stricter than the IETF definition, so not a problem.

(I do have a [problem](https://github.com/w3c/dxwg/issues/976#issuecomment-512134251) with the exclusion of JSON-LD profiles, to the point I will be making below.)

> Can you give examples of "structural contraints that wouldn't be semantic constraints nor syntactical constraint?

Also see earlier thinking on https://ruben.verborgh.org/articles/fine-grained-content-negotiation/#where-mime-types-fall-short

The difference between structure and syntax is not black and white, but where I draw the line is "would I need a different parser?". For instance, a JSON document for which specific keys are required, would likely still be parsed with a JSON parser, not with a custom one. Hence, I see JSON as a MIME type, and the requirement of specific keys as a profile.

- Structure examples:
  - arrays can only contain numbers
  - objects can be nested up to 2 levels deep
  - only certain keys are allowed in certain places
- Semantic examples:
  - the value under the key "prev" has the interpretation of a back link
  - the value under the key "pages" indicates the total number of pages

> Maybe a reference to a definition for "structural" would help here.

Constraints about what constitutes a valid (not "meaningful") document that are not covered by the parser corresponding to the MIME type.

-- 
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Received on Wednesday, 17 July 2019 07:25:09 UTC

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