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Re: Inherent limitation in the expressability of XML markup?

• From: Mukul Gandhi <gandhi.mukul@gmail.com>
• To: "Costello, Roger L." <costello@mitre.org>
• Date: Mon, 21 Mar 2011 18:55:23 +0530

Hi Roger,
    Other than the points mentioned, here's a significant capability
that's currently achievable using non-xml (the current syntax) XPath
syntax,

Using XPath expressions as values of attributes (that are computed at
runtime). Here's a fictitious example of this,

<X a="{sum(for $x in seq return $x mod 2)}">
 ...
</X>

This is used currently both in XSLT and XQuery.

On Mon, Mar 21, 2011 at 4:52 PM, Costello, Roger L. <costello@mitre.org> wrote:
> Hi Folks,
>
> XPath is a non-XML syntax.
>
> XSLT, Schematron, and XML Schema 1.1 make heavy usage of XPath. The role of XPath seems to expand with each new version of these technologies.
>
> Why?
>
> Example: consider this XML snippet:
>
> <meeting>
>    <start-time>08:00:00</start-time>
>    <end-time>09:00:00</end-time>
> </meeting>
>
> In both Schematron and XML Schema 1.1 the co-constraint between the meeting's start time and end time is expressed using XPath:
>
>  meeting/start-time lt meeting/end-time
>
> Why isn't this co-constrain expressed using XML markup? Why do we resort to non-XML syntax?
>
> Does it indicate an inherent limitation in the expressability of XML markup? Has anyone characterized this limitation?
>
> /Roger



-- 
Regards,
Mukul Gandhi

• References:
  • Inherent limitation in the expressability of XML markup?
    • From: "Costello, Roger L." <costello@mitre.org>