Access and query task force status at f2f1
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Access and Query Task Force Status at F2F1. Simon Miles. Starting point. The WG agreed to use the report of the W3C incubator group on provenance as a starting point for discussing access and query of provenance This refers to:

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Access and Query Task Force Status at F2F1

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Access and Query Task ForceStatus at F2F1

Simon Miles


Starting point

  • The WG agreed to use the report of the W3C incubator group on provenance as a starting point for discussing access and query of provenance

  • This refers to:

    • Passing provenance of resource state representations via HTTP by value, by reference, or mixed

    • Embedding provenance or references to it in HTTP messages, or in HTML, RDF or other representations supporting embedded metadata

    • Negotiation over the kind, granularity and form of provenance they receive


Scope for F2F1

  • For the first F2F, we solicited proposals to address two provenance access questions

  • Because they were inspired by the XG report, they made particular assumptions about the form of access information

  • The proposals did not all share the same initial assumptions, and so the questions were generalised to reflect this


Scoping questions (generalised)

  • Given information regarding where to access data on the provenance of a resource state representation, what form does that information take and how do we obtain the provenance data?

  • How can a browser find the information on where to access provenance data, referred to above, for an HTML document that was downloaded, so that its provenance may be retrieved?


Multiple URIs

  • These questions were originally expressed with the assumption that the information took the form of an identifier for the representation, I, plus a location from which to retrieve it, L. The second question then assumed that I and L are embedded in the HTML document.

  • In fact, the proposals referred to multiple URIs:

    • R: The URI of the resource

    • I: The URI of the resource state representation

    • L:The URI of some provenance service

    • P:The URI of some provenance information


Summary of proposals for Q1

  • Use HTTP Link in response to accessing the resource (R) to give a URI for a thing’s provenance (P)

  • Use HTTP to GET the provenance of a thing, by deferencing a URI for that provenance (P)

  • Use HTTP to GET the provenance of a thing (I) from a provenance service (L)

  • Use a SPARQL endpoint as as provenance service (L)

  • A RESTful provenance service (L) where the thing’s (I) metadata expresses how to parameterise access


Summary of proposals for Q2

  • Use HTML Link to give a URI for a page’s provenance (P)

  • Use an HTML Profile for provenance metadata (I + L)

  • User POWDER metadata to give a default provenance service (L)

  • Use HTML Meta or microdata to give provenance access info (I + L)


Suggested guiding principles

  • Graham proposed some principles, which I try to paraphrase below:

    • Aim to use simple solutions unless the requirement for more complex ones is presented

    • Justify why any complexity is introduced

    • Work by iterating over a draft of the final deliverable


Suggested decision points (1)

  • There may be data regarding the provenance of a thing accessible from multiple sources.

  • The information required to obtain access to some provenance of a thing may be supplied in many different ways, and we do not aim to enumerate them all.

  • The WG effort will concern how the provider of a thing can supply information required to obtain access to some provenance of that thing (which may, as a side effect, include recommendations on how others can do the same).


Suggested decision points (2)

  • Regarding some provenance data obtained from dereferencing a provenance URI, calling a provenance service, or some other means. Which of the following is true?

    • (a) It is apparent from the data itself what single thing it describes the provenance of.

    • (b) Provenance data documents a set of things and how they are related by past occurrences, so to extract the provenance of any one thing requires knowing how it is identified in the data.

    • (c) Something else.

  • Regarding some provenance data obtained from dereferencing a provenance URI, calling a provenance service, or some other means. Which of the following is true?

    • (a) To meet the standard, it should be immutable.

    • (b) It can change over time without restriction.

    • (c) To meet the standard, there are particular ways in which it should not change, e.g. any one account should remain as it was


Suggested decision points (3)

  • We should use HTTP negotiation to determine the format of provenance information accessed, rather than specifying another mechanism

  • We should use queries (i.e. SPARQL) to determine the content of provenance information accessed, e.g. granularity, rather than specifying another mechanism


Future work and further issues

  • The TF needs to determine how it decides between competing proposals

  • This may mean

    • agreeing general points as above

    • adopting simple solutions before considering complex ones

    • justifying by reference to use cases

  • Other issues raised by the group:

    • Guidance for publishers of provenance

    • Provenance moving from one location to another

    • Specifying multiple provenance sources in one embedding

    • Ensuring data and provenance can be kept within the same file


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