Re: comments and PIs in XML Schema

<gkholman@cranesoftwrights.com> wrote on 04/25/2009 01:04:13 AM:

<snip/>

> You won't see constraints on comments and PIs in DTD,

Not quite true. Elements declared to be EMPTY [1] in a DTD are forbidden
from containing comments, PIs and entity references (even ones whose
expansion is an empty string).

So a document such as:

<?xml version="1.0"?>
<!DOCTYPE root [
 <!ELEMENT root EMPTY>
]>
<root><?foo bar?></root>

isn't valid.

> W3C Schema, RELAX-NG or NVDL semantics.  I doubt any of the prototypical
> or bespoke XML vocabulary validation languages would constrain these
> either.  I suppose someone could dream up some validation semantics
> to constrain them, and implement them with something like
> Schematron.  But that would be more like a "document writing
> constraint" rather than an XML vocabulary constraint.

<snip/>

> . . . . . . . . . Ken
>
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[1] http://www.w3.org/TR/2008/REC-xml-20081126/#elementvalid

Michael Glavassevich
XML Parser Development
IBM Toronto Lab
E-mail: mrglavas@ca.ibm.com
E-mail: mrglavas@apache.org