[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: URIs harmful
>What are people's opinions on whether the authority which created the >URI can/should change which thing is being named? Great question! In an ideal world the mapping between URI and thing named, once created should remain constant, otherwise the whole identification business is pointless. This leads into the familiar dread region of what is actually being identified, which when talking of uri+url could be a document or what is returned by applying a certain algorithm to the identifier or numerous other interpretations. Permanent mapping of URIs is very close to the purl idea, but this has drawbacks - e.g. the clunkiness of datestamping the path for versioning (ugly & not easy to index by other means). Then there's the whole 'expires' business. The key I suppose is in the semantic interpretation : http://www.w3.org is the W3's home page (and namespace), the content of the document there may vary. The only way to square the circle is with metadata. For instance, being pragmatic I think we have to assume all URIs have a default property of 'transient'. If we're talking about something like a spec, then somewhere there should be information available describing the temporal and webspacial range of the resource mapped by the URI. This way the mapping remains constant, even if the resource that is the object of the mapping turns into a frog. A minor problem here is that interpretation of URIs by current agents is generally quite tightly coupled. I don't think this is a major issue in the sense used in the spurious 'expectation' argument regarding http: URIs - if the XML namespace is shown as a link in an editor or browser, that's the agent's fault, not the spec's. Backwards compatibility with broken systems isn't a good idea. However, for the transition to the Semantic Web to be a smooth as possible, the specs need to be as unambiguous as possible, and (IMHO) loosely coupled. It shouldn't be necessary to implement http: to use URIs with this prefix (it shouldn't be necessary to implement XML Schema just to publish (X)HTML pages, but that's another story...). A layering in which upper layers assume a set of defaults (like 'transient') which reflect the current state of the web I think is also desirable. Cheers, Danny.
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