Re: XPath conformance? was RE: [xml-dev] storing XML files

[Tom Bradford <bradford@dbxmlgroup.com>]

Evan Lenz wrote:
> For example, the following is not in compliance with the XPath spec:
> 
> /customer[name ~= "Mike"]
> 
> whereas this alternative expression would be perfectly fine:
> 
> /customer[ext:like(name, "Mike")]

Though the first example is not part of the specification itself, the
second example is an extension function that most implementations will
not support.  In the case of common behavior in the context of XML
databases, neither is 'right'.  One won't even be parsable by a
generalized XPath processor, and the other will only be resolvable in a
single implementation, so nobody is wrong or right.  The goal, which I
spoke about before, should not be who is more compliant, because
compliancy with what the W3C produces doesn't address the larger and
more common problems that we face as vendors/users of XML databases.

The first example is similar to Microsoft adding '*=' to SQL for left
outer joins, where the second is somebody adding a function to SQL
called LEFTOUTERJOIN().  While the LEFTOUTERJOIN function can be parsed
by a compliant SQL parser, nobody will support it, so it buys you
nothing to comply with the grammar.  Our real goal should be to define a
common use case and a common implementation, rather than point fingers.
 
-- 
Tom Bradford
The dbXML Project
Open Source Native XML Database
http://www.dbxml.org