W3C home > Mailing lists > Public > xml-dist-app@w3.org > April 2004

Re: Comments on initial draft of xml:id

From: <noah_mendelsohn@us.ibm.com>
Date: Fri, 9 Apr 2004 16:15:40 -0400
To: Elliotte Rusty Harold <elharo@metalab.unc.edu>
Cc: public-xml-id@w3.org, xml-dist-app@w3.org
Message-ID: <OF7E1B8562.BBA0A2E6-ON85256E71.006EEB31@lotus.com>

(note: distApp list included on this reply)

Elliotte Rusty Harold writes:

> "I'm not sure I agree with the statements "DTD authors should not
> declare attributes other than xml:id as type ID for interoperability
> with XML Schema- and non-validating processors. No interoperability
> guarantees are provided in these cases." and "XML Schema authors
> should not declare attributes other than xml:id as type xs:ID for
> interoperability with DTD- and non-validating processors. No
> interoperability guarantees are provided in these cases." There are
> just too many existing applications that use ID, Id, and id as
> ID-type attribute values. XHTML is one."

SOAP is another [1].

There are actually two things going on with SOAP that are worth
distinguishing.  The name of the attribute in question is soapenc:id [1],
not xml:id (making the obvious assumptions about prefix associations). This
distinction is important, as SOAP can be used to encapsulate existing
document fragments which may have their own uses for xml:id.  We do not
want any suggestion that a soapenc:ref attribute might be resolved by an
xml:id in such a fragment.  There are thus potentially two disjoint graphs
being carried within the same envelope.

For exactly that reason I have always had some personal doubts about our
XMLP decision to assign a 'type' of xs:ID, as we do.  Then again, the SOAP
processing model makes clear that schema validation is never required
anyway.

Keep in mind that (interestingly enough) use of the xs:ID type itself
implies no mandatory uniqueness constraint per the datatypes
recommendation. [2] Uniqueness is enforced only when doing schema
structures validation [3] (because, I believe, the datatypes rec has no
notion of a document scope, and the structures recommendation does).  So,
the xs:ID type assignment in the SOAP recommendation is more suggestive
than anything else.  In fact, the uniqueness constraint and corresponding
connection of soapenc:ref to soapenc:id are stated explicitly in the SOAP
recommendation, and are independent of the type assignment[4].

Noah

[1] http://www.w3.org/TR/soap12-part2/#idattr
[2] http://www.w3.org/TR/xmlschema-2/#ID
[3] http://www.w3.org/TR/2004/PER-xmlschema-1-20040318/#cvc-id
[4] http://www.w3.org/TR/soap12-part2/#uniqueidconstraints

--------------------------------------
Noah Mendelsohn
IBM Corporation
One Rogers Street
Cambridge, MA 02142
1-617-693-4036
--------------------------------------




                                                                                                                                        
                      Elliotte Rusty                                                                                                    
                      Harold                   To:       public-xml-id@w3.org                                                           
                      <elharo@metalab.u        cc:       (bcc: Noah Mendelsohn/Cambridge/IBM)                                           
                      nc.edu>                  Subject:  Comments on initial draft of xml:id                                            
                      Sent by:                                                                                                          
                      public-xml-id-req                                                                                                 
                      uest@w3.org                                                                                                       
                                                                                                                                        
                                                                                                                                        
                      04/09/2004 08:31                                                                                                  
                      AM                                                                                                                
                                                                                                                                        
                                                                                                                                        





I'm not sure I agree with the statements "DTD authors should not
declare attributes other than xml:id as type ID for interoperability
with XML Schema- and non-validating processors. No interoperability
guarantees are provided in these cases." and "XML Schema authors
should not declare attributes other than xml:id as type xs:ID for
interoperability with DTD- and non-validating processors. No
interoperability guarantees are provided in these cases." There are
just too many existing applications that use ID, Id, and id as
ID-type attribute values. XHTML is one. Is there any way to just note
the issue of interoperability, without making it as strong as a
"should"?

Section 4.3 states, "If those conditions are not satisfied then the
processor should report the error to the application.". Can this be
made more clear about "error"? In particular is this is a fatal or
non-fatal error?  Please, please don't let this be another of those
annoying cases where some parsers go one way and some go another. I
prefer this to be an explicitly non-fatal error, since that's more
backwards compatible.

Section 4.3 also states, "The attribute value must be a valid
NCName." I think this should be "The *normalized* attribute value
must be a valid NCName."

--

   Elliotte Rusty Harold
   elharo@metalab.unc.edu
   Effective XML (Addison-Wesley, 2003)
   http://www.cafeconleche.org/books/effectivexml

http://www.amazon.com/exec/obidos/ISBN%3D0321150406/ref%3Dnosim/cafeaulaitA
Received on Friday, 9 April 2004 16:16:35 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 7 December 2009 10:59:16 GMT