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Re: [xml-dev] Inherent limitation in the expressability of XML markup?

At 2011-03-21 07:22 -0400, Costello, Roger L. wrote:
>XPath is a non-XML syntax.
>Why isn't this co-constrain expressed using XML markup? Why do we 
>resort to non-XML syntax?

Because it is compact!

Note, Roger, that XQueryX has an XML vocabulary for XPath:


... an example from the spec ... who would want to write this each day?:


Not me!

>Does it indicate an inherent limitation in the expressability of XML markup?

It's verbosity.

>  Has anyone characterized this limitation?

When you have tools to interact with to create verbose XML syntax, 
then having a compact syntax is not as important.  But there is so 
much to say in an XPath address, that having the compact syntax is 
probably easier than creating a tool for the user interface for XPath.

Note in this regard that RELAX-NG has its own compact syntax that is 
isomorphic to the XML syntax.  When I'm not worried about 
composability or manipulating a RELAX-NG grammar, and I'm not using a 
tool, I far prefer writing a schema by hand in the compact 
syntax.  When I do need to machine-process a RELAX-NG grammar, I use XML.

Horses for courses.

I hope this helps.

. . . . . . . . . . Ken

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