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Re: Modified proposal for 'provenance triple', ISSUE-110

From: Gregg Kellogg <gregg@kellogg-assoc.com>
Date: Tue, 30 Aug 2011 01:25:13 -0400
To: Ivan Herman <ivan@w3.org>
CC: W3C RDFWA WG <public-rdfa-wg@w3.org>
Message-ID: <8CC5A591-8B78-4F72-89A2-BCE046B0F150@greggkellogg.net>
On Aug 29, 2011, at 5:56 AM, Ivan Herman wrote:

After our discussion and the last telco, and subsequent emails, I would like to modify the proposal.

Proposal: for each RDFa source, the processor graph should contain one triple of the sort

- subject: URI referring to the processor graph (typically <> in Turtle, or @about="" in RDF/XML, though implementation MAY define a specific URI for that purpose)
- predicate: http://www.w3.org/ns/rdfa#hasSource (see also discussion below)
- object: the initial value of the base URI, as defined in 7.2 of the RDFa Core document

Processor Graph? I thought we had discussed placing it in the default graph.

As I discussed before, <> or @about="" end up resolving to the document's IRI or html>head>base, as they describe relative IRIs. It seems that what we need is an empty IRI output, so that another processor encountering a serialization of the original document will see that the document at a new IRI continues to describe the original location. Consider the following:

<html>
  <head>
    <base href="http://example.org/original"/>
  </head>
  <body about="">
    <p property="dc:title">Document Title</p>
  </body>
</html>

This will generate the following:

@base <http://example.org/original> .
<> dc:title "Document Title" ; rdfa:hasSource <> .

What you might want instead would be the following:

<> rdfa:hasSource <http://example.org/original> .
<http://example.org/original> dc:title "Document Title" .

The problem is, that as soon as the document is parsed, <> is given an actual URI (the base of the document being parsed), so I don't quite see how we accomplish this.

I have chosen the simplest possible way for the predicate URI, namely to define one for ourselves, which may not be the best. Ideas that came up during the discussion

- powder:describedby : but is it correct that the RDF content 'describes' the HTML content? THat may not necessarily be the case, it may give additional data that is not in the HTML

- foaf:primaryTopic (Virtuoso seems to use that): "property relates a document to the main thing that the document is about.", says the foaf spec; this is, in my view, closer than powder:described by

I think this is most appropriate.

- dcterms has a provenance property, but its range is defined as a 'ProvenanceStatement', which would then create (via RDFS) an extra type information on the original data, and I do not think that is fine

- The provenance vocabulary (http://purl.org/net/provenance/ns#) also has some predicates but, just as dcterms, it contains a number of range specification that yields extra types on the original base URI. I am not sure that is o.k. If we disregard that, then prv:accessedResource is probably the best one[1], it generates a type information of 'internet Resource'[2], which is fairly harmless. The problem is whether prv is stable enough for a Rec, though.

- The draft of the provenance model of the Prov WG seems to have a hasOriginalSource predicate (in section 6.4), but I am not sure whether this is stable.


The stable thing is to use our own predicate, and maybe define a sub-property relationship later when the provenance WG's terms gel. Alternatively, we can ask the Prov WG for their advice. I can live with primaryTopic, but it does not feel _really_ right either.

Ivan



[1] http://trdf.sourceforge.net/provenance/ns.html#accessedResource
[2] http://ontologydesignpatterns.org/ont/web/irw.owl#WebResource
[3] http://dvcs.w3.org/hg/prov/raw-file/default/model/ProvenanceModel.html

----
Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
mobile: +31-641044153
PGP Key: http://www.ivan-herman.net/pgpkey.html
FOAF: http://www.ivan-herman.net/foaf.rdf
Received on Tuesday, 30 August 2011 05:27:24 UTC

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