W3C home > Mailing lists > Public > public-grddl-wg@w3.org > April 2007

Re: issue-base-param

From: Chimezie Ogbuji <ogbujic@ccf.org>
Date: Mon, 16 Apr 2007 16:40:23 -0400
To: "GRDDL Working Group" <public-grddl-wg@w3.org>
Message-ID: <1176756023.5542.58.camel@otherland>

So I had a chance to come back to this thread as I was a bit disturbed
to find out that we don't have a normative dependency on the XML infoset
which would solve this problem.   

>> I am unclear whether the following  use of xml:base is relevant to
the 
>> following single element XML document
>> 
>> <r
>>     xmlns:g="http://www.w3.org/2003/g/data-view#"
>>     xml:base = "http://www.example.org/"
>>     g:transformation="xform" />
>> 
>> Should a GRDDL aware agent try to get http://www.example.org/xform for 
>> this example?

I don't think we have enough to information in the underlying model (the XPath data model) to properly resolve 'xforms' against 'http://www.example.org/'

> Oh?
> [[
> Given an XPath[XPATH] root node N with root element E, if the expression 
> /*/@*[local-name()="transformation"
>   and namespace-uri()=
>     "http://www.w3.org/2003/g/data-view#"]
> matches an attribute of an element E, then for each space-separated
> token REF in the value of that attribute, the resource
> identified[WEBARCH] by the absolute form (see section 5.2 Relative
> Resolution in [RFC3986]) of REF with respect to the base IRI of E is a
> GRDDL transformation of N.
> ]]

> The base IRI of E, in this case, is http://www.example.org/ .
> Or is it... XPath doesn't cite xml base... crud... don't
> tell me we need a normative dependency on the XQuery data model...

Yes, this is the problem.  XPath doesn't cite XML Infoset *or* XML Base and *doesn't* define any notion of a base URI for its nodes. 
The XML infoset OTOH *does* define a [base URI] for its Element Information Items.
So, basicaly, the xml:base = 'http://www.example.org/' in the concrete XML form is lost to the underlying XPath data model.

> Looks like infoset would be enough...

> "Several information items have a [base URI] or [declaration base URI]
> property. These are computed according to [XML Base]."
> http://www.w3.org/TR/xml-infoset/#intro.baseURIs

Yes, but our normative dependency on XPath only covers XML Names.  XPath defines expanded-names, children, and a string-value, but no notion of a base URI.

> Specific text changes welcome.

I think we simply need to be explicit about how "the base IRI of E" is determined.  It was pointed out to me that there is a precedent with XSLT which defines its own notion of a Base URI [1] since its
 dependent specifications (XML, XML Names, and XPath) don't cover this.  This is somewhat similar to our situation.

[[[
Every node also has an associated URI called its base URI, which is used for resolving attribute 
values that represent relative URIs into absolute URIs. If an element or processing instruction 
occurs in an external entity, the base URI of that element or processing instruction is the URI 
of the external entity; otherwise, the base URI is the base URI of the document. The base URI
 of the document node is the URI of the document entity. The base URI for a text node, a comment
 node, an attribute node or a namespace node is the base URI of the parent of the node.
]]]

I suggest we specify that we resolve the (space-seperated) values of data:transformation against the URI of the containing IR.
This would be consistent with our issue-base-param resolution.  The suggested text:

[[[
Given an XPath[XPATH] root node N of an information resource[WEBARCH] IR (an XML document), with root element E, if the expression 
/*/@*[local-name()="transformation"
  and namespace-uri()=
    "http://www.w3.org/2003/g/data-view#"]
matches an attribute of an element E, then for each space-separated
token REF in the value of that attribute, the resource
identified[WEBARCH] by the absolute form (see section 5.2 Relative
Resolution in [RFC3986]) of REF with respect to the IRI[RFC3987] from
which IR was resolved is a GRDDL transformation of N.
]]]

> I mostly think this is editorial, i.e. it doesn't merit re-opening
> issue-base-param. Harry, you might want to give that a think.

I agree.

[1] http://www.w3.org/TR/xslt#base-uri

-- 
Chimezie Ogbuji
Lead Systems Analyst
Thoracic and Cardiovascular Surgery
Cleveland Clinic Foundation
9500 Euclid Avenue/ W26
Cleveland, Ohio 44195
Office: (216)444-8593
ogbujic@ccf.org


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Received on Monday, 16 April 2007 20:40:40 GMT

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