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PER for POWDER

From: Phil Archer <phil@philarcher.org>
Date: Fri, 05 Nov 2010 17:24:36 +0000
Message-ID: <4CD43DD4.9030804@philarcher.org>
To: Public POWDER <public-powderwg@w3.org>
Hi,

Through a discussion on another list, I have realised that there is an 
error in the way we have defined the wdrs:describedby property: we give 
two conflicting definitions of the same thing. This has come to light 
when I've followed up on comments that people have made about the 
property that amount to "we can't use wdrs:describedby because it's 
specific to POWDER"

No!! It isn't - or at least, it shouldn't be. So here's the problem in 
detail.

In the first paragraph of section 4.1 [1] we say:

"...To facilitate linking between a described resource and a POWDER 
document we define a relationship type of describedby for use in (X)HTML 
link elements, HTTP Link Headers and ATOM feeds; and a textually 
identical term as part of the POWDER-S vocabulary. This is a generic 
relationship type that does not of itself imply that the link points to 
a POWDER document  that is done by the specific Media type. The formal 
definition of describedby is given in Appendix D."

Good. describedby is being used by POWDER but you only /know/ it's 
POWDER because of the MIME type in the link, not the use of describedby.

Appendix D is the formal definition of the describedby link relationship 
type, included, I'm delighted to say, in what is now RFC 5988 [2]. It says:

"The relationship A 'describedby' B asserts that resource B provides a 
description of resource A. There are no constraints on the format or 
representation of either A or B, neither are there any further 
constraints on either resource."

So far so good.

But... in section 4.1.4 [3] it says:

"We define the RDF property wdrs:describedby with a domain of 
rdf:Resource and a range of wdrs:Document. This is the class of POWDER 
documents and is a sub class of owl:Ontology. The meaning of 
wdrs:describedby is identical to the describedby relationship type 
defined above so that:

http://www.w3.org/2007/05/powder-s#describedby

and

http://www.iana.org/assignments/relation/describedby

have the same meaning and could be used interchangeably although the 
context in which they are used will usually determine which is the more 
appropriate."

This is false. http://www.iana.org/assignments/relation/describedby 
quite clearly makes no implications on the type of descriptive resource 
and yet here we are saying it has to be a POWDER doc which is a sub 
class on an OWL ontology.

The namespace document (both HTML and RDF representations) defines the 
range of wdrs:describedby.

People looking at this documentation see two places where we define a 
range for describedby and one where we don't. If describedby is to be 
used beyond POWDER - and there are many instances where it might be - we 
need to get this fixed as quickly as we can.

Proposal
========

1. Edit Section 4.1.4 of the DR doc to replace:

"We define the RDF property wdrs:describedby with a domain of 
rdf:Resource and a range of wdrs:Document. This is the class of POWDER 
documents and is a sub class of owl:Ontology. The meaning of 
wdrs:describedby is identical to the describedby relationship type 
defined above so that:"

with

"We define the RDF property wdrs:describedby, the meaning of which is 
identical to the describedby relationship type defined above so that:"

2. Edit the namespace document at 
http://www.w3.org/2007/05/powder-s#describedby so that wdrs:describedby 
has no defined range.

The latter is not in TR space and therefore can be edited without a lot 
of W3C process overhead (but not without agreement that this is the 
right course of action).

The former is a change to a Recommendation for which we need to follow 
the process as laid out at [4].

Does removing the range restriction on wdrs:decribedby affect 
conformance? The two conformance statements in the DR doc are not 
affected. However, unlikely as it may be, it is possible that someone 
has built an implementation that reasons that a wdrs:describedby 
property links to a POWDER document. Removing the restriction could 
conceivably have an adverse effect therefore. I believe this to be 
highly unlikely but it remains a possibility. Aside from that, the 
change is entirely backwards compatible.

In terms of the W3C process document I think we may come under 3.3 which 
says that:

"clears up an ambiguity or under-specified part of the specification in 
such a way that an agent whose conformance was once unclear becomes 
clearly conforming or non-conforming."

Conformance doesn't come into it but even so, an erratum may be 
insufficient and we may well have to seek a review for a "Proposed 
Edited Recommendation."

Incidentally, while we're at it, we could incorporate the existing 
erratum [5] which will help get the MIME type registered (this is still 
outstanding).

I would be most grateful for any comments on this.

Phil.

[1] http://www.w3.org/TR/powder-dr/#assoc-linking
[2] http://tools.ietf.org/html/rfc5988
[3] http://www.w3.org/TR/powder-dr/#semlink
[4] http://www.w3.org/2005/10/Process-20051014/tr.html#errata
[5] http://www.w3.org/2007/powder/powder-errata



-- 

Phil Archer
http://philarcher.org/
@philarcher1

Consultant                       |      W3C
Talis Platform                   |      Mobile Web Initiative
http://www.talis.com/platform/   |      http://www.w3.org/Mobile
Received on Friday, 5 November 2010 17:25:35 GMT

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