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Re: URIs harmful

• To: mike@s..., xml-dev@l...
• Subject: Re: URIs harmful
• From: "James Cerra" <jc2astro@h...>
• Date: Tue, 23 Jul 2002 10:16:24 -0400
• Bcc:

>"Non-dereferenceable identifier" would be an oxymoron, according
>to some, and depending on the definition of dereference, I would
>agree! :)

From a dereferenceable identifier: ( 
http://www.dictionary.com/search?q=dereference )

] dereference
]
] <programming> To access the thing to which a pointer points,
] i.e. to follow the pointer ... At first sight the word
] "dereference" might be thought to mean "to cause to stop
] referring" but its meaning is well established in jargon.
] (1998-12-15)

To me, the *big* question is whether or not a URI like a c-pointer or 
c-reference.  A pointer can be declared yet point to nothing, while a 
reference always points to something (and thus is always dereferenceable).  
According to the spec (rfc 2396):

] Not all resources are network "retrievable"; e.g., human beings,
] corporations, and bound books in a library can also be
] considered resources.

This means that, although all URIs are dereferenceable in general, a URI may 
not be dereferenceable in the virtual world where our applications reside.  
Further, the spec states that:

] The resource is the conceptual mapping to an entity or set of
] entities, not necessarily the entity which corresponds to that
] mapping at any particular instance in time.  Thus, a resource
] can remain constant even when its content---the entities to
] which it currently corresponds---changes over time, provided
] that the conceptual mapping is not changed in the process.

Obviously, this allows URNs to be URIs (if you want, I'll provide my 
reasoning).  That paragraph also has the side-affect that the resource's 
content may not be accessible (or even exist) at the same time as the URI.  
Thus, the reference of a URI may not be accessible because:

1) the content and URI processor are in different domains (Real World)
2) the content does not exist at the same time as the URI instance

This implies that URIs are analogous to c-pointers and not c-references - in 
general - and that "Non-dereferenceable identifier" is not an oxymoron.

---
Jimmy Cerra
http://subbieweb.tripod.com
"If the path is set in stone, use a sledgehammer"


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