| Attributes | Values |
|---|
| has container
| |
| Date Created
| - Tue, 20 Nov 2012 21:00:55 GMT
- Fri, 18 Jan 2013 15:31:20 GMT
- Fri, 26 Apr 2013 18:19:35 GMT
- Thu, 11 Jul 2013 21:22:54 GMT
- Tue, 18 Mar 2014 15:54:37 GMT
- Thu, 05 Feb 2015 21:17:51 GMT
|
| described by
| |
| seeAlso
| |
| Description
| - There are many cases when RDF data should be retrieved from remote sources only when really needed. E.g., a scheduling application may read personal calendars from personal sites of its users. Calendar data expire quickly, so there's no reason to frequently re-load them in hope that they are queried before expired. Virtuoso extends SPARQL so it is possible to download RDF resource from a given IRI, parse them and store the resulting triples in a graph, all three operations will be performed during the SPARQL query execution. The IRI of graph to store triples is usually equal to the IRI where the resource is download from, so the feature is named "IRI dereferencing" There are two different use cases for this feature. In simple case, a SPARQL query contains from clauses that enumerate graphs to process, but there are no triples in DB.DBA.RDF_QUAD that correspond to some of these graphs. The query execution starts with dereferencing of these graphs and the rest runs as usual. In more sophisticated case, the query is executed many times in a loop. Every execution produces a partial result. SPARQL processor checks for IRIs in the result such that resources with that IRIs may contain relevant data but not yet loaded into the DB.DBA.RDF_QUAD. After some iteration, the partial result is identical to the result of the previous iteration, because there's no more data to retrieve. As the last step, SPARQL processor builds the final result set.
|
| Title
| |
| Creator
| - virtuoso.docs@openlinksw.com
|
| Date
| - 2013-07-11T21:22:54Z
- 2014-03-18T15:54:37Z
|
| Title
| |
| type
| |
| content:encoded
| - There are many cases when RDF data should be retrieved from remote sources only when really needed.
E.g., a scheduling application may read personal calendars from personal sites of its users.
Calendar data expire quickly, so there's no reason to frequently re-load them in hope that they are queried before expired.
Virtuoso extends SPARQL so it is possible to download RDF resource from a given IRI, parse them and store the resulting triples in a graph, all three operations will be performed during the SPARQL query execution.
The IRI of graph to store triples is usually equal to the IRI where the resource is download from, so the feature is named "IRI dereferencing"
There are two different use cases for this feature.
In simple case, a SPARQL query contains from clauses that enumerate graphs to process, but there are no triples in DB.DBA.RDF_QUAD that correspond to some of these graphs.
The query execution starts with dereferencing of these graphs and the rest runs as usual.
In more sophisticated case, the query is executed many times in a loop.
Every execution produces a partial result.
SPARQL processor checks for IRIs in the result such that resources with that IRIs may contain relevant data but not yet loaded into the DB.DBA.RDF_QUAD.
After some iteration, the partial result is identical to the result of the previous iteration, because there's no more data to retrieve.
As the last step, SPARQL processor builds the final result set.
|
| rss:category
| |
| is topic
of | |
| is links to
of | |
| is container of
of | |
| is rdf:_13
of | |
![[RDF Data]](/fct/images/sw-rdf-blue.png)
![[cxml]](/fct/images/cxml_doc.png)
![[csv]](/fct/images/csv_doc.png)
![[text]](/fct/images/ntriples_doc.png)
![[turtle]](/fct/images/n3turtle_doc.png)
![[ld+json]](/fct/images/jsonld_doc.png)
![[rdf+json]](/fct/images/json_doc.png)
![[rdf+xml]](/fct/images/xml_doc.png)
![[atom+xml]](/fct/images/atom_doc.png)
![[html]](/fct/images/html_doc.png)