Graph patterns

Graph patterns — Collections of triple patterns, sub-graph patterns with operators.

Synopsis

typedef             rasqal_graph_pattern;
int                 rasqal_graph_pattern_add_constraint (rasqal_graph_pattern *gp,
                                                         rasqal_expression *expr);
int                 rasqal_graph_pattern_add_sub_graph_pattern
                                                        (rasqal_graph_pattern *graph_pattern,
                                                         rasqal_graph_pattern *sub_graph_pattern);
rasqal_expression*  rasqal_graph_pattern_get_constraint (rasqal_graph_pattern *gp,
                                                         int idx);
raptor_sequence*    rasqal_graph_pattern_get_constraint_sequence
                                                        (rasqal_graph_pattern *gp);
int                 rasqal_graph_pattern_get_index      (rasqal_graph_pattern *gp);
rasqal_graph_pattern_operator rasqal_graph_pattern_get_operator
                                                        (rasqal_graph_pattern *graph_pattern);
rasqal_graph_pattern* rasqal_graph_pattern_get_sub_graph_pattern
                                                        (rasqal_graph_pattern *graph_pattern,
                                                         int idx);
raptor_sequence*    rasqal_graph_pattern_get_sub_graph_pattern_sequence
                                                        (rasqal_graph_pattern *graph_pattern);
rasqal_triple*      rasqal_graph_pattern_get_triple     (rasqal_graph_pattern *graph_pattern,
                                                         int idx);
enum                rasqal_graph_pattern_operator;
const char*         rasqal_graph_pattern_operator_as_string
                                                        (rasqal_graph_pattern_operator op);
void                rasqal_graph_pattern_print          (rasqal_graph_pattern *gp,
                                                         FILE *fh);
int                 (*rasqal_graph_pattern_visit_fn)    (rasqal_query *query,
                                                         rasqal_graph_pattern *gp,
                                                         void *user_data);
int                 rasqal_graph_pattern_visit          (rasqal_query *query,
                                                         rasqal_graph_pattern *gp,
                                                         rasqal_graph_pattern_visit_fn fn,
                                                         void *user_data);

Description

Graph patterns form a a tree structure that build a rasqal_query top-level graph pattern (see rasqal_query_get_query_graph_pattern()) which may have sub-graph patterns. Graph patterns at the leaf of the tree operate over triple patterns (rasqal_triple) matching the RDF triples in the data sources for RASQAL_GRAPH_PATTERN_OPERATOR_BASIC or RASQAL_GRAPH_PATTERN_OPERATOR_OPTIONAL. Other graph patterns operators operate over sub graph patterns and group them, union them or apply a GRAPH matching keyword (RASQAL_GRAPH_PATTERN_OPERATOR_GRAPH).

Details

rasqal_graph_pattern

rasqal_graph_pattern* graph_pattern;

Rasqal graph pattern class.

rasqal_graph_pattern_add_constraint ()

int                 rasqal_graph_pattern_add_constraint (rasqal_graph_pattern *gp,
                                                         rasqal_expression *expr);

Add a constraint expression to the graph_pattern.

gp :

 rasqal_graph_pattern query object

expr :

 rasqal_expression expr - ownership taken

Returns :

 non-0 on failure

rasqal_graph_pattern_add_sub_graph_pattern ()

int                 rasqal_graph_pattern_add_sub_graph_pattern
                                                        (rasqal_graph_pattern *graph_pattern,
                                                         rasqal_graph_pattern *sub_graph_pattern);

Add a sub graph pattern to a graph pattern.

graph_pattern :

 graph pattern to add to

sub_graph_pattern :

 graph pattern to add inside

Returns :

 non-0 on failure

rasqal_graph_pattern_get_constraint ()

rasqal_expression*  rasqal_graph_pattern_get_constraint (rasqal_graph_pattern *gp,
                                                         int idx);

Get a constraint in the sequence of constraint expressions in the query.

gp :

 rasqal_graph_pattern query object

idx :

 index into the sequence (0 or larger)

Returns :

 a rasqal_expression pointer or NULL if out of the sequence range

rasqal_graph_pattern_get_constraint_sequence ()

raptor_sequence*    rasqal_graph_pattern_get_constraint_sequence
                                                        (rasqal_graph_pattern *gp);

Get the sequence of constraints expressions in the query.

gp :

 rasqal_graph_pattern object

Returns :

 a raptor_sequence of rasqal_expression pointers.

rasqal_graph_pattern_get_index ()

int                 rasqal_graph_pattern_get_index      (rasqal_graph_pattern *gp);

Get the graph pattern absolute index in the array of graph patterns.

The graph pattern index is assigned when rasqal_query_prepare() is run on a query containing a graph pattern.

gp :

 rasqal_graph_pattern graph pattern

Returns :

 index or <0 if no index has been assigned yet

rasqal_graph_pattern_get_operator ()

rasqal_graph_pattern_operator rasqal_graph_pattern_get_operator
                                                        (rasqal_graph_pattern *graph_pattern);

Get the graph pattern operator .

