The SKUA RDF vocabulary allows a number of assertions (or claims, or annotations) to be made concerning an object on the web, named by a URI. The vocabulary is defined as an RDF Schema.
The properties described here are at present rather volatile. Actually, very volatile – comments to Norman are welcome.
The SKUA namespace is
http://myskua.org/rdf/skua#,
and that is the long-term URI of this page.
Recall that RDF does not constrain the properties which may be asserted about an instance, thus it is perfectly reasonable to assert properties of a claim which are outside the SKUA namespace -- drawn from the Dublin Core set, for example -- as long as the domain implications of these assertions do not make the set of assertions inconsistent.
This is the base type of all the claims in the SKUA system.
The claim is an assertion made by the author of the claim, about the thing described as the object of the claim.
Note that the properties below, such as subject or tag, have as their domain the Claim, not the Object: the author is making the claim that these properties are so, but this may not be true in fact.
This is the class of things which have claims made about them. It can be anything named by a URI
Claim -> : The person making this claim. The range of this property is unspecified, but should be, in rough order of preference, a dereferenceable URI, a non-dereferenceable URI, an anonymous resource, which might have dublin core or FOAF properties describing it, a mailto resource, or a literal string.
Claim -> http://www.w3.org/2001/XMLSchema#string: The date on which the claim was made. This is a
subproperty of dcterms:created, and thus its format is W3CTDF, namely
yyyy-mm-dd[Thh:mm[:ss]TZD] (see http://www.w3.org/TR/NOTE-datetime)
Claim -> Object: Indicates the object of the claim, pointing to an Object resource
Claim -> http://www.w3.org/2008/05/skos#Concept: The subject of the resource the claim is about.
Unlike tag, this is a URI, which should have type skos:Concept
(see http://www.w3.org/TR/skos-reference). SKOS is a (still
draft) W3C standard for lightweight vocabularies. (Hmm: we
might loosen this range constraint).
See also the IVOA document (another draft standard)
'Vocabularies in the Virtual Observatory'
(http://www.ivoa.net/Documents/latest/Vocabularies.html).
Claim -> http://www.w3.org/2001/XMLSchema#string: A string tag annotating the rough type of the object. The value is a single string, with no spaces, and is taken as a folksonomy-style free-text label for the object, as distinct from subject, which is taken from a controlled vocabulary.
Object -> http://www.w3.org/2000/01/rdf-schema#Resource: The URI describing the Object
The following is an example of a SKUA claim, about the resource
http://en.wikipedia.org/wiki/Skua, where we assume that
the namespace http://foo/animals refers to a SKOS
vocabulary about animals:
@prefix : <http://myskua.org/rdf/skua#>.
@prefix ex: <http://foo/animals>.
@prefix dcterms: <http://purl.org/dc/terms/> .
<> a :Claim;
:object [
:uri <http://en.wikipedia.org/wiki/Skua>
];
:author <http://nxg.me.uk/norman/>;
:tag "skua", "wikipedia";
:subject ex:Bird;
:date "2008-08-13";
dcterms:description "All about a bad-tempered bird".
In RDF/XML, this looks like the following:
<?xml version="1.0" encoding="utf-8"?>
<rdf:RDF xmlns:dcterms="http://purl.org/dc/terms/"
xmlns:ex="http://foo/animals"
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns="http://myskua.org/rdf/skua#">
<Claim rdf:about="">
<author rdf:resource="http://nxg.me.uk/norman/"/>
<date>2008-08-13</date>
<object>
<rdf:Description>
<uri rdf:resource="http://en.wikipedia.org/wiki/Skua"/>
</rdf:Description>
</object>
<subject rdf:resource="http://foo/animalsBird"/>
<tag>skua</tag>
<tag>wikipedia</tag>
<dcterms:description>All about a bad-tempered bird</dcterms:description>
</Claim>
</rdf:RDF>