I tend to agree that specifying urn for namespaces is better choice and URL should be used for schema locations; however convention of specifying URL for namespaces is long established some implementations use the namespace URL to return the actual schema. When I try to access the namespace URL for XML schema , it gives me reference to the document but not schema..

Suman Kalia
IBM Canada Lab
WMB Toolkit Architect and Development Lead
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From: Mike Beckerle <mbeckerle.dfdl@gmail.com>
To: dfdl-wg@ogf.org,
Date: 10/25/2012 08:18 AM
Subject: Re: [DFDL-WG] new action item needed: DFDL URN specification
Sent by: dfdl-wg-bounces@ogf.org

I wanted to add to this discussion the w3c blog page that highlights the problem of the http-based naming scheme. There are many articles about this, this is just one of them.

http://www.w3.org/blog/systeam/2008/02/08/w3c_s_excessive_dtd_traffic/

On Wed, Oct 24, 2012 at 10:35 AM, Mike Beckerle <mbeckerle.dfdl@gmail.com> wrote:

Introduction:

Using URLs as identifiers has caused no end of problems. E.g., in DFDL we have http://www.ogf.org/dfdl/dfdl-1.0/ as an identifier. W3C has http://www.w3.org/2001/XMLSchema and others.

W3C has badly regretted establishing this convention, as they have farms of servers that do nothing but quickly return 404 errors to save network-aware applications the network-timeout delay that would otherwise occur.

There are parties interested in exploiting DFDL who want DFDL schemas to NOT contain network URLs because it simply creates a concern about network access whenever a DFDL schema is inspected/used.

Pre-Proposal:

The new way to do this is with URNs which would look roughly like this: urn:ogf:dfdl:standard:dfdl-1.0. The whole point is that some other mechanism is used to establish correspondences between these and any resources in file systems, networks, or built-in to implementations. One such mechanism is called XML Catalog.

The point is that it is a name in a managed namespace which cannot be confused with a network protocol URL.

OGF is already establishing urn:ogf, and an ogf subgroup has already proposed urn:ogf:network for network resources. DFDL schemas aren't network resources so we don't want to be a substructure underneath network.

Some other mechanism is used to establish correspondences between these and any resources in file systems, networks, or built-in to implementations. One such mechanism is called XML Catalog.

Summary:

An action item should be to specify DFDL urn, submit to OGF as a proposed namespace, and then produce errata/spec changes to specify its use.

This requires a small design activity to specify a scheme for the sub-structure of the DFDL URNs (i.e., scheme for the stuff after urn:ogf:dfdl:...) where we want standard identifiers for versions of the standard, but we probably also want a few other things (e.g., I would like a space for implementations to identify themselves, i.e., an implementation-specific sub-area within our URNs.)

Our existing URLs can be compatible (deprecated) practice vs the preferred URNs.

--
Mike Beckerle | OGF DFDL WG Co-Chair
Tel: 781-330-0412

--
Mike Beckerle | OGF DFDL WG Co-Chair
Tel: 781-330-0412
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