- From: Alistair Miles <alistair.miles@zoo.ox.ac.uk>
- Date: Thu, 23 Oct 2008 11:36:44 +0100
- To: public-swd-wg@w3.org
- Cc: public-esw-thes@w3.org
The second part of this comment needs some discussion before I can frame a response... Executive summary: It would be a good thing if the SKOS XL vocabulary could serve as an extension point for the provision of labels in other modalities, for example in accessibility-related use cases. To serve as an extension point, we have to either (1) live with the current XL data model, especially the restriction on the cardinality of skosxl:literalForm, which requires that all instances of skosxl:Label have exactly one plain literal form (even if they are intended to convey a label in another modality). or (2) relax the restriction on skosxl:literalForm, such that instances of skosxl:Label are not required to have a plain literal form (but if they do, they have at most 1) Personally, I think I favour (2), although it requires a substantive change to the SKOS Reference. Further discussion below... On Wed, Oct 08, 2008 at 09:54:57AM +0000, SWD Issue Tracker wrote: > > > ISSUE-180: Last Call Comment: PFWG: skosxl:Label class > > http://www.w3.org/2006/07/SWD/track/issues/180 > > Raised by: Everyone > On product: All > > Raised by Al Gilman on behalf of PFWG in [1]: > > """ [...] > The label framework should explicitly cater for non-textual labels in > image, audio or video format, and as provided in other markup > languages such as MathML. Labels in other modalities may serve as > alternate labels in accessibility-related use cases. SKOS should > provide guidance as to how to provide images, audio and video content > as alternate labels. Currently, icons are being standardized as > representing concepts in an upcoming multi-part standard ISO/IEC > 11581, developed by ISO/IEC JTC1 SC35. SKOS should be able to > specify these icons as part of a knowledge organization system. [...] > """ Currently the SKOS Reference defines skosxl:Label as "a special class of lexical entities". It also says that "each instance of this class has a single plain literal form...". This is reinforced by statement S53, where skosxl:Label is a sub-class of a restriction on skosxl:literalForm cardinality exactly 1. This raises a possible problem for use of the XL vocabulary as an extension point for extensions as described by Al above. For example, let's say a third party wants to extend the SKOS XL vocabulary to represent labels in various XML markup languages. They define extensions as follows: ex:XMLLabel rdf:type owl:Class ; rdfs:subClassOf skosxl:Label . ex:xmlLiteralForm rdf:type owl:DatatypeProperty ; rdfs:domain ex:XMLLabel ; rdfs:range rdfs:XMLLiteral . ex:xmlContentType rdf:type owl:DatatypeProperty ; rdfs:domain ex:XMLLabel . to be used as in e.g. <MyConcept> skosxl:prefLabel <MyXMLLabel> . <MyXMLLabel> rdf:type ex:XMLLabel ; ex:xmlLiteralForm """E = mc<sup>2</sup>""" ; ex:xmlContentType "application/xhtml+xml" . The potential problem is that the XL data model currently requires that *every* instance of xl:Label has a plain literal form. Therefore, the example above entails <MyXMLLabel> skosxl:literalForm _:aaa . where _:aaa is some as yet unknown plain literal. In practical terms, this means that every refinement of the skosxl:Label class should always give a plain literal form for the label, in addition to whatever other modality is the primary carrier of the label. >From an accessibility point of view this is not necessarily a bad thing. I.e. it's very roughly analogous to requiring alt text for images in HTML. However it is a bit restrictive for all cases. The alternative would be to relax the definition of the xl:Label class. So instead of """ A special class of lexical entities, called skosxl:Label, is defined. Each instance of this class has a single RDF plain literal form, but two instances of this class are not necessarily the same individual if they share the same literal form. """ we say something like """ This appendix defines a class called skosxl:Label. Each instance of this class has at most one RDF plain literal form, but two instances of this class are not necessarily the same individual if they share the same literal form. """ and we replace S53 with either """ skosxl:Label is a sub-class of a restriction on skosxl:literalForm cardinality at most 1. """ or (reverting to the previous model) """ skosxl:literalForm is an instance of owl:FunctionalProperty. """ What do you think? Cheers, Alistair. [1] http://lists.w3.org/Archives/Public/public-swd-wg/2008Oct/0063.html -- Alistair Miles Senior Computing Officer Image Bioinformatics Research Group Department of Zoology The Tinbergen Building University of Oxford South Parks Road Oxford OX1 3PS United Kingdom Web: http://purl.org/net/aliman Email: alistair.miles@zoo.ox.ac.uk Tel: +44 (0)1865 281993
Received on Thursday, 23 October 2008 10:37:32 UTC