[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message]

RE: Disk-based XPath Processing

  • From: "Michael Kay" <mike@s...>
  • To: "'Tatu Saloranta'" <cowtowncoder@y...>,"'Philippe Poulard'" <Philippe.Poulard@s...>,"'Uche Ogbuji'" <uche@o...>
  • Date: Tue, 3 Oct 2006 09:06:51 +0100

xpath selector unique subset
 
> On a related note: I noticed a reference (from Saxon-SA page, 
> I think) that implied that w3c schema specifies a n xpath 
> subset (perhaps for defining how key constraints can be 
> defined using subset of xpath?), like one that would be 
> useful for streaming access.
> Is this true?

This subset is specified at
http://www.w3.org/TR/xmlschema-1/#c-selector-xpath

(Actually it's two slightly different subsets, one for selectors and one for
fields. The general form of a uniqueness constraint in XML Schema is "within
every element E, each S must have a unique value for F": for example, within
every location, each employee must have a unique value for employee-number.
The "selector" is used to select S from E, the "field" is used to select F
from S.) 

The subsets are woefully small, unfortunately.

> Or are there other formal subset specifications, to make it 
> easier to know exactly what subset is (guaranteed to be) 
> supported by an implementation?

There are lots of academic papers on streaming XPath that have implemented
the parts of XPath that the researchers knew how to implement and left out
the bits they didn't (such is the privilege of academics). They aren't all
very good at revealing which bits they left out, but I don't think you'll
find one that can do preceding-sibling::*[3] or
following-sibling::*[last()-1].

Michael Kay
http://www.saxonica.com/



[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index]


PURCHASE STYLUS STUDIO ONLINE TODAY!

Purchasing Stylus Studio from our online shop is Easy, Secure and Value Priced!

Buy Stylus Studio Now

Download The World's Best XML IDE!

Accelerate XML development with our award-winning XML IDE - Download a free trial today!

Don't miss another message! Subscribe to this list today.
Email
First Name
Last Name
Company
Subscribe in XML format
RSS 2.0
Atom 0.3
 

Stylus Studio has published XML-DEV in RSS and ATOM formats, enabling users to easily subcribe to the list from their preferred news reader application.


Stylus Studio Sponsored Links are added links designed to provide related and additional information to the visitors of this website. they were not included by the author in the initial post. To view the content without the Sponsor Links please click here.

Site Map | Privacy Policy | Terms of Use | Trademarks
Free Stylus Studio XML Training:
W3C Member
Stylus Studio® and DataDirect XQuery ™are products from DataDirect Technologies, is a registered trademark of Progress Software Corporation, in the U.S. and other countries. © 2004-2013 All Rights Reserved.