RE: Assumptions about URIs
John Cowan said: "On this basis, "John Cowan" is a non-URI name of *me*, whereas mailto:cowan@c..." is a URI name of *one of my mailboxes*." Is 'A URI name' an oxymoron when applied to a URL? There is a danger of getting names and references mixed up here (not to speak of 'definite descriptions'). RFC 2396 says: "A Uniform Resource Identifier (URI) is a compact string of characters for identifying an abstract or physical resource." And later: "A URI can be further classified as a locator, a name, or both. The term "Uniform Resource Locator" (URL) refers to the subset of URI that identify resources via a representation of their primary access mechanism (e.g., their network "location"), rather than identifying the resource by name or by some other attribute(s) of that resource. The term "Uniform Resource Name" (URN) refers to the subset of URI that are required to remain globally unique and persistent even when the resource ceases to exist or becomes unavailable." So a URL is an identifier by location not by name. I would call this a reference. 'John Cowan' is a name of John Cowan (though not a URN). The name of the mailbox cowan@c... is 'cowan@c...' not mailto:cowan@c.... The mailto is a reference to that mailbox (part of which happens to be its name). In other words, the fact that mailto:cowan@c... is a URL not a URN makes it a reference (by location) rather than a name. Does this matter? I think it does. A reference to an object is not the same as its name (this is the difference between an object's 'handle' and its 'key' in EJB terms). I can de-reference a reference to get the object, but I can't de-reference a name (in general). On the other hand, references to an object are specific to the way the de-referencing is done whereas names are independent of the way they are de-referenced (and they persist across object instantiations). They are therefore used for different purposes. It seems as though the problem with namespaces is that they use a method for referencing resources to name abstract resources. John F Schlesinger SysCore Solutions -----Original Message----- From: John Cowan [mailto:cowan@m...] Sent: 04 March 2002 12:01 To: Bent Rasmussen Cc: xml-dev@l... Subject: Re: Assumptions about URIs Bent Rasmussen scripsit: > - "Does the URI 'http://www.w3.org' identify an > organisation called W3C or a location on the Web?" For informal purposes, it can refer to either, just as informally I can be called either "John Cowan" or "mailto:cowan@c...". For RDF/TM purposes, when it is necessary to make rigorous distinctions, then there are two possible answers: - A URI means what the owner of the authority-part (DNS name) says it means. On this basis, "John Cowan" is a non-URI name of *me*, whereas "mailto:cowan@c..." is a URI name of *one of my mailboxes*. - The meaning of a URI must be inferred from the statements made about it. In this case we would have to look to what has been said. -- John Cowan http://www.ccil.org/~cowan cowan@c... To say that Bilbo's breath was taken away is no description at all. There are no words left to express his staggerment, since Men changed the language that they learned of elves in the days when all the world was wonderful. --_The Hobbit_ ----------------------------------------------------------------- The xml-dev list is sponsored by XML.org <http://www.xml.org>, an initiative of OASIS <http://www.oasis-open.org> The list archives are at http://lists.xml.org/archives/xml-dev/ To subscribe or unsubscribe from this list use the subscription manager: <http://lists.xml.org/ob/adm.pl>
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