Determining Complete GRDDL Results

Status of this Document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. @@Add standard verbiage here@@

This document is not (currently) a product of the GRDDL working group or the W3C. It is a draft that was produced independently by the author(s) for consideration by the GRDDL working group. If this document is adopted as a work product of the GRDDL working group, then it will be moved from its current location to the W3C web site.

This document builds on the GRDDL specification, which is hereby incorporated by reference, and makes use of several terms defined therein. Readers should be familiar with that document before reading this one.

Normative assertions are marked up in this way.

Introduction

GRDDL is used "to complement the concrete RDF/XML syntax with a mechanism to relate other XML syntaxes . . . to the RDF abstract syntax"[GRDDL Charter].

The GRDDL specification defines the notion of GRDDL results and the process that GRDDL-aware agents should use to compute GRDDL results from an XML document. The process is intentionally variable: for security and other reasons, the GRDDL-aware agent is not required to compute all possible GRDDL results for that XML document.

In some cases, a GRDDL transformation author may wish to be very precise about the exact set of RDF triples that the GRDDL transformation is intended to denote when applied to a particular XML document. Similarly, the user of that XML document may want to know whether the GRDDL results that his/her GRDDL-aware agent produced constitute all of those triples. This can be important in applications where XML documents are treated as custom serializations of RDF, and GRDDL is used to "relate their syntax to RDF/XML"[GRDDL Charter]. Without a commonly accepted definition of "complete GRDDL results", users may unknowingly receive different subsets of the intended RDF triples from different GRDDL-aware agent implementations -- each labeled "complete GRDDL results". The purpose of this document is therefore to provide a common definition of "complete GRDDL results".

A GRDDL-aware agent is not required to compute complete GRDDL results. However, a GRDDL-aware agent choosing to implement this Note:

SHOULD provide an option to specify whether complete GRDDL results are preferred (though this option should not take precedence over security considerations); and, if so, the GRDDL-aware agent
SHOULD attempt to determine them (subject to security considerations) ; and
SHOULD provide a means of indicating whether the actual GRDDL results obtained from a particular XML document (representation) are known to constitute:

the complete GRDDL result;
a subgraph of the complete GRDDL result; or
neither.

To facilitate the determination of complete GRDDL results, this Note defines an optional attribute in the GRDDL namespace, grddl:complete, and a metadata profile URI, http://www.w3.org/2003/g/complete/ . GRDDL-aware agents that do not implement this Note may ignore this attribute and profile URI, but SHOULD NOT generate an error if one is encountered in an XML document.

Case 1: Directly specified transformations

Given an information resource having a representation D that is an XML document having an XPath node N with root element E, if and only if the following condition holds:

the expression

/*/@*[local-name()="complete"
  and namespace-uri()=
    "http://www.w3.org/2003/g/data-view#"]

matches an attribute of E and the value of that attribute is the literal true, or http://www.w3.org/2003/g/complete/ is a metadata profile name of N (as described in the GRDDL specification, section 4),

then D directly specifies GRDDL transformations.

Given an information resource having a representation D that is an XML document having an XPath node N with root element E, if D directly specifies GRDDL transformations, then if the following steps are performed:

For all of the following transformations associated with N:
1. each transformation associated with N via the grddl:transformation attribute, as described in the GRDDL specification Adding GRDDL to well-formed XML section; and
2. each transformation associated with N via HTML links of type transformation, provided the document bears the http://www.w3.org/2003/g/data-view profile, as described in the GRDDL specification Using GRDDL with valid XHTML section.
Apply all such transformations to obtain GRDDL results.
Merge those GRDDL results.

then the resulting RDF graph is the complete GRDDL result of D.

Case 2: Namespace and profile transformations

Given an information resource having a representation D that is an XML document having an XPath node N with root element E, if D does not directly specify GRDDL transformations, then if the following steps are performed:

@@unfinished@@

For all of the following transformations associated with N:
1. each transformation associated with N via the grddl:transformation attribute, as described in the GRDDL specification Adding GRDDL to well-formed XML section; and
2. each transformation associated with N via HTML links of type transformation, provided the document bears the http://www.w3.org/2003/g/data-view profile, as described in the GRDDL specification Using GRDDL with valid XHTML section;
3. each transformation indicated by any available namespace document, as in the GRDDL for XML Namespaces section; and @@fix this clause to specify that each namespace IRI produces comlete GRDDL results@@
4. each transformation indicated by any XHTML profiles, as in the GRDDL for HTML Profiles section. @@fix this clause to specify that each profile IRI produces comlete GRDDL results@@
Apply all such transformations to obtain GRDDL results.
Merge those GRDDL results.

then the resulting RDF graph is the complete GRDDL result of D.

@@Add mention of the recursive loop case, perhaps defining the result in terms of the least fixed point.@@

Determining Complete GRDDL Results

Proposed W3C Working Group Note 18-Jun-2007

Abstract

Status of this Document

Table of Contents

Introduction

Case 1: Directly specified transformations

Case 2: Namespace and profile transformations

Appendix A: About the GRDDL complete metadata profile

Glossary

Acknowledgements

References

Change Log