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Posted by John Dunlop on 11/10/06 11:27
Jerry Stuckle:
> [A URL] describes a resource.
Well, URLs by definition _locate_ network locatable resources,
specifically 'information resources', as one W3C Recommendation calls
them; whether or not the string of characters in a URL describes in
some human-recognisable way the resource it points to is up to you the
URL owner.
> One of the types of resource it describes is a file.
The crux of the matter is that if a URL points to a particular
representation of a resource - e.g., HTML, XHTML, plain text, RTF - and
this is reflected in the URL in the shape of suffixes, when you change
the representation or add another representation and negotiate between
them you have to change the URL to keep it meaningful. For example, if
you originally publish a restaurant menu in plain text, ending its URL
path with '.txt', but later publish an HTML version and negotiate
between the two, the '.txt' at the end of the URL path is counter
intuitive for the HTML version.
You could solve this in one of two ways. One, publish two different
URLs, one ending in '.txt', the other in '.html'. However, this
undermines the value of the resource since it divides the community
into those who refer to the plain text version and those who refer to
the HTML version while for everyone the resource is conceptually a
single entity; c.f., Metcalfe's Law. Two, instead of seeing the URL as
pointing to a particular representation of the resource, see the URL as
pointing to the resource itself - the menu in the example above. That
way, when you change or add representations, you don't need to change
the URL because it identifies the resource itself rather than any
particular representation. Which way you choose depends on what you
see the URL as pointing to.
If you choose the second way, URL suffixes have no place in URLs
because they add nothing to the identification of the resource and they
run afoul of the principles of length (shortness), meaningfulness, and
persistency. I regard as weak the counter argument that if URL
suffixes are a de facto standard, then all URLs should include them.
The BBC, for example, publishes URLs without suffixes, and URLs without
suffixes occur in traditional media. Even if URL suffixes are a de
facto standard, the suffix-less ones are more user friendly.
--
Jock
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