- 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>
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 UTC