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---+ Virtuoso Redland RDF Storage Provider
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---++ What is Redland
[[http://librdf.org][Redland]] is a set of free software 'C' libraries that provide support for the
Resource Description Framework (RDF), providing modular, object-based libraries, and APIs for manipulating
the RDF graph, triples, URIs, and Literals. Redland includes several high-level language APIs providing
RDF manipulation and storage, and requires the [[http://librdf.org/raptor/][Raptor]] RDF parser and
[[http://librdf.org/rasqal/][Rasqal]] RDF syntax and query library for its use.
---++ What is the Virtuoso Redland Provider
The Virtuoso Redland RDF Provider is an implementation of the Storage API, Model, and Query interfaces
of the Redland framework for RDF. This provider enables the execution of queries via the Redland Rasqal
query engine or via Virtuoso query engine directly against the Virtuoso Quad store. The Virtuoso Redland
Provider uses ODBC as the data access mechanism for communicating with the Virtuoso Quad Store and therefore
requires the Virtuoso ODBC Driver be installed on the Redland client and a suitable ODBC DSN be configured
for connecting to the target Virtuoso Quad Store instance. The provider has been tested against the
[[http://download.librdf.org/source/][Redland 1.0.8]] version available for download at the time of writing.
---+++ Fig 1: Redland Component Stack
As indicated in the diagram above, the Virtuoso Provider can be used to execute RDF queries either directly
against the Virtuoso graph storage module (which supports the [[http://dbpedia.org/resource/SPARQL][SPARQL]],
[[http://dbpedia.org/resource/SPARUL][SPARUL]], and
[[http://virtuoso.openlinksw.com/dataspace/dav/wiki/Main/VOSArticleBISPARQL2][SPARQL-BI]] query languages)
or via the Rasqal query engine built into Redland (which supports only the SPARQL query language). The
query handler is specified by the query; use "vsparql" for Virtuoso, or the default "sparql" for Redland,
as indicated in the sample queries below:
rdfproc -r xml -t "user='dba',password='dba',dsn='Demo'" gr query sparql - "SELECT * WHERE { ?s ?p ?o }" ;; via Redland Rasqal engine
rdfproc -r xml -t "user='dba',password='dba',dsn='Demo'" gr query vsparql - "SELECT * WHERE { ?s ?p ?o }" ;; direct to Virtuoso storage module
The Virtuoso Provider uses the [[http://virtuoso.openlinksw.com/dataspace/dav/wiki/Main/VOSSQL2RDF][SPASQL]]
query language for querying the remote Virtuoso QUAD store.
---++ Setup
---+++ Required files
The Virtuoso Redland Provider has been integrated into the Redland RDF Framework and submitted to the open source
project to become part of the standard distribution available for [[http://librdf.org/INSTALL.html][download]].
---+++ Compling Redland with Virtuoso storage support
1 [[http://svn.librdf.org/][Download Redland]] from the svn repository.
1 Use the following additional configure options to enable support for Virtuoso storage:
--with-virtuoso(=yes|no) Enable Virtuoso RDF store
(default=auto)
--with-iodbc(=DIR) Select iODBC support
DIR is the iODBC base install directory
(default=/usr/local)
--with-unixodbc(=DIR) Select UnixODBC support
DIR is the UnixODBC base install directory
(default=/usr/local)
--with-datadirect(=DIR) Select DataDirect support
DIR is the DataDirect base install directory
(default=/usr/local)
--with-odbc-inc=DIR Specify custom ODBC include directory
(default=/usr/local/include)
--with-odbc-lib=DIR Specify custom ODBC lib directory
(default=/usr/local/lib)
* The --with-virtuoso option is auto-enabled if a valid ODBC Driver
Manager (iODBC, UnixODBC, or DataDirect) or include and lib
directories for required ODBC header files and libraries are discovered via the suitable
setting for one or more of the other ODBC related options above.
* Assuming [[http://www.iodbc.org/][iODBC]] is installed, the following command can
be used to enable Virtuoso storage support to be configured for compilation into
your Redland build:
./configure --with-iodbc=/usr/local/iODBC
1 Run make to compile the Redland libraries and sudo make install
to install in the default /usr/local location
1 Test compilation with the utils/rdfproc test utility. This test will use
the default hashes storage.
rdfproc test parse http://planetrdf.com/guide/rss.rdf
rdfproc test print
rdfproc test serialize ntriples
1 Ensure you have [[http://virtuoso.openlinksw.com/download/][the Virtuoso ODBC Driver]]
installed, and [[http://docs.openlinksw.com/virtuoso/odbcimplementation/][a valid ODBC
DSN called "Local Virtuoso"]] configured for your target Virtuoso Server.
