Fw: [dfdl-wg] Ambiguous XPaths to hidden elements

[Suman Kalia]

I fully agree with Steve - let's not invent another XPATH like syntax ..

Suman Kalia
IBM Toronto Lab
WebSphere Business Integration Application Connectivity Tools 
Tel : 905-413-3923  T/L  969-3923
Fax : 905-413-4850
Internet ID : kalia at ca.ibm.com
----- Forwarded by Suman Kalia/Toronto/IBM on 01/19/2006 09:43 AM -----

Steve Hanson <smh at uk.ibm.com> 
Sent by: owner-dfdl-wg at ggf.org
01/19/2006 04:43 AM

To
"Westhead, Martin (Martin)" <westhead at avaya.com>
cc
dfdl-wg at ggf.org, owner-dfdl-wg at ggf.org
Subject
Re: [dfdl-wg] Ambiguous XPaths to hidden elements






As a DFDL parser implementor I do not want modifications to the XPath
syntax. I want to be able to reuse existing XPath implementations. It's
also something else for the user to have to learn. So 2a/b/c are not
attractive.

Regards, Steve

Steve Hanson
WebSphere Message Brokers,
IBM Hursley, England
Internet: smh at uk.ibm.com
Phone (+44)/(0) 1962-815848


 
             "Westhead, Martin 
             (Martin)" 
             <westhead at avaya.c                                          To 

             om>                       <dfdl-wg at ggf.org> 
             Sent by:                                                   cc 

             owner-dfdl-wg at ggf 
             .org                                                  Subject 

                                       [dfdl-wg] Ambiguous XPaths to 
                                       hidden elements 
             18/01/2006 20:24 
 
 
 
 
 




Hi folks,

This is to try to pick up on the issue identified by Suman in today?s 
call.

The Issue
Consider the following example:

<xs:element name="root">
<xs:complexType>
                                <xs:sequence>
                                                <xs:annotation><xs:appinfo
source=?http://dataformat.org? />
                                             <hidden>
<xs:element name="repeats" type="xs:integer"/>
                                                                </hidden>

</xs:appinfo></xs:annotation >
                                <xs:element name="testElement"
type="xs:integer " minOccurs=?0? maxOccurs=?unbounded?
                                 dfdl:repeatCount=?../repeats?>
                </xs:complexType>
</xs:element>

The problem is that the path ?../repeats? can be broken by modifications 
to
the logical model due to name clashes on ?repeats? and there are cases 
that
can be constructed where this would not be obvious to a user.

Possible Solutions
Possible fixes to this include:
   1.  Disallow  XPath  references to hidden elements the user is forced 
to
      place the material into the global context to refer to it.
   2.  Provide  a  special  XPath operator to indicate we are referencing 
a
      hidden element, possibilities include:
         a. ?../hidden(repeats)?
         b.  ?hidden(../repeats)?
         c.  ?../dfdl:hidden/repeats?
   3.  Only allow hidden elements to be present in top level global 
complex
      types. These can then be included where needed. (This is the 
solution
      that  Suman  was  pushing  but  I  don?t  fully  understand  it  ? 
in
      particular I don?t see how it resolves the ambiguity issue.)


I believe my preference here is 2a or 2b followed by 1.

Comments/suggestions/opinions?

Thanks,

Martin
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