[oXygen-user] xml:id + docbook5 validation problems

Jesse Pelton
Mon Jun 29 12:57:54 CDT 2009

Section 4 of the xml:id specification says the normalized value of the attribute is an NCName and contains links to the NCName definitions for XML 1.0 and XML 1.1.  The XML 1.0 definition is easier to understand, but the XML 1.1 definition is more complete.  They're not equivalent; you should use IDs that conform to the specification for whichever version of XML you're using.

The restrictions on ID names are fundamental to XML.  Any decent introduction to XML should cover them, along with other stuff one simply has to know. 

-----Original Message-----
From:  [mailto:] On Behalf Of Robert Nagle
Sent: Monday, June 29, 2009 1:26 PM
To: Jirka Kosek
Subject: Re: [oXygen-user] xml:id + docbook5 validation problems


This is amazingly useful and nonobvious information.  I never would
have thought of this mistake.

Thank you.

I looked at the spec for xml:id  and I cannot seem to find a reference
to this requirement. Perhaps I am not understanding a concept or
terminology used on the spec page.


For future reference, how would I know about a requirement on an
attribute value like this one?

Robert Ngle

2009/6/28 Jirka Kosek <>:
> Robert Nagle wrote:
>> SystemID: I:\My Documents\xml\rj3\er1.xml
>> Engine name: oNVDL
>> Severity: error
>> Description: bad value for attribute "id" from namespace
>> "http://www.w3.org/XML/1998/namespace"
>> Start location: 2:80
>> *******************************
>> here is what I have in the er1.xml file:
>> <?xml version="1.0" encoding="UTF-8"?>
>> <chapter  xmlns="http://docbook.org/ns/docbook"   version="5.0" xml:id="99er1">
> IDs must start with letter (or underscore and few other characters) but
> not with number. This is cause of your error.
> --
> ------------------------------------------------------------------
>  Jirka Kosek      e-mail:       http://xmlguru.cz
> ------------------------------------------------------------------
>       Professional XML consulting and training services
>  DocBook customization, custom XSLT/XSL-FO document processing
> ------------------------------------------------------------------
>  OASIS DocBook TC member, W3C Invited Expert, ISO JTC1/SC34 member
> ------------------------------------------------------------------

Robert Nagle
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