RE: issue-dbooth-9c: Base URI should only be required if needed

> From: Dan Connolly
> 
> Booth, David (HP Software - Boston) wrote:
> > This is a personal comment -- not on behalf of HP.  
> > 
> > As illustrated in the pipelining example at
> > 
> > http://lists.w3.org/Archives/Public/public-grddl-comments/2007
> > AprJun/0069.html
> > it is important that GRDDL also work for XML documents.  
> > Hence, the spec
> > should be clear that the lack of a base URI is only a 
> > problem if it is
> > needed (to resolve a relative URI) but not present.   I.e., 
> > correct and
> > complete GRDDL results should still be produced if there is 
> > no base URI
> > but all transformation tokens are absolute URI.
> > 
> > This is not currently clear in the spec.  In fact, the informative
> > "Mechanical Rules" seem to suggest that a base URI is 
> > always required in order to produce GRDDL results.  
> 
> It's an arbitrary decision whether to consider a base URI
> to be intrinsic to an XML document or extrinsic. That
> is
>    <doc1/> based at http://example/1
> and
>    <doc1/> based at http://example/2
> can be considered 2 distinct XML documents or 2 copies
> of on XML document.  GRDDL follows the Infoset
> spec in considering the base URI to be intrinsic to an
> XML document, so those are distinct XML documents.
> So formally, the base URI is always there.

The XML Infoset spec mentions Base URIs and says:
http://www.w3.org/TR/xml-infoset/#intro.baseURIs
[[
Several information items have a [base URI] or [declaration base URI]
property. These are computed according to [XML Base].
]]
however the Conformance section says:
http://www.w3.org/TR/xml-infoset/#conformance
[[
Specifications referring to the Infoset must:
    * Indicate the information items and properties that are needed to
implement the specification.
]]

My point is that the GRDDL spec should not require a base URI unless a
base URI is needed to resolve a relative URI.  If an XML instance
document does not have a URI and all of its URI references are absolute,
it would be silly to require it to have a base URI.

> 
> In practice, how you navigate all the relevant
> specs (HTTP, URI, ...) to find that base URI turns
> out to be fairly subtle. We have a number of fairly
> tricky cases worked out as test cases, and as a result,
> we're considering some clarifying text. See
> 
>   progress on documenting base
>   
> http://lists.w3.org/Archives/Public/public-grddl-wg/2007May/0088.html

Okay, so as part of clarifying the base URI text, I think it would be
good to make clear that GRDDL only requires a base URI if the XML
instance document contains a relative URI reference.  AFAICT this would
be consistent with RFC 3986, which says:
http://www.apps.ietf.org/rfc/rfc3986.html#sec-5.1.4
[[
A sender of a representation containing relative references is
responsible for ensuring that a base URI for those references can be
established.
]]

Thanks,

David Booth, Ph.D.
HP Software
+1 617 629 8881 office  |  dbooth@hp.com
http://www.hp.com/go/software

Received on Wednesday, 30 May 2007 18:57:53 UTC