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== Connecting directly to virtuoso ==

Virtuoso ships with an executable called <tt>isql-vt</tt>. Just running that executable should connect you to virtuoso.

If you distribution does not provide the corresponding executable or if it doesn't work for you. Try this script -
<syntaxhighlight lang="bash">
#!/bin/bash
filename=`ps aux | grep virtuoso-t | grep -v grep | sed -e 's/.*\/tmp\///;s/ini.*/ini/'`
port=$(grep ServerPort /tmp/$filename | sed -e 's/.*=//')
exec isql-vt -S $port
</syntaxhighlight>

== Running queries directly ==

If for some reason you want to run queries directly on virtuoso, you'll need to connect to virtuoso via <tt>isql-vt</tt> and then type in the query. From 4.10, we use virtuoso's inbuilt prefix expansion, so you don't need to care about the prefixes.

=== Example ===

<syntaxhighlight lang="sql">
SQL> sparql select ?r ?name where { ?r nco:fullname ?name . };
</syntaxhighlight>

== List of tables ==

Virtuoso internally uses a relational database to store the triples. It contains the following tables -

* DB.DBA.RDF_QUAD -- The main table which contains all the statements. It contains four rows "S", "P", "O" and "G" for the subject, predicate, object and graph.
* DB.DBA.RDF_IRI
* DB.DBA.RDF_DATATYPE - Contains all the literal data types which are stored.
* DB.DBA.RDF_PREFIX
* DB.DBA.RDF_OBJ
* DB.DBA.RDF_LANGUAGE

Read http://docs.openlinksw.com/virtuoso/rdfdatarepresentation.html to properly understand how virtuoso stores the data internally.

Virtuoso has 2 main types - IRI_ID, which is the data type of the graph, subject and predicate. IRI_ID are of the form "#i25". In order to convert an integer to an IRI_ID, use the '''iri_id_from_num( int )''' function, and the '''iri_id_num( iri_id )''' to convert an IRI_ID to an integer. In order to convert an IRI_ID to its string representation use the following functions '''id_to_iri( iri_id, int )''', and '''iri_to_id( string, int )'''. The second integer option should be 0, unless you want the iri/id to be created if it doesn't exist.

== Default Indexes ==

== Common Commands ==

Apart from directly running SQL and SPARQL queries, virtuoso also provides some additional commands, which are listed over here.

=== status ===
The [http://docs.openlinksw.com/virtuoso/fn_status.html status()] function can be used to return the current running queries on virtuoso.

=== sparql_to_sql_text ===

The [http://docs.openlinksw.com/virtuoso/fn_sparql_to_sql_text.html sparql_to_sql_text()] function can be used to convert a SPARQL query directly to the SQL it would be executed as.

<syntaxhighlight lang="sql">
varchar sparql_to_sql_text
( in squery varchar );
</syntaxhighlight>

Example -
<syntaxhighlight lang="sql">
SQL> select sparql_to_sql_text('prefix nco: <http://www.semanticdesktop.org/ontologies/2007/03/22/nco#> select ?r ?name where { ?r nco:fullname ?name . }');
SPARQL_TO_SQL_TEXT
VARCHAR
_______________________________________________________________________________

SELECT __id2i ( "s_1_0-t0"."S" ) AS "r",
__ro2sq ( "s_1_0-t0"."O" ) AS "name"
FROM DB.DBA.RDF_QUAD AS "s_1_0-t0"
WHERE "s_1_0-t0"."P" = __i2idn ( __bft( 'http://www.semanticdesktop.org/ontologies/2007/03/22/nco#fullname' , 1))
OPTION (QUIETCAST)

1 Rows. -- 1 msec.
</syntaxhighlight>

It's very useful in debugging why many sparql queries are taking so long.

[[Category:Documentation]]
[[Category:Development]]
[[Category:Tutorials]]

Projects/Nepomuk/VirtuosoInternal/en - Revision history

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