The operator for the given graph pattern. See also rasqal_graph_pattern_operator_as_string().

graph_pattern :

 rasqal_graph_pattern graph pattern object

Returns :

 graph pattern operator

rasqal_graph_pattern_get_sub_graph_pattern ()

rasqal_graph_pattern* rasqal_graph_pattern_get_sub_graph_pattern
                                                        (rasqal_graph_pattern *graph_pattern,
                                                         int idx);

Get a sub-graph pattern inside a graph pattern.

graph_pattern :

 rasqal_graph_pattern graph pattern object

idx :

 index into the sequence of sub graph_patterns in the graph pattern

Returns :

 rasqal_graph_pattern or NULL if out of range

rasqal_graph_pattern_get_sub_graph_pattern_sequence ()

raptor_sequence*    rasqal_graph_pattern_get_sub_graph_pattern_sequence
                                                        (rasqal_graph_pattern *graph_pattern);

Get the sequence of graph patterns inside a graph pattern .

graph_pattern :

 rasqal_graph_pattern graph pattern object

Returns :

 a raptor_sequence of rasqal_graph_pattern pointers.

rasqal_graph_pattern_get_triple ()

rasqal_triple*      rasqal_graph_pattern_get_triple     (rasqal_graph_pattern *graph_pattern,
                                                         int idx);

Get a triple inside a graph pattern.

graph_pattern :

 rasqal_graph_pattern graph pattern object

idx :

 index into the sequence of triples in the graph pattern

Returns :

 rasqal_triple or NULL if out of range

enum rasqal_graph_pattern_operator

typedef enum {
  RASQAL_GRAPH_PATTERN_OPERATOR_UNKNOWN   = 0,
  RASQAL_GRAPH_PATTERN_OPERATOR_BASIC     = 1,
  RASQAL_GRAPH_PATTERN_OPERATOR_OPTIONAL  = 2,
  RASQAL_GRAPH_PATTERN_OPERATOR_UNION     = 3,
  RASQAL_GRAPH_PATTERN_OPERATOR_GROUP     = 4,
  RASQAL_GRAPH_PATTERN_OPERATOR_GRAPH     = 5,

  RASQAL_GRAPH_PATTERN_OPERATOR_LAST=RASQAL_GRAPH_PATTERN_OPERATOR_GRAPH
} rasqal_graph_pattern_operator;

Graph pattern operators

RASQAL_GRAPH_PATTERN_OPERATOR_UNKNOWN

 Internal.

RASQAL_GRAPH_PATTERN_OPERATOR_BASIC

 Just triple patterns and constraints.

RASQAL_GRAPH_PATTERN_OPERATOR_OPTIONAL

 Set of graph patterns (ANDed) and constraints.

RASQAL_GRAPH_PATTERN_OPERATOR_UNION

 Set of graph patterns (UNIONed) and constraints.

RASQAL_GRAPH_PATTERN_OPERATOR_GROUP

 Set of graph patterns (ANDed) and constraints.

RASQAL_GRAPH_PATTERN_OPERATOR_GRAPH

 A graph term + a graph pattern and constraints.

RASQAL_GRAPH_PATTERN_OPERATOR_LAST

 Internal.

rasqal_graph_pattern_operator_as_string ()

const char*         rasqal_graph_pattern_operator_as_string
                                                        (rasqal_graph_pattern_operator op);

Get a string for the query verb.

op :

 the rasqal_graph_pattern_operator verb of the query

Returns :

 pointer to a shared string label for the query verb

rasqal_graph_pattern_print ()

void                rasqal_graph_pattern_print          (rasqal_graph_pattern *gp,
                                                         FILE *fh);

Print a rasqal_graph_pattern in a debug format.

The print debug format may change in any release.

gp :

 the rasqal_graph_pattern object

fh :

 the FILE* handle to print to

rasqal_graph_pattern_visit_fn ()

int                 (*rasqal_graph_pattern_visit_fn)    (rasqal_query *query,
                                                         rasqal_graph_pattern *gp,
                                                         void *user_data);

User function to visit an graph_pattern and operate on it with rasqal_graph_pattern_visit() or rasqal_query_graph_pattern_visit()

query :

 rasqal_query containing the graph pattern

gp :

 current graph_pattern

user_data :

 user data passed in

Returns :

 0 to truncate the visit

rasqal_graph_pattern_visit ()

int                 rasqal_graph_pattern_visit          (rasqal_query *query,
                                                         rasqal_graph_pattern *gp,
                                                         rasqal_graph_pattern_visit_fn fn,
                                                         void *user_data);

Visit a user function over a rasqal_graph_pattern

If the user function fn returns 0, the visit is truncated.

query :

 rasqal_query to operate on

gp :

 rasqal_graph_pattern graph pattern

fn :

 pointer to function to apply that takes user data and graph pattern parameters

user_data :

 user data for applied function

Returns :

 0 if the visit was truncated.
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