1 Set the following environment variable:
export RDFPROC_STORAGE_TYPE=virtuoso ;; Enable Virtuoso Storage
export ODBCINI=/odbc.ini ;; Enable ODBC DSN to be located
export LD_LIBRARY_PATH=/usr/local/lib:$LD_LIBRARY_PATH ;; May be required to enable Redland libraries to be located
1 Test Virtuoso storage with the provided utils/vtest test program:
$ utils/vtest
1: Remove all triples in context
**PASSED**: removed context triples from the graph
2: Add triples to context
**PASSED**: add triple to context
3: Print all triples in context
[[
{[aa], [bb], [cc]} with context [http://red]
{[aa], [bb1], [cc]} with context [http://red]
{[aa], [a2], "cc"} with context [http://red]
{[aa], [a2], (cc)} with context [http://red]
{[mm], [nn], "Some long literal with language@en"} with context [http://red]
{[oo], [pp], "12345^^"} with context [http://red]
]]
**PASSED**:
4: Count of triples in context
**PASSED**: graph has 6 triples
5: Exec: ARC aa bb
Matched node: [cc]
**PASSED**:
6: Exec: ARCS aa cc
Matched node: [bb] with context [http://red]
Matched node: [bb1] with context [http://red]
: matching nodes: 2
**PASSED**:
7: Exec: ARCS-IN cc
Matched arc: [bb] with context [http://red]
Matched arc: [bb1] with context [http://red]
**PASSED**: matching arcs: 2
8: Exec: ARCS-OUT aa
Matched arc: [bb] with context [http://red]
Matched arc: [bb1] with context [http://red]
Matched arc: [a2] with context [http://red]
Matched arc: [a2] with context [http://red]
**PASSED**: matching arcs: 4
9: Exec: CONTAINS aa bb1 cc
**PASSED**: the graph contains the triple
10: Exec: FIND aa - -
Matched triple: {[aa], [bb], [cc]} with context [http://red]
Matched triple: {[aa], [bb1], [cc]} with context [http://red]
Matched triple: {[aa], [a2], "cc"} with context [http://red]
Matched triple: {[aa], [a2], (cc)} with context [http://red]
**PASSED**: matching triples: 4
11: Exec: HAS-ARC-IN cc bb
**PASSED**: the graph contains the arc
12: Exec: HAS-ARC-OUT aa bb
**PASSED**: the graph contains the arc
13: Exec: SOURCE aa cc
Matched node: [aa]
**PASSED**:
14: Exec: SOURCES bb cc
Matched node: [aa] with context [http://red]
: matching nodes: 1
**PASSED**:
15: Exec: TARGET aa bb
Matched node: [cc]
**PASSED**:
16: Exec: TARGETS aa bb
Matched node: [cc] with context [http://red]
: matching nodes: 1
**PASSED**:
17: Exec: REMOVE aa bb1 cc
**PASSED**: removed triple from the graph
18: Exec: QUERY "CONSTRUCT {?s ?p ?o} FROM WHERE {?s ?p ?o}"
Matched triple: {[aa], [a2], "cc"}
Matched triple: {[oo], [pp], "12345^^"}
Matched triple: {[aa], [a2], (cc)}
Matched triple: {[aa], [bb], [cc]}
Matched triple: {[mm], [nn], "Some long literal with language@en"}
**PASSED**: matching triples: 5
19: Exec1: QUERY_AS_BINDINGS "SELECT * WHERE {graph { ?s ?p ?o }}"
**: Formatting query result as 'xml':
aa
bb
cc
aa
a2
cc
aa
a2
cc
mm
nn
Some long literal with language@en
oo
pp
12345^^<http://www.w3.org/2001/XMLSchema#int>
**PASSED**:
20: Exec2: QUERY_AS_BINDINGS "SELECT * WHERE {graph { ?s ?p ?o }}"
: Query returned bindings results:
result: [s=[aa], p=[bb], o=[cc]]
result: [s=[aa], p=[a2], o=cc]
result: [s=[aa], p=[a2], o=(cc)]
result: [s=[mm], p=[nn], o=Some long literal with language@en]
result: [s=[oo], p=[pp], o=12345^^]
: Query returned 5 results
**PASSED**:
=============================================
PASSED: 20 FAILED: 0
---+++ Connection Attributes
The Virtuoso Redland Provider has the following connection attributes available for use:
* *dsn* - ODBC datasource name
* *user* - user name of database server
* *password* - password of database server
* *host* - hostname:portno of the database server
* *charset* - database charset to use
NOTE: Take care exposing the password as, for example, program arguments or environment
variables. The rdfproc utility can help with this by reading the password from standard
input. Inside programs, one way to prevent storing the password in a string is to construct a Redland
hash of the storage options such as via librdf_hash_from_string and
use librdf_new_storage_with_options to create a storage. The
rdfproc utility source code demonstrates this.
The storage name parameter given to the storage constructor librdf_new_storage
is used inside the Virtuoso store to allow multiple stores inside one Virtuoso database instance, as
parametrized with the options above.
This store always provides contexts; the Boolean storage option contexts is not checked.
Examples:
/* A new Virtuoso store */
storage=librdf_new_storage(world, "virtuoso", "db1",
"dsn='Local Virtuoso',user='demo',password='demo'");
/* A different, existing Virtuoso store in the same database as above */
storage=librdf_new_storage(world, "virtuoso", "db2",
"dsn='Local Virtuoso',user='demo',password='demo'");
/* An existing Virtuoso store on a different database server */
storage=librdf_new_storage(world, "virtuoso", "http://red3",
"dsn='Remote Virtuoso',user='demo',password='demo'");
/* Opening with an options hash */
options=librdf_new_hash(world, NULL);
librdf_hash_from_string(options,
"dsn='Local Virtuoso',user='demo'");
librdf_hash_put_strings(options, "password", user_password);
storage=librdf_new_storage_with_options(world, "virtuoso", "http://red3", options);
---++ Related
* [[VirtJenaProvider][Virtuoso Jena RDF Storage Provider]]
* [[VirtSesame2Provider][Virtuoso Sesame RDF Storage Provider]]
* [[VirtRDFDriverRedland][Virtuoso Redland RDF Storage Provider]]
* [[VirtRDFInsert][RDF Insert Methods in Virtuoso]]
* [[VirtBulkRDFLoader][Guide for Bulk Loading of RDF Source Files into one or more Graph IRIs]]
* [[VOSBuild][Virtuoso Installation Guide]]
* [[http://librdf.org/docs/api/redland-storage.html][RedLand Triple Store]]
* [[http://librdf.org/docs/api/redland-storage-modules.html][RedLand Storage Modules]]
CategoryRDF CategoryOpenSource CategoryVirtuoso CategoryVOS CategoryNativeRDFProviders CategoryDocumentation
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