PR#2 for Provenance DM

[Gerard Lemson]

Hi

> -----Original Message-----
> From: dm-bounces at ivoa.net <dm-bounces at ivoa.net> On Behalf Of Markus
> Demleitner
> Sent: Wednesday, September 4, 2019 5:29 AM
> To: dm at ivoa.net
> Subject: Re: PR#2 for Provenance DM
> 
> 
> Hi DM,
> 
> On Tue, Sep 03, 2019 at 01:31:39PM +0000, Gerard Lemson wrote:
> > > VO-DML as it stands already has a link to vocabularies through
> > > SemanticConcept, which, however, requires SKOS vocabularies.
> > This is not correct. Can be any semantic vocabulary, though what that
> > means we might want semantics WG to formalize further.
> > For this reason we renamed <<skosconcept>> to <<semanticconcept>>.
> 
> Excellent.  I should make it a habit to check the actual RECs (rather than my
> memory of early drafts) before blurting out publicly.
> 
> Looking at VO-DML REC-1.0, it says on semanticConcept/@vocabularyURI (p.
> 46):
> 
>   If this attribute is given a value, it indicates that the attribute
>   to which the SemanticConcept has been assigned MUST take values
>   from the vocabulary identified by the URI. It may be possible to
>   define a subset of its values using the topConcept attribute.
> 
> -- the topConcept part would be interesting if pulling things from, say, the
> UAT (which, incidentally, might be a good idea in SimDM), but I guess that's
> irrelevant here.
> 
Note that topconcept was indeed introduced in SimDM (then called broadestConcept) upon Norman Gray's suggestions.
He suggested that in the world of semantic (then SKOS) vocabularies one should be able to declare that an attribute should have a value that identifies a concept in some vocabulary, and that that concept must be narrower than the declared (top)concept. I.e. no restriction to a given vocabulary. 
This is very loose I think and may not be too useful for simple query engines that would prefer some predefined (though maybe extendable) list of valid values.
To support the latter purpose we have the vocabularyURI.

(Markus, do I read from this that you would be happier with the vocabularies in SimDM1.1 if we would only have a topconcept in our standard, rather than a vocabulary URI?
I am cc-ing Franck and Herve explicitly for this in case they're not listening to the DM mailing list)

One more thing. VO-DML does not say too much about *how* the attribute's value should identify the semantic concept.
This is a serialization issue. May also depend on the nature of the vocabulary maybe? In SKOS we assumed a URI.
Or, if the vocabularyURI was set in the model, the prefLabel of the concept might be sufficient.

Cheers
Gerard


> In what's left, there are two things that, now that we actually want to apply
> it, aren't quite to my taste.
> 
> (1) That the terms MUST come from the vocabulary may be a bit too harsh a
> constraint, in particular for the provenance people that so far have language
> like
> 
>   "Roles in relations to Agent are free text attributes, but if one
>   of the terms in Table 9 applies, it should be used."
> 
> It *is* a bit of a step from "if applies, ... should" to "must".
> Could the provenance folks perhaps give an indication if they'd go with the
> "must" from VO-DML if Semantics promise to have a lightweight process that
> will allow people quick and easy additions?
> My current idea is in sect. 4.2 of http://docs.g-vo.org/vocinvo2.pdf,
> and I'm fairly optimistic that we're ready to try something like this by the time
> ProvDM becomes REC.
> 
> The "must" certainly will help clients a lot to do interesting things, so if you
> can live with it, that would be great.
> 
> (2) VO-DML also says (p. 43):
> 
>   It is not necessary to indicate in the VO-DML model which of these
>   options has been chosen, since the URI which is the value of the
>   attribute will contain its own typing information.
> 
> This at least very strongly suggests that attributes controlled by a
> SemanticConcept should contain full URIs.  This means you'd write
> 
>   http://www.g-vo.org/rdf/datalink/core#bias
> 
> when all you really want to say is
> 
>   bias
> 
> -- that's a lot of boilerplate string for a vanishing benefit in case of
> SemanticConcepts that give a vocabulary URI (see also the URI vs. fragment
> discussion in http://mail.ivoa.net/pipermail/dm/2019-
> September/005936.html).
> 
> In that case, since VO-DML has the "must" just discussed, clients can already
> know that they have to prepend "http://.../core#" to every string.  I'd
> *really* like to exploit that knowledge and let them write just "bias".
> 
> So, I wonder if something that says:
> 
>   When a semanticConcept/@vocabularyURI is in force, the concept URI
>   is built as the simple string concatenation of the vocabulary URI
>   and the attribute value.
> 
> could be sneaked in as an Erratum to VO-DML?  Or is there anything in VO-
> DML that says there must be full URIs in such attributes?
> 
>         -- Markus