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ACTION-363 - XRD correspondence with RDF

From: Toby Inkster <tai@g5n.co.uk>
Date: Thu, 17 Dec 2009 17:45:12 +0000
To: www-tag@w3.org
Message-ID: <1261071912.32395.346.camel@ophelia2.g5n.co.uk>
I was skimming the TAG minutes just now and noticed that TAG was looking
at this.

I recently implemented an XRD parser in Perl that parses XRD into an RDF
model (which can then, say, be queried with SPARQL or serialised as
N-Triples).

http://search.cpan.org/dist/XRD-Parser/

Most of XRD has an obvious mapping to RDF. Things that don't are:

1. <Alias> - I mapped this to a predicate:
<http://ontologi.es/xrd#alias>. owl:sameAs seems too strong an assertion
going by how I've seen it used in the wild.

2. Link templates - these I've mapped to a literal datatype. However,
because they're literals, they can't be used as RDF subjects in
subsequent statements, which means that if their media type, title, etc
are in the XRD, that information is lost from the RDF. A bnode mapping
might be a possibility.

I'm hoping to also write a package that serialises from an RDF model to
XRD and experiment with how well data can round-trip. Off the top of my
head, I'm pretty sure datatypes in RDF would get lost converting to XRD,
but probably not much else.

Here's an example of the conversion performed by the current version of
the parser.

========
<XRD xmlns="http://docs.oasis-open.org/ns/xri/xrd-1.0" xml:id="foo"
  xmlns:h="http://host-meta.net/ns/1.0">
  <Expires>1970-01-01T00:00:00Z</Expires>
  <h:Host>example.com</h:Host>
  <h:Host>www.example.com</h:Host>
  <Link rel="profile" template="http://services.example.com/profile?uri={uri}">
    <Property type="http://property.example.net/1">Foo</Property>
    <Property type="http://property.example.net/2">Bar</Property>
  </Link>
  <Property type="http://property.example.net/3">Baz</Property>
  <Link rel="another" href="/target" type="text/plain">
    <Title>Another</Title>
    <Property type="http://property.example.net/4">Quux</Property>
  </Link>
</XRD>
--------
<http://example.org/#foo> <http://xmlns.com/foaf/0.1/primaryTopic> <http://ontologi.es/xrd#host:example.com> .
<http://example.org/#foo> <http://ontologi.es/xrd#expires> "1970-01-01T00:00:00Z"^^<http://www.w3.org/2001/XMLSchema#dateTime> .
<http://ontologi.es/xrd#host:example.com> <http://property.example.net/3> "Baz" .
<http://ontologi.es/xrd#host:www.example.com> <http://property.example.net/3> "Baz" .
<http://ontologi.es/xrd#host:example.com> <x-xrd+template+for:http://www.iana.org/assignments/relation/profile> "http://services.example.com/profile?uri={uri}"^^<http://ontologi.es/xrd#URITemplate> .
<http://ontologi.es/xrd#host:www.example.com> <x-xrd+template+for:http://www.iana.org/assignments/relation/profile> "http://services.example.com/profile?uri={uri}"^^<http://ontologi.es/xrd#URITemplate> .
_:n0 <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/1999/02/22-rdf-syntax-ns#Statement> .
_:n0 <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://ontologi.es/xrd#host:example.com> .
_:n0 <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <x-xrd+template+for:http://www.iana.org/assignments/relation/profile> .
_:n0 <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> "http://services.example.com/profile?uri={uri}"^^<http://ontologi.es/xrd#URITemplate> .
_:n0 <http://property.example.net/1> "Foo" .
_:n0 <http://property.example.net/2> "Bar" .
_:n1 <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/1999/02/22-rdf-syntax-ns#Statement> .
_:n1 <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://ontologi.es/xrd#host:www.example.com> .
_:n1 <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <x-xrd+template+for:http://www.iana.org/assignments/relation/profile> .
_:n1 <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> "http://services.example.com/profile?uri={uri}"^^<http://ontologi.es/xrd#URITemplate> .
_:n1 <http://property.example.net/1> "Foo" .
_:n1 <http://property.example.net/2> "Bar" .
<http://ontologi.es/xrd#host:example.com> <http://www.iana.org/assignments/relation/another> <http://example.org/target> .
<http://ontologi.es/xrd#host:www.example.com> <http://www.iana.org/assignments/relation/another> <http://example.org/target> .
<http://example.org/target> <http://purl.org/dc/terms/format> <http://www.iana.org/assignments/media-types/text/plain> .
<http://example.org/target> <http://purl.org/dc/terms/title> "Another" .
_:n2 <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/1999/02/22-rdf-syntax-ns#Statement> .
_:n2 <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://ontologi.es/xrd#host:example.com> .
_:n2 <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.iana.org/assignments/relation/another> .
_:n2 <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> <http://example.org/target> .
_:n2 <http://property.example.net/4> "Quux" .
_:n3 <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/1999/02/22-rdf-syntax-ns#Statement> .
_:n3 <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://ontologi.es/xrd#host:www.example.com> .
_:n3 <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.iana.org/assignments/relation/another> .
_:n3 <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> <http://example.org/target> .
_:n3 <http://property.example.net/4> "Quux" .
========

Let me know if you have any questions. I'm not subscribed to this
mailing list, so please CC me if you want me to see it!

-- 
Toby A Inkster
<mailto:mail@tobyinkster.co.uk>
<http://tobyinkster.co.uk>
Received on Thursday, 17 December 2009 17:46:23 GMT

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