Copyright © 2007 Hewlett-Packard Development Company, LP. All Rights Reserved.
This document describes SPARQL/Update (nicknamed "SPARUL"), an update language for RDF graphs. It uses a syntax derived form SPARQL. Update operations are performed on a collection of graphs in a Graph Store. Operations are provided to change existing RDF graphs as well as create and remove graphs with the Graph Store.
This document does not discuss the SPARQL/Update protocol [SPARQL/Update/Protocol].
Published for discussion.
SPARQL/Update is a language to express updates to an RDF store. It is intended to be a standard mechanism by which updates to a remote RDF Store can be described, communicated and stored. SPARQL/Update is a companion language to SPARQL and is envisaged to be used in conjunction with SPARQL query language and protocol. The reuse of the SPARQL syntax, in both style and detail, reduces the learning curve for developers and reduces implementation costs.
SPARQL/Update provides the following facilities:
This document also describes the use HTTP for the transfer of update operations.
See also:
SPARQL/Update is not:
Language forms are show as:
INSERT { template } [ WHERE { pattern } ]
[] indicates an optional part of the syntax. [] are
still used for blank nodes in SPARQL requests.
Italics indicate an item is some syntax element
derived from SPARQL.
Examples are shown as:
PREFIX dc: <http://purl.org/dc/elements/1.1/>
INSERT { <http://example/egbook3> dc:title "This is an example title" }
This section gives some example snippets in the proposed SPARQL/Update language that would be used to update a remote RDF store.
(a) Adding some triples to a graph. The snippet describes two RDF triples to be inserted into the default graph of the RDF store.
PREFIX dc: <http://purl.org/dc/elements/1.1/>
INSERT
{ <http://example/book3> dc:title "A new book" ;
dc:creator "A.N.Other" .
}
(b) This SPARQL/Update request contains a triple to be deleted and a triple to be added (used here to correct a book title). The requested modification is effected in the named graph identified by the URI http://example/bookStore.
PREFIX dc: <http://purl.org/dc/elements/1.1/>
MODIFY GRAPH <http://example/bookStore>
DELETE
{ <http://example/book3> dc:title "Fundamentals of Compiler Desing" }
INSERT
{ <http://example/book3> dc:title "Fundamentals of Compiler Design" }
(c) The example below has a request to delete all records of old books (with date before year 2000)
PREFIX dc: <http://purl.org/dc/elements/1.1/>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
DELETE
{ ?book ?p ?v }
WHERE
{ ?book dc:date ?date .
FILTER ( ?date < "2000-01-01T00:00:00"^^xsd:dateTime )
}
(d) This snippet copies records from one named graph to another named graph based on a pattern
PREFIX dc: <http://purl.org/dc/elements/1.1/>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
INSERT INTO GRAPH <http://example/bookStore2>
{ ?book ?p ?v }
WHERE
{ GRAPH <http://example/bookStore>
{ ?book dc:date ?date .
FILTER ( ?date < "2000-01-01T00:00:00"^^xsd:dateTime )
?book ?p ?v
} }
(e) An example to move records from one named graph to another named graph based on a pattern
PREFIX dc: <http://purl.org/dc/elements/1.1/>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
INSERT INTO GRAPH <http://example/bookStore2>
{ ?book ?p ?v }
WHERE
{ GRAPH <http://example/bookStore>
{ ?book dc:date ?date .
FILTER ( ?date < "2000-01-01T00:00:00"^^xsd:dateTime )
}
}
DELETE FROM GRAPH <http://example/bookStore>
{ ?book ?p ?v }
WHERE
{ GRAPH <http://example/bookStore>
{ ?book dc:date ?date .
FILTER ( ?date < "2000-01-01T00:00:00"^^xsd:dateTime )
}
}
A Graph Store is a repository of RDF graphs managed by a single service. Like an RDF Dataset operated on by SPARQL, a Graph Store has zero or one unnamed graphs and zero or more named graphs. Additionally, graphs can be added or deleted.
In the simple case, where there is one default graph and no named graphs, SPARQL/Update is a language for update of a single graph.
If an update service is managing some graph store, then there is no presumption that this exactly corresponds to any RDF dataset offered by some query service. The dataset of the query service may be formed from graphs managed by the update service but the dataset offered by the query can be a subset of the graphs in the update service dataset and the names of those graphs may be different. The composition of the RDF dataset may also change.
