Querying

Querying — RDF query languages and execution.

Synopsis

typedef             librdf_query;
typedef             librdf_query_factory;
void                librdf_query_register_factory       (librdf_world *world,
                                                         const char *name,
                                                         unsigned char *uri_string,
                                                         void (factorylibrdf_query_factory*) ());
librdf_query*       librdf_new_query                    (librdf_world *world,
                                                         const char *name,
                                                         librdf_uri *uri,
                                                         unsigned char *query_string,
                                                         librdf_uri *base_uri);
librdf_query*       librdf_new_query_from_query         (librdf_query *old_query);
librdf_query*       librdf_new_query_from_factory       (librdf_world *world,
                                                         librdf_query_factory *factory,
                                                         const char *name,
                                                         librdf_uri *uri,
                                                         unsigned char *query_string,
                                                         librdf_uri *base_uri);
void                librdf_free_query                   (librdf_query *query);
librdf_query_results* librdf_query_execute              (librdf_query *query,
                                                         librdf_model *model);
int                 librdf_query_get_limit              (librdf_query *query);
int                 librdf_query_set_limit              (librdf_query *query,
                                                         int limit);
int                 librdf_query_get_offset             (librdf_query *query);
int                 librdf_query_set_offset             (librdf_query *query,
                                                         int offset);

Description

Provides classes to create query objects and to execute them over an RDF graph (librdf_model) returning a librdf_query_results Query result limits and offsets can be set.

Details

librdf_query

typedef struct librdf_query_s librdf_query;

Redland query class.

librdf_query_factory

typedef struct librdf_query_factory_s librdf_query_factory;

Redland query factory class.

librdf_query_register_factory ()

void                librdf_query_register_factory       (librdf_world *world,
                                                         const char *name,
                                                         unsigned char *uri_string,
                                                         void (factorylibrdf_query_factory*) ());

Register a query factory.

world :

 redland world object

name :

 the query language name

uri_string :

 the query language URI string (or NULL if none)

factory :

 pointer to function to call to register the factory

librdf_new_query ()

librdf_query*       librdf_new_query                    (librdf_world *world,
                                                         const char *name,
                                                         librdf_uri *uri,
                                                         unsigned char *query_string,
                                                         librdf_uri *base_uri);

Constructor - create a new librdf_query object.

world :

 redland world object

name :

 the name identifying the query language

uri :

 the URI identifying the query language (or NULL)

query_string :

 the query string

base_uri :

 the base URI of the query string (or NULL)

Returns :

 a new librdf_query object or NULL on failure

librdf_new_query_from_query ()

librdf_query*       librdf_new_query_from_query         (librdf_query *old_query);

Should create a new query in the same context as the existing one as appropriate.

old_query :

 the existing query librdf_query to use

Returns :

 a new librdf_query object or NULL on failure

librdf_new_query_from_factory ()

librdf_query*       librdf_new_query_from_factory       (librdf_world *world,
                                                         librdf_query_factory *factory,
                                                         const char *name,
                                                         librdf_uri *uri,
                                                         unsigned char *query_string,
                                                         librdf_uri *base_uri);

Constructor - create a new librdf_query object.

world :

 redland world object

factory :

 the factory to use to construct the query

name :

 query language name

uri :

 query language URI (or NULL)

query_string :

 the query string

base_uri :

 base URI of the query string (or NULL)

Returns :

 a new librdf_query object or NULL on failure

librdf_free_query ()

void                librdf_free_query                   (librdf_query *query);

Destructor - destroy a librdf_query object.

query :

 librdf_query object

librdf_query_execute ()

librdf_query_results* librdf_query_execute              (librdf_query *query,
                                                         librdf_model *model);

Run the query on a model.

Runs the query against the (previously registered) model and returns a librdf_query_results for the result objects.

query :

 librdf_query object

model :

 model to operate query on

Returns :

 librdf_query_results or NULL on failure

librdf_query_get_limit ()

int                 librdf_query_get_limit              (librdf_query *query);

Get the query-specified limit on results.

This is the limit given in the query on the number of results allowed.

query :

 librdf_query query object

Returns :

 integer >=0 if a limit is given, otherwise <0

librdf_query_set_limit ()

int                 librdf_query_set_limit              (librdf_query *query,
                                                         int limit);

Set the query-specified limit on results.

This is the limit given in the query on the number of results allowed.

query :

 librdf_query query object

limit :

 the limit on results, >=0 to set a limit, <0 to have no limit

Returns :

 non-0 on failure

librdf_query_get_offset ()

int                 librdf_query_get_offset             (librdf_query *query);

Get the query-specified offset on results.

This is the offset given in the query on the number of results allowed.

query :

 librdf_query query object

Returns :

 integer >=0 if a offset is given, otherwise <0

librdf_query_set_offset ()

int                 librdf_query_set_offset             (librdf_query *query,
                                                         int offset);

Set the query-specified offset on results.

This is the offset given in the query on the number of results allowed.

query :

 librdf_query query object

offset :

 offset for results, >=0 to set an offset, <0 to have no offset

Returns :

 non-0 on failure
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