Re: [xml-dev] So maybe ID isn't a problem after all.

[Bob Hutchison <hutch@xampl.com>]

On 01/11/13 10:48 AM, "Jim Ancona" <scarhill@yahoo.com> wrote:

> --- Bob Hutchison <hutch@xampl.com> wrote:
>> To represent these graph structures in a useful way, I've found that a
>> globally unique identifier is needed. This is because, in my experience,
>> some elements begin to appear in more than one document generated by the
>> application. In other words graph structures rarely are, in my experience,
>> confined to a single document. Something can be an ID and not satisfy the
>> practical requirements for graph representation.
> 
> A URI+fragment identifier IS a globally unique identifier (assuming that the
> fragment identifier points to an element named by an ID, as XPointer says). So
> cross-document graphs may be represented with a URI Reference interpreted as
> an
> XPointer Bare Name.
> 
> <snip/>
> 
>> So, I don't believe IDs are sufficient for the practical requirements of
>> graph structures, and XML doesn't support any kind of application
>> independent means of representing graph structures anyway.
> 
> What about XPointer?

XPointer still works through attributes, right? So you get things like
<replaceMe ref="..."/>. How does an application know, from XML syntax alone
that, the element should be replaced by what it is referring to? (I could be
more precise here I suppose: how is the application supposed to know that
the <replaceMe> element is identical to what it is referring to -- is that
English?) I thing that describing something as 'application independent'
(here) requires the existence of XML syntax that equates <replaceMe> with
what it is referring to.

Now, given that the application knows about graphing then using a URI to
specify the reference is certainly workable in many cases, I would imagine.
But this is getting pretty close to assuming a URL. In the project I was
referring to, a URL wouldn't work because the object wasn't locatable that
way. It was nameable (gosh) and so a URN would work. Do XPointers work with
URNs? 

Cheers,
Bob

> 
> Jim
> 
> =====
> Jim Ancona
> jim@anconafamily.com                     jancona@xevo.com
> 
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