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Modules and Ontologies
RSS 1.0 includes also a concept of modules using XML namespaces. The idea is to provide room for meta data for channels, items, etc. While it strikes odd that a notation based on RDF uses yet another concept, following modules are usually shipped with supporting software: The Dublin Core (DC) module contains properties from a more librarian point-of-view, Syndication (syn) may add channel and item properties relating to syndication issues whereas Taxonomy (taxo) would be the place to add categories to channel information.
In the case of DC, it is straightforward how to translate the DC concepts there into a topic map vocabulary:
DC (ontology) bn : the Dublin Core oc (definition): http://dublincore.org/documents/dces/ in : Dublin Core Metadata Element Set Language (ontology-element) is-part-of DC bn: Language in (definition): A language of the intellectual content of the\ resource. in (comment): Recommended best practice for the values of the\ Language element is defined by RFC 1766 [RFC1766] which\ includes a two-letter Language Code (taken from the ISO 639\ standard [ISO639]), followed optionally, by a two-letter\ Country Code... Creator (ontology-element) is-part-of DC bn : Creator in (definition): An entity primarily responsible for making\ the content of the resource. in (comment): Examples of a Creator include a person, an\ organisation, or a service. Typically, the name of a\ Creator should be used to indicate the entity. Rights (ontology-element) is-part-of DC bn: Rights Management in (definition): Information about rights held in and over the\ resource. in (comment): Typically, a Rights element will contain a rights\ management statement for the resource, or reference a service\ providing such information. Rights information often .... ...
The only challenge now is to integrate this new base vocabulary into our set of constraints. For this purpose, let us consider the following RSS snippet containing module information:
<rdf:RDF
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns="http://purl.org/rss/1.0/"
xmlns:dc="http://purl.org/dc/elements/1.1/"
>
<channel rdf:about="http://www.xml.com/">
<title>XML.com</title>
<link>http://www.xml.com/</link>
<description>XML.com features a rich mix of information and
services for the XML community.</description>
<dc:language>en-us</dc:language>
<dc:rights>Copyright 2000, O'Reilly and Associates</dc:rights>
<dc:publisher>edd@xml.com (Edd Dumbill)</dc:publisher>
<dc:creator>peter@xml.com (Peter Wiggin)</dc:creator>
</channel>
....
</rdf:RDF>
According to this, the channel contains meta information holding its
language, some copyright note, the publisher and the author (creator).
In a Topic Map representation of a channel we will have to associate
these properties with channels or items. For this we have two
options: If we would commit ourselves to a particular vocabulary, then
we could handcraft appropriate associations (assuming
t-0000000000 is the topic id of the corresponding
channel topic above):
(is-for-language) Language : t-0000000001 text : t-0000000000 t-0000000001 bn: en-us (holds-rights) Rights : t-0000000002 content : t-0000000000 t-0000000002 bn: Copyright 2000, O'Reilly and Associates (is-publisher-of) Publisher : t-0000000003 content : t-0000000000 t-0000000003 bn: edd@xml.com (Edd Dumbill) (is-creator-of) Creator : t-0000000004 content : t-0000000000 t-0000000004 bn: peter@xml.com (Peter Wiggin)
The crux with this approach is that any processor would have to understand these associations. While this is reasonable for DC, it is not obvious how to cope with arbitrary modules which might appear in an RSS document.
As a suboptimal alternative we can keep the additional meta data as property of the channel (and also other parts of the maps).
(is-property-of) holder : t-0000000000 property : Language value : t-0000000001 ontology : DC t-0000000001 (property-value) bn: en-us (is-property-of) holder : t-0000000000 property : Rights value : t-0000000002 ontology : DC t-0000000002 (property-value) bn: Copyright 2000, O'Reilly and Associates ...That way we maintain some degree of genericity sacrificing the explicitness in the maps.
As a consequence we have to extend our set of constraints to cater properties for channels, items and images. See the TMSS constraints and the DC AsTMa= definition for details.
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