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

Re: can you use inheritance (extension) in relax ng?

• To: Gustaf Liljegren <gustaf.liljegren@b...>
• Subject: Re: can you use inheritance (extension) in relax ng?
• From: Bob Foster <bob@o...>
• Date: Sun, 26 Oct 2003 13:26:36 -0600
• Cc: Dare Obasanjo <dareo@m...>, xml-dev@l...
• In-reply-to: <3.0.6.32.20031026154419.01025008@p...>
• References: <3.0.6.32.20031026154419.01025008@p...>
• User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.5) Gecko/20031007

Gustaf Liljegren wrote:
> At 06:54 2003-10-25 -0700, Dare Obasanjo wrote:
> 
>>As a document validation language RNG is simpler, more
>>expressive and less verbose than W3C XML Schema. As a
>>datayping language W3C XML Schema is the only game in
>>town [...]
> 
> Can you (or someone else) elaborate on this? I don't understand what
> features are missing från RNG as a "datatyping language" (what's that?). It
> has the existing datatypes from WXS, it has the ability to construct regex
> patterns, it has named patterns for complex types. What's not there?

RNG doesn't have type derivation. You can parameterize an existing type 
but you can't define a new named type based on an existing one.

RNG doesn't have "complex types" at all. One might argue that nothing is 
better than XML Schema's faux-OOP extension types, but a case could be 
made for named patterns. Some think it handy in a query language to 
know, e.g., that all arguments to a function match a certain pattern. 
(Some don't.)

More subtly, RNG is designed for validation, not type assignment. 
Because RNG patterns are closed under union, it can easily happen that a 
given sequence is valid according to more than one pattern, and there is 
no decision procedure to choose which pattern to use in assigning a 
type. XML Schema resolves such issues by a "first match" rule for its 
union (simple) types and by disallowing ambiguity in complex types.

> I think the day Microsoft turns to RNG will be a lucky day for XML.

Amen to that.

Bob Foster

> Gustaf
> 
> 
> -----------------------------------------------------------------
> The xml-dev list is sponsored by XML.org <http://www.xml.org>, an
> initiative of OASIS <http://www.oasis-open.org>
> 
> The list archives are at http://lists.xml.org/archives/xml-dev/
> 
> To subscribe or unsubscribe from this list use the subscription
> manager: <http://lists.xml.org/ob/adm.pl>
> 
> 

• Follow-Ups:
  • Re: can you use inheritance (extension) in relax ng?
    • From: James Clark <jjc@j...>
  • Re: can you use inheritance (extension) in relax ng?
    • From: Tim Bray <tbray@t...>

• References:
  • RE: can you use inheritance (extension) in relax ng?
    • From: Gustaf Liljegren <gustaf.liljegren@b...>

• Prev by Date: RE: Proposed Application for Literature
• Next by Date: Re: can you use inheritance (extension) in relax ng?
• Previous by thread: RE: can you use inheritance (extension) in relax ng?
• Next by thread: Re: can you use inheritance (extension) in relax ng?
• Index(es):
  • Date
  • Thread