Re: 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: http://www.w3.org/TR/xqueryx/ ... an example from the spec ... who would want to write this each day?: <xqx:pathExpr> <xqx:stepExpr> <xqx:filterExpr> <xqx:functionCallExpr> <xqx:functionName>doc</xqx:functionName> <xqx:arguments> <xqx:stringConstantExpr> <xqx:value>http://bstore1.example.com/bib.xml</xqx:value> </xqx:stringConstantExpr> </xqx:arguments> </xqx:functionCallExpr> </xqx:filterExpr> </xqx:stepExpr> <xqx:stepExpr> <xqx:xpathAxis>child</xqx:xpathAxis> <xqx:nameTest>bib</xqx:nameTest> </xqx:stepExpr> <xqx:stepExpr> <xqx:xpathAxis>child</xqx:xpathAxis> <xqx:nameTest>book</xqx:nameTest> </xqx:stepExpr> </xqx:pathExpr> 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 -- Contact us for world-wide XML consulting & instructor-led training Crane Softwrights Ltd. http://www.CraneSoftwrights.com/x/ G. Ken Holman mailto:gkholman@CraneSoftwrights.com Legal business disclaimers: http://www.CraneSoftwrights.com/legal
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