Fw: Namespaces

Mark Birbeck Mark.Birbeck at iedigital.net
Wed Feb 3 19:49:33 GMT 1999

Clark - hope you don't mind but I'm copying this to the group because it
may be of interest.

Clark Evans wrote:
> Mark Birbeck wrote:
> > Using the expanded syntax from A.3 in the spec (sorry James,
> > yours is nice too), we get:
> Could you translate into the syntax James put forth, I think
> it much more clearly illustrates what's going on and 
> thus better facilitates conversation. Having to mentally translate
> what you wrote caused me to get a headache.  *evil grin*
> :) Clark
Sorry about your head Clark, but you can't translate because they
express two different things. James's syntax allows us to see what's
going on in an XML document by spelling out the namespaces to which
elements and attributes belong. So (from my email):

	<xml xmlns:n1="http://www.w3c.org" />
	<n1:good a="1" />
	<n1:good n1:a="1" />
	<n1:better a="1" />
	<n1:better n1:a="1" />


	<{http://www.w3c.org}good a="1" />
	<{http://www.w3c.org}good {http://www.w3c.org}a="1" />
	<{http://www.w3c.org}better a="1" />
	<{http://www.w3c.org}better {http://www.w3c.org}a="1" />

in James's syntax. However, I was expressing what position those
elements and attributes occupy in the XML namespace (again, from my
previous email):

> Our complete expanded list becomes:
>	<ExpEType name='good' ns="http://www.w3.org" />
>	<ExpEType name='better' ns="http://www.w3.org" />
>	<ExpAName name='a' eltype="good" elns="http://www.w3.org" />
>	<ExpAName name='a' eltype="better" elns="http://www.w3.org" />
>	<ExpAName name='a' ns="http://www.w3.org" />

Note that 'a' on 'good' has a unique entry, as does 'a' on 'better', but
in James's syntax we have 'a="1"' for both - i.e. no differentiation.

James's syntax is therefore a useful 'exploded XML' but has to be used
'in context' - because it is still expressing the original XML document.
But it does not tell us everything about the namespace (within the XML
namespace) that an element or attribute occupies. The expanded
attribute/element syntax loses information about the original XML
document, but *does* map the namespace structure.

As a shorthand in a previous email I used '^' between the various parts
that tell you where in the XML namespace structure an element or
attribute appears. So I could have expressed the above using:



	AETP is the 'all element types' partition
	PETP is the 'per-element-type' partition
	GAP is the 'global attribute' partition

Note that we have four namespaces (i.e. sets) within the greater XML
namespace. These are:


Not sure if that helps your headache, but it *is* a more accurate
representation of what is happening!

Mark Birbeck
Managing Director
Intra Extra Digital Ltd.
39 Whitfield Street
w: http://www.iedigital.net/
t: 0171 681 4135
e: Mark.Birbeck at iedigital.net

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