Re: Are these two xpath expression equal?

There is a nice paper on equivalence of XPath queries:

Dan Olteanu, Holger Meuss, Tim Furche, and Fran cois Bry. XPath: Looking 
Forward. In Akmal B. Chaudhri, Rainer Unland, Chabane Djeraba, and 
Wolfgang Lindner, editors, EDBT Workshops, volume 2490 of Lecture Notes 
in Computer Science, pages 109-127. Springer, 2002.

Kind regards,
Maurice van Keulen.

Michael Kay wrote:

> They are different. Consider the document
>  
> <A>
>   <B>
>     <C/>
>   </B>
>   <B>
>     <D/>
>   </B>
> </A>
>  
> The first expression will select the <D/> element, the second will not.
>  
> The first expression selects a D using the path A/B/D provided that 
> the A owns a B which owns a C.
>  
> The second expression selects a D using the path A/B/D provided that 
> the B owns a C.
>  
> Michael Kay
>
>     ------------------------------------------------------------------------
>     *From:* [email protected] [mailto:[email protected]] *On
>     Behalf Of *Fianny Jiang
>     *Sent:* 03 September 2004 12:09
>     *To:* [email protected]
>     *Subject:* Are these two xpath expression equal?
>
>     Hi,
>      
>        I am puzzled whether the following two XPaht expressions will
>     return the same result.
>       (1)  A[B/C]/B/D
>       (2)  A/B[C]/D
>      
>       Or in other words, will (1) require that the matched pattern
>     should have two different B's?  That is C and D should have
>     different B as their parent.
>       Thanks alot.
>      
>     Regards,
>     Fianny 
>       
>

-- 
----------------------------------------------------------------------
Dr.Ir. M. van Keulen - Assistant Professor, Data Management Technology
Univ. of Twente, Dept of EEMCS, POBox 217, 7500 AE Enschede, Netherlands
Email: [email protected], Phone: +31 53 4893688, Room: INF3039
WWW: http://www.cs.utwente.nl/~keulen