Mike,

Thank you very much for the feedback.

I've been able to use the schemas you referred to validate our DFDL4S schemas (or at least the general structure and the long forms annotations). I had to make a couple adaptations to the schema, to be able to load it with Xerces-C++ (there were some issues with the namespace xmlns:sub="http://www.w3.org/2001/XMLSchema") but it worked out in the end -- using a trivial resolver with a simple mapping between schema and location.

Regarding the validation of short form annotation, I'll try to leverage on the Xerces-C++ Schema Content Model to implement the check.

Again, thank you for the help.

-Marcos



On Thu, May 7, 2020 at 4:22 PM Mike Beckerle <mbeckerle.dfdl@gmail.com> wrote:

Marcos,

We use this approach in Apache Daffodil (incubating).

We use the schemas donated by IBM. Slight modifications have happened since them with new properties and such. We also created an XML schema for the DFDL subset of XSD.

There are two things you need to make this work. One is the schemas themselves. The other is a "resolver" which is a java class that finds and provides the included/imported file names given namespace URIs, and schemaLocation attributes. This resolver gets passed to Xerces. Your application can get away with a very stripped down resolver. We do have a full-featured one that you can use or learn from or adapt to your purposes.

One must still validate that short-form annotations are properly used, or transform them into long form before validation. The schemas will check that the dfdl prefix on things like dfdl:byteOrder="bigEndian" is valid and that byteOrder is a allowed attribute name, but doesn't check that dfdl:byteOrder="bigEndian" is placed on the right kind of XSD construct where byteOrder is allowed.

Similarly the property-element form like:

      <dfdl:element><dfdl:property name="byteOrder">bigEndian</dfdl:property></dfdl:element>

Also must be verified that the named property is relevant to the enclosing annotation. Or you can transform to the long form instead before validation. This requires escaping the value content.

If you clone the apache daffodil git repo, you can find schemas in 

    daffodil-propgen/src/main/resources/ org/apache/daffodil/xsd - schemas for the annotations (based on the ones originally created by IBM)

    daffodil-lib/src/main/resources/org/apache/daffodil/xsd - XMLSchema_for_DFDL.xsd - Schema for the DFDL subset of XML Schema.

The resolver we created searches class paths to find schema files in jars on the class path, or looks for an XML catalog. This is written in Scala.
It searches - (1) relative to current file containing the include/import (2) relative to the root of each jar on the class path in order (3) in an XML Catalog, found by way of a Catalog.properties file which itself is searched for on the class path.  We have found (1) and (2) above very helpful in building schemas up from other schemas packaged in jars.

It is in daffodil-lib/src/main/scala/org/apache/daffodil/xml/DaffodilLoader.scala - class DFDLCatalogResolver.

If you are using C/C++ code obviously this resolver will not apply, but something like what it does may be needed.

-mike


Mike Beckerle | OGF DFDL Workgroup Co-Chair | Owl Cyber Defense | www.owlcyberdefense.com
Please note: Contributions to the DFDL Workgroup's email discussions are subject to the OGF Intellectual Property Policy



On Thu, May 7, 2020 at 5:09 AM Steve Hanson <smh@uk.ibm.com> wrote:
Hi Marcos

IBM donated its set of meta schemas to the WG a while back.  Mike may know where they are located, I can't see them anywhere.

Regards
 
Steve Hanson

IBM Hybrid Integration, Hursley, UK
Architect, IBM DFDL
Co-Chair, OGF DFDL Working Group
smh@uk.ibm.com
tel:+44-1962-815848
mob:+44-7717-378890
Note: I work Tuesday to Friday



From:        "Marcos Bento (external)" <Marcos.Bento@esa.int>
To:        dfdl-wg@ogf.org
Date:        07/05/2020 08:38
Subject:        [EXTERNAL] [DFDL-WG] DFDL Meta-schema
Sent by:        "dfdl-wg" <dfdl-wg-bounces@ogf.org>




Hi,

I'm currently trying to find a way to automatically validate the schemas currently available/being developed in the scope of DFDL4S.
Is there an XSD that we could use as DFDL Meta-schema?

The current proposed approach is to make a small standalone XercesC-based utility to make the validation.
Do you have other/better suggestions?

-Marcos

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