XML query languages and their encodings

[Paul Prescod]

Mark Birbeck wrote:
> 
> I sort of guessed it might be ;-) I was more getting at the idea of
> context. The following is a 'list of nodes':
> 
>         <name>Mark</name>
>         <name>Tracey</name>
>         <name>Jan</name>

That's exactly my point. That's not a list of nodes. That's a list of XML
elements. Nodes are abstract. Here's a concrete representation for them
(and a containing element) for discussion purposes:

x= element( gi: "names",
       content:
             element( gi: "name", content: text( "Mark"))
             element( gi: "name", content: text( "Tracey"))
             element( gi: "name", content: text( "Jan")) )

Now in this abstract model a "list of nodes" is:

[x.content[0], x.content[1], x]

Do I know their context? Yes. Do I know their depth? Can I talk about
nodes of different depths? Yes. In this brain-dead simple abstract model
those issues are not complex at all.

Now if we want to encode these results for transmission between machines
then all of the issues you raise are important. But that is a *separate
issue*. It has nothing to do with the abstract concept of "node list".

"XML People" are encoding-focused so they always come back to the
encoding. That's fine but it is also important to recognize that some
things should be considered in the abstract domain -- like the result sets
of query languages.

-- 
 Paul Prescod  - ISOGEN Consulting Engineer speaking for only himself
 http://itrc.uwaterloo.ca/~papresco

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