SPARQL/Update requests are a sequence of operations. Each request should be treated atomically by a SPARQL/Update service.
If two different update services are managing their respective graph stores share a common graph, there is no presumption that the updates done through one service would be propagated to the other. The behaviour of these services with respect to each other is implementation dependent. It is recommended that such deployment scenarios are completely avoided. An implementation must target SPARQL queries on updated graphs if the SPARQL and SPARUL end points are the same.
SPARQL/Update supports two categories of update operations on a Graph Store:
Graph update operations change existing graphs in the Graph Store but do not create or delete them.
The fundamental operation of a graph update is MODIFY. There are two restricted forms for INSERT and DELETE of triples; both are special cases of the MODIFY operation. A modify operation consists of a group of triples to be deleted and a group of triples to be added. The specification of the triples can be based on a query pattern.
The LOAD operation reads the contents of one graph into another.
The CLEAR operation removes all the triples in a graph.
# UPDATE outline syntax : general form:
MODIFY [ GRAPH <uri> ]
DELETE { template }
INSERT { template }
[ WHERE { pattern } ]
The template and pattern forms are as
defined in
SPARQL for construct
templates and graph patterns.
The deletion of the triples happens before the insertion. The pattern in
WHERE
clause is evaluated only once, before the delete part of the operation is
performed. The overall
processing model is that the pattern is executed, the results used to
instantiate the DELETE template, the deletes performed, the results used again to
instantiate the INSERT template, and the inserts performed.
The pattern is evaluated as in a SPARQL query SELECT * WHERE { pattern }
and all the named variables are made available to the INSERT template
and the DELETE template for defining the triples to be inserted or
deleted.
The GRAPH <uri> clause names the graph in the graph store to be
updated; if omitted, the MODIFY applies to the unnamed graph.
If the operation is on a graph that does not exist, an error is generated. Graphs are not created by the graph update operations. The graph management operations have to be used to create new graphs.
The DELETE operation is similar to the MODIFY operation with
an empty INSERT template. The graph
URI, if present, must be a valid named graph in the Graph Store.
DELETE [ FROM GRAPH <uri> ]* { template } [ WHERE { pattern } ]
# Equivalent to
MODIFY [ GRAPH <uri> ]*
DELETE { template }
INSERT { }
[ WHERE { pattern } ]
The INSERT operation is similar to the MODIFY operation with
an empty DELETE template. The graph
URI, if present, must be a valid named graph in the Graph Store. The
CREATE graph management operator should be used to create a new named
graph in the Graph Store.
INSERT [ INTO GRAPH <uri> ]* { template } [ WHERE { pattern } ]
#Equivalent to
MODIFY [ GRAPH <uri> ]*
DELETE { }
INSERT { template }
[ WHERE { pattern } ]
The LOAD operation copies all the triples of a remote graph into the
specified graph, or if not specified, the default graph of the Graph Store.
LOAD <remoteURI> [ INTO GRAPH <uri> ]
The CLEAR operations removes all the triples of the specified graph
or if not specified, the default graph of the Graph Store. This operation does not remove the graph from the Graph Store.
# Remove all triples. CLEAR [ GRAPH <uri> ]
It has the same effect as:
# Remove all triples.
DELETE [ GRAPH <uri> ] { ?s ?p ?o } WHERE { ?s ?p ?o }
but is a clearer expression of empting a graph.
Graph management operations create and destroy named graphs in the Graph Store.
The default graph in a Graph Store always exists.
CREATE [ SILENT ] GRAPH <uri>
This operation creates a new named graph with a name as specified by the URI. After the successful completion of this operation, the new named graph is available for any further graph update operations with MODIFY, INSERT and DELETE operators.
The SPARQL/Update service generates an error if the graph referred by the
URI already exists unless the keyword SILENT
is present when no error is generated and execution of the sequence of
SPARQL/Update operations continues.
DROP [ SILENT ] GRAPH <uri>
This operation removes the specified named graph from the Graph Store associated with the SPARQL/Update service endpoint. After successful completion of this operation, the named graph is no more available for further graph update operations.
The SPARQL/Update service, by default, is expected to generate an error if the
specified named graph does not exist. If
SILENT is present, this error is ignored and execution of a
sequence of SPARQL/Update operations continues.
Rules from rule Prologue are taken from the SPARQL grammar.