• From: John Cowan <cowan@c...>
• To: xml-dev@l...
• Date: Thu, 13 Jan 2011 12:53:39 -0500

Michael Kay scripsit:

> Oh dear, yet another XPath subset. And they're all different. And most
> of them aren't subsets - few can resist adding something, though most
> people have the decency to do it by adding functions rather than new
> syntax.

That's all right with me, though it's verbose.

> Please, why is this needed?

To paraphrase James on MicroXML itself (and MicroXPath is meant for
use with MicroXML, not full XML): it is a subset (okay, almost) of
full XPath that is not intended to replace full XPath, but is intended
for contexts where full XPath is, or is perceived as, too heavyweight.
James goes on to say:

       One obvious objection is that there is no point
       in doing a subset now, because of the costs of XML
       complexity have already been paid.  I have a number
       of responses to this. First, XML complexity continues
       to have a cost even when XML parsers and other tools
       have been written; it is an ongoing cost to users
       of XML and developers of XML applications. Second,
       the main appeal of MicroXML should be to those who
       are not using XML, because they find XML overly
       complex. Third, many specifications that support
       XML are in fact already using their own ad-hoc
       subsets of XML (eg XMPP, SOAP, E4X, Scala). [...],

> And what were your criteria for deciding, say, that "|" or ">"
> aren't needed?

I made no such decisions.  I started from a base of "element names
separated by slashes" and worked up; I did not start from XPath 1.0 and
work down.  If there is a feature you think is indispensable, given the
reduced MicroXML data model (elements that have names, attribute maps,
and content sequences) and the intention of embedding MicroXPath in
conventional 3GLs rather than in some MicroXSLT (definitely not going
there), please let me know.  I welcome the voice of experience.

--
Even a refrigerator can conform to the XML      John Cowan
Infoset, as long as it has a door sticker       cowan@c...
saying "No information items inside".           http://www.ccil.org/~cowan
       --Eve Maler