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Main uses seen for redland contexts for provenance

From: Dave Beckett <dave.beckett@bristol.ac.uk>
Date: Tue, 24 Aug 2004 14:38:52 +0100
To: DAWG public list <public-rdf-dawg@w3.org>
Message-Id: <20040824143852.116c02ac@hoth.ilrt.bris.ac.uk>

This message is addressing:
  ACTION DaveB: explain the main uses seen for redland contexts with
  respect to the provenance.


Background

Redland originally provided a triple store with APIs for accessing
it.  However as users were starting to develop with it especially for
handing multiple graphs retrieved from the web, it became clear that
better support was needed for managing aggregations, along with a way
to query for the source of a particular triple when it appeared in a
("triples matching" style) query.  Source meaning usually the URI the
content was originally at.

Redland Contexts[1] were developed which allows assigning of any URI
(Literal, bnode) to a triple when it is stored which allows recording
of some source URI but also allows more flexibility.

Typically in a resource retrieval operation, you fetch a URI along
with some other contextual information such as HTTP Accept:, Cookies,
HTTP ETags and need also to record the date of the retrieval for
caching, any errors that occurred and maybe also some indication of
when to re-try the failure.  Then the content (say RDF/XML) is parsed
and the triples that result are recorded along with the retrieval
information.  This is explained more in [2].

So Redland does more than just BRQL SOURCE (which is sufficient for
the most part) but also provides a way to record addtional provenance
and to retrieve it.


Uses Seen

* Recording the resource URI (source URI) which had been retrieved to
  give a representation, giving triples

* Returning the source URI for triples given in a query

* Recording additional contextual information on the retrieval
  operation including the source URI but other properties like HTTP
  headers and date/time, retries.

(I also outline some other potential uses in [1] and [2] but they
have not been seen used).

Dave

[1] Redland Contexts
http://www.redland.opensource.ac.uk/notes/contexts.html


[2] SWAD-Europe Deliverable 12.4.1: Large Scale Resource Discovery
and Presentation Demonstrator
  http://www.w3.org/2001/sw/Europe/reports/large_scale_demo/
Received on Tuesday, 24 August 2004 13:39:59 GMT

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