[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: simple question on namespaces. (more arguing)
G. Ken Holman wrote: > Why invent a new way in the Internet world for ensuring > unique values in as many possible domains in a coherent > scheme? There is already one to use Well there are many other examples of syntax rules for values that are supposed to be unique, and each ruleset is tailored for generating IDs suited for a certain purpose. For example, there are competing syntax rules for: - the values of ID-type attributes in XML documents - Message-ID values in email headers - language 'tags' like fr-CA and x-klingon - the name or location of a resource -- a URI I do not see a good reason that URI syntax had to be the basis for identifying namespaces. It should not be a surprise that confusion ensues from this choice, since URIs were designed for a different purpose. They are *not* generic identifiers; they are intended to be used to identify the names and locations of resources. Whether the location or resource exists and/or is accessible is irrelevant, as has been mentioned repeatedly. But that doesn't change the fact that the URI identifies a location. Come on, is something so abstract as a namespace really a *resource* that can have a *location*? The URI spec says what the generic syntax is, and what URIs are generally used for. The URN spec and various protocol specs refine the syntax and intended usage a bit. I think the namespaces rec is the first one to come along and say "OK, forget what you know about URI semantics; we don't care about resource names and locations; we're just going to use the syntax for this other purpose." Maybe it's not necessarily wrong to do this, but they could have just as easily said they were going to use language tag syntax. People would be just as confused, then. I'm sure the post office has reserved a range of addresses for undeveloped property in your city. What if I came along and said I'm mass-producing widgets and need to give each one a serial number. I like the system your post office used for producing street addresses, so I'm going to use that as my serial numbering system. The IDs will read "7428 E. Main St.", "9683 Caldwell Ct.", etc. Oh, it's just a syntax, don't worry the fact that they look like real street addresses for homes and businesses. When I put them on my widgets, they're just for identifying the widget, that's all. What's all the fuss about? Your post office doesn't guarantee that there will be anything at every address it has on file, so why do you care if there's something at the addresses corresponding to my widget's serial number? I just told you the serial numbers don't correspond to addresses at all. It's just syntax! You'd probably call me a few names, wouldn't you? :) And actually, the syntax rules do not guarantee uniqueness of URIs, language tags, Message-IDs, etc. The namespaces rec actually says 2 separate things: the identifier must follow a certain syntax, and 2 identical identifiers refer to the same namespace. I would not call this a guarantee of uniqueness nor a formula for generating unique IDs. I also don't see any guarantee in the URI spec that a given resource can have only one URI. - Mike ____________________________________________________________________ Mike J. Brown, software engineer at My XML/XSL resources: webb.net in Denver, Colorado, USA http://skew.org/xml/
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