Re: [xml-dev] Requirements on validation: (1) combine schemas, (2) divid

[noah_mendelsohn@us.ibm.com]

Roger Costello wrote:

> - It should be possible to divide non-monolithic documents into pieces
> and then validate each piece against one of the schemas.
> (divide-and-validate)
> 
> Do existing schema languages meet these requirements?
> 
> - No, you have to understand all  schemas very well and change them.
> - No, you have to validate the entire document against the combination
> of all schemas.
> 
>    - W3C XML Schema
>    - RELAX NG


I don't think you've accurately characterised the XSD language.  You can, 
to a significant degree, to incremenal validation if your validator 
supports it.  First of all, you can get a degree of modularity by using 
facilities like xs:include.  So, if you have an "outer" schema that 
includes a bunch of "inner" pieces, you can also often do validations 
using just the inner bits by identifying one or more of the inner schema 
documents to your schema processor when that's what you want. Furthermore, 
the Recommendation makes clear that [1]: 

"With a schema which satisfies the conditions expressed in Errors in 
Schema Construction and Structure (§5.1) above, the schema-validity of an 
element information item can be assessed. "

Note that the above does not refer to an entire XML document, but to a 
given element.  Of course, most validators take the option of validating 
whole documents and starting with the root, but that's not required.  You 
can in principle start with any element in the tree.  XSD does this in 
part so you can divide things, as Murata-san suggests, and in part so that 
tools like editors can do incremental revalidation as small parts of a 
document change.  The same section [1] points out that you can, in 
principle, identify any global element declaration or complex type to use 
in validating the element information item you've chosen.

I'm not saying that all of this provides everything that you or Murata-san 
might want, but it's a little strong to say that XSD does not meet the 
requirement at all.

Noah

[1] http://www.w3.org/TR/2004/PER-xmlschema-1-20040318/#validation_outcome
--------------------------------------
Noah Mendelsohn 
IBM Corporation
One Rogers Street
Cambridge, MA 02142
1-617-693-4036
--------------------------------------








"Costello, Roger L." <costello@mitre.org>
04/27/2008 04:33 PM
 
        To:     <xml-dev@lists.xml.org>
        cc:     (bcc: Noah Mendelsohn/Cambridge/IBM)
        Subject:        [xml-dev] Requirements on validation: (1) combine 
schemas, (2) divide a document into pieces and validate each piece, (3) 
use different schema languages, (4) validators work together


Hi Folks,

Here are a few snippets from slides by MURATA Makoto:

Requirements on validation#1

- It should be possible to combine schemas representing vocabularies
easily.

- It should be possible to divide non-monolithic documents into pieces
and then validate each piece against one of the schemas.
(divide-and-validate)

Do existing schema languages meet these requirements?

- No, you have to understand all  schemas very well and change them.

- No, you have to validate the entire document against the combination
of all schemas.

   - W3C XML Schema
   - RELAX NG

Requirements on validation#2

- It should be possible to use different schema languages for different
vocabularies.

- Validators for many schema languages should work together.

Do existing schema languages meet these requirements?

- No, you are forced to use one schema language.

- No, you have to use one validator.

   - W3C XML Schema
   - RELAX NG

More... www.asahi-net.or.jp/~eb2m-mrt/svgopen/200409SVGOpen.ppt

/Roger

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