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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: XHTML 2.0: the one bright light?? (Was: linking, 80/20)
 * Simon St Laurent | | No, it's the RDF mindset. RDF people are perfectly happy | manipulating URIs as identifiers, so they slap that into XML (via | namespaces) without concern for the endless conversations and | underspecified processing that model produces - to the labels used | by markup, no less. | | RDF itself hasn't poisoned XML directly, unless Liam Quin gets his | XMLr proposal through. RDF assumptions about the usefulness of URIs | as identifiers is downright toxic, however, when applied to XML. Hmmm. I think you can use URIs as identifiers without getting into difficulties over whether you regard them as locators or identifiers. RDF uses URIs in both ways, but the core RDF model does not make a distinction between these two cases. Without knowledge of specific RDF properties (essentially, application knowledge) there is no way to know whether a specific URI is an identifier or a locator. RDF's agnosticism about what URIs really denote is attractive in some ways, and apparently the logicians claim that it causes no difficulties, but it makes me somewhat uneasy for reasons I find difficult to fully articulate. I think I agree with your views on the symptoms (the badness of namespaces and suchlike), but I am not sure I agree about the nature of the disease, or even the existence of a specific disease causing these symptoms. Personally, I think URIs as identifiers is a great idea, and one that has the potential to solve many crucial problems in computing. In working with topic maps my views on what is important in information management have started to change, and I now think much more in terms of identity, distinctness, and sameness than I did before. I find this extremely helpful, and URIs to be a great help in this regard. I think topic maps provide a way for us to have this cake and also eat it, in the sense that topic maps let you use URIs as identifiers without losing sight of the fact that they are also locators. In RDF a URI identifies a resource, and the nature of the resource is beyond the scope of RDF. In topic maps, topics represent subjects (subjects being synonymous with resources in the RDF sense). A topic may have a URI which is the address of the resource, in which case you can go out and download the resource (or a copy thereof) from that URI. The URI would then appear in the [subject address] property in the data model. Of course, that URI then also identifies the resource, so that if some other topic has the same URI as its [subject address] you know that the two topics have the same resource as their subject (i.e. the topics represent the same subject). Of course, for subjects such a people, airports, and operas this does not work, since these subjects do not have URIs. In this case you can use a URI that points to a resource which describes (or indicates) that subject (and only that subject). In this case the URI goes in the [subject identifiers] property in the data model. If you later find another topic that has the same URI in that property clearly these two topics represent the same subject, since the resource only describes a single subject. In other words, topic maps allow you to use URIs as identifiers in a way that does not conflict with their nature as locators of information resources. RDF stays out of this territory altogether, and whether that is to its detriment or not is clearly something on which there is more than one opinion. BTW, the published subjects work is trying to create identifying URIs that are usable both in RDF and topic maps, but in accordance with the topic maps view of URIs. So far it seems to be succeeding. | See also the "patterns vs. identifiers" thread for a much more | detailed explication of why I think this mindset has caused grievous | and unnecessary harm to XML. I read that, and liked the beginning, but felt that the posting fizzled out before it really got started, which was a bit disappointing. A full-fledged article on this would have been interesting. -- Lars Marius Garshol, Ontopian <URL: http://www.ontopia.net > ISO SC34/WG3, OASIS GeoLang TC <URL: http://www.garshol.priv.no > 
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