IBM DFDL has handled its DFDL extensions using short-form attributes on the xsd objects and not the annotations.

Regards

Steve Hanson
Architect, IBM Data Format Description Language (DFDL)
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh@uk.ibm.com
tel:+44-1962-815848

From: Mike Beckerle <mbeckerle.dfdl@gmail.com>
To: dfdl-wg@ogf.org,
Date: 27/03/2013 02:54
Subject: [DFDL-WG] Are non-native attributes allowed on DFDL annotation elements?
Sent by: dfdl-wg-bounces@ogf.org

In XML Schema you are allowed to throw in attributes even just as documentation i.e.,

<xs:element xmlns:rtfm="read:the:..manual." name="myElement" rtfm:yo="this element name is general lameness" .../>

I.e, in the definition of xs:element there is this wildcard with standard lax validation for any non-native attributes.

So, the question is do we want to also allow that on dfdl annotation elements, i.e,

<dfdl:format byteOrder="bigEndian" rtfm:yo="it's LE Loser!" />

Given that you cannot nest  inside element syntax, these non-native attributes are the only convenient way to add commentary to the attributes of a XML document.

Another perhaps more compelling reason to tolerate this is that I am sure in the next year all the DFDL implementation efforts are going to add some new experimental properties, and we will want to hang them on the same dfdl annotation elements. Schema inter-operation requires us each to tolerate the other's such experimental properties to the extent that they are not essential to the schema being usable at all.

So if I have:

<dfdl:element dafext:recursive="typesOnly" xmlns:dafext="some.daffodil.urn.for.extensions" ref="someOtherFormat" />

then we will want IBM DFDL and DFDL implementations generally, to perhaps warn that it was there and unrecognized, but not to just SDE on non-validation.

Today, the XML Schemas for DFDL Annotations do not allow non-native attributes inside DFDL annotation elements, but the spec is silent on the subject.

I was considering adding a couple of experimental properties (not right away, but maybe by year end), and I only realized today that they would break compatibility without a change here.

Comments?

--
Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | www.tresys.com
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