[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message]

Re: should all XML parsers reject non-deterministic content models?

  • From: Joe English <jenglish@f...>
  • To: xml-dev@l...
  • Date: Sun, 14 Jan 2001 09:58:16 -0800

xml non deterministic

TAKAHASHI Hideo wrote:

> I understand that the XML 1.0 spec prohibits non-deterministic (or,
> ambiguous) content models (for compatibility, to be precise).
> Are all xml 1.0 compliant xml processing software required to reject
> DTDs with such content models?

No: a processor can ignore the DTD entirely and still be compliant.
And since the prohibition against non-deterministic content models
appears in a non-normative appendix, I would presume that conforming
DTD-aware processors are not required to detect this condition either.
Even in full SGML, ambiguous content models are a "non-reportable
markup error", i.e., parser don't need to detect this condition.

> Ambiguous content models doesn't cause any problems when you construct a
> DFA via an NFA.  I have heard that there is a way to construct DFAs
> directly from regexps without making an NFA, but that method can't
> handle non-deterministic regular expressions.

There are many, many other ways to validate documents against content
models though.  Take a look at James Clark's TREX implementation,
which has no problem with ambiguity, and also efficiently handles
intersection, negation, and interleaving of content models
(the first two of which are *very* expensive in a DFA-based
approach).


> If you choose that method
> to construct your DFA, you will surely benefit from the rule in XML 1.0
> . But if you choose not, detecting non-deterministic content models
> become an extra job.

But note that detecting ambiguity in XML content models is considerably
simpler than in SGML -- the really difficult part involves '&' groups
which aren't present in XML.


--Joe English

  jenglish@f...

PURCHASE STYLUS STUDIO ONLINE TODAY!

Purchasing Stylus Studio from our online shop is Easy, Secure and Value Priced!

Buy Stylus Studio Now

Download The World's Best XML IDE!

Accelerate XML development with our award-winning XML IDE - Download a free trial today!

Don't miss another message! Subscribe to this list today.
Email
First Name
Last Name
Company
Subscribe in XML format
RSS 2.0
Atom 0.3
 

Stylus Studio has published XML-DEV in RSS and ATOM formats, enabling users to easily subcribe to the list from their preferred news reader application.


Stylus Studio Sponsored Links are added links designed to provide related and additional information to the visitors of this website. they were not included by the author in the initial post. To view the content without the Sponsor Links please click here.

Site Map | Privacy Policy | Terms of Use | Trademarks
Free Stylus Studio XML Training:
W3C Member
Stylus Studio® and DataDirect XQuery ™are products from DataDirect Technologies, is a registered trademark of Progress Software Corporation, in the U.S. and other countries. © 2004-2013 All Rights Reserved.