• From: Philippe Poulard <Philippe.Poulard@s...>
• To: "Costello, Roger L." <costello@m...>
• Date: Tue, 19 Jun 2007 14:32:53 +0200

Hi Roger,

I noticed in "Two Types of XML Schema Language" 
(http://www.xfront.com/schematron/Two-types-of-XML-Schema-Language.html) 
the following sentence :
"No current schema language supports both grammar- and rule based 
validation"

A couple of years ago I designed the Active Schema Language (ASL) [1] 
which is something maybe "hybrid" : rather than having content models 
hard-coded in your schema, they are evaluated dynamically while 
validating ; this leads to much more powerful validation mechanisms than 
with traditional schema languages (DTD, Relax NG, W3C XML Schema, and 
Schematron).

There is a major drawback when Schematron is used in addition to one of 
these languages for checking a constraint that you can't express in 
grammar-based languages : for example, at an insertion point inside an 
editor, the user will be able to add an element allowed by the grammar 
that Schematron will reject after insertion. On the opposite, ASL act 
directly on the content model which can be built from additional rules.
You can download the implementation (RefleX) [2] and run an example that 
demonstrates this feature [3].

Moreover, ASL allows to define semantic data types, which is a feature 
available in many traditional programing languages, but curiously 
missing in XML schema languages.
Although experimental, there is also a runnable exemple available in 
RefleX [4].

I will talk about a feature of ASL (mixing declarative-oriented 
languages with imperative instructions, which allows to build content 
models dynamically) at Extreme Markup Language 2007 [5], as ASL is just 
an application of Active Tags [6]

[1] http://ns.inria.fr/active-tags/active-schema/active-schema.html ""
[2] http://reflex.gforge.inria.fr/
[3] http://reflex.gforge.inria.fr/tutorial.html#N80192D "XML validation 
with Active Schema"
[4] http://reflex.gforge.inria.fr/tutorial.html#N8019B7 "Playing with 
datatypes and PSVI"
[5] http://www.extrememarkup.com/extreme/2007/abstracts.html#t400r 
"Active Tags: Mastering XML with XML"
[6] http://ns.inria.fr/active-tags/

Costello, Roger L. a écrit :
> Hi Folks,
>  
> I have created a tutorial on Schematron:
>  
>       http://www.xfront.com/schematron
>  
> Comments welcome.
>  
> /Roger


-- 
Cordialement,

               ///
              (. .)
  --------ooO--(_)--Ooo--------
|      Philippe Poulard       |
  -----------------------------
  http://reflex.gforge.inria.fr/
        Have the RefleX !

• References:
  • ANN: Schematron Tutorial
    • From: "Costello, Roger L." <costello@m...>