1. Enabling Unambiguous GRDDL Results
David Booth Presentation to GRDDL Working Group, 20-June This document:

2. What this issue is about
Given an XML document, what RDF did the GRDDL transformation author intend to denote?
Document receiver needs to be able to determine precisely what graph the XML document was intended to denote
Critical when XML document is a serialization of RDF
GRDDL transformation says how to deserialize
12 January 2019

3. What this issue is NOT about
NOT about desired ambiguity
Transformation author may intend variable results
Can be useful sometimes -- a feature, not a bug
NOT about eliminating ambiguity that the transformation author is willing to accept
NOT about forcing the transformation author to be unambiguous
NOT about requiring the GRDDL-aware agent to actually produce the transformation author's intended results
Users may not need them all, for example
This is only about giving the transformation author the ability to be unambiguous if desired
12 January 2019

4. Kinds of unwanted ambiguity
1. Wrong results. Results contain different triples than intended.
Source of problem: ambiguous parsing/pre-processing
Proposed solutions:
Proposal 1b part 1, or
Proposal 2b part 1
2. Subsetting. User unknowingly gets a proper subset of the intended results, while believing that he/she got all of them.
Source of problem: Lack of a definition of "complete GRDDL results"
Proposed solution: WG Note
Proposal 1b parts 2, 3 & 4
12 January 2019

5. Proposal 1b part 1: Partial solution
Proposal: Change input of GRDDL transformation from XPath node tree to representation
Observations:
Reduces unwanted ambiguity problem
Permits transformation author to reduce variability in the "transformation application" step
Simple normative change
No changes to test cases
12 January 2019

6. Proposal 2b part 1: Better solution
Change input of GRDDL transformation from XPath node tree to representation; and
Specify that parsing is minimal, non-validating/me wn/
Observations:
Reduces unwanted ambiguity problem
Permits transformation author to reduce variability in the "transformation application" step
Simple normative change
No changes to test cases
12 January 2019

7. Leaving the door open to a WG Note on "Complete GRDDL Results"
Note could define "complete GRDDL results"
Based on existing sec. 7 algorithm
Not required to be implemented
Not on our critical path - could be done anytime before the WG closes
12 January 2019

8. Proposed changes to leave the door open on such a Note
a. Add one sentence to Faithful Renditions.
b. Add non-committal mention of possible WG Note.
12 January 2019

9. BACKUP SLIDES
12 January 2019

10. Variability in results -- current spec
Transformation Determination
Transformation Application
GRDDL Transf.
Select
Representation
Parse
XPath node tree
RDF
XSLT/ other
XML Doc
12 January 2019

11. Proposal 1b: Partial solution
Transformation Determination
Transformation Application
GRDDL Transf.
Select
Representation
Parse
XPath node tree
RDF
XSLT/ other
XML Doc
Reduces problem in "transformation application" step
But not in "transformation determination" step
12 January 2019

12. Proposal 2b: Full(?) solution
Transformation Determination
Transformation Application
GRDDL Transf.
Select
Representation
Parse
XPath node tree
RDF
XSLT/ other
XML Doc
Limits parsing to minimum, non-validating
12 January 2019