Triples

## Triples Triples — Triple pattern or RDF triple. |

## Synopsis

                rasqal_triple;
    enum        rasqal_triple_flags;
    rasqal_triple* rasqal_new_triple            (rasqal_literal *subject,
                                                 rasqal_literal *predicate,
                                                 rasqal_literal *object);
    rasqal_triple* rasqal_new_triple_from_triple
                                                (rasqal_triple *t);
    void        rasqal_free_triple              (rasqal_triple *t);
    rasqal_literal* rasqal_triple_get_origin    (rasqal_triple *t);
    enum        rasqal_triple_parts;
    void        rasqal_triple_print             (rasqal_triple *t,
                                                 FILE *fh);
    void        rasqal_triple_set_origin        (rasqal_triple *t,
                                                 rasqal_literal *l);

## Description

An object for a triple pattern or an RDF triple in a query. It contains the three parts of an RDF triple - subject, predicate, object as well as origin for matching triples in some graph (such as with the SPARQL `GRAPH`).

## Details

### rasqal_triple

    typedef struct {
      rasqal_literal* subject;
      rasqal_literal* predicate;
      rasqal_literal* object;
      rasqal_literal* origin;
      unsigned int flags;
    } rasqal_triple;

A triple pattern or RDF triple.

This is used as a triple pattern in queries and an RDF triple when generating RDF triples such as with SPARQL CONSTRUCT.

rasqal_literal *`subject`; | Triple subject.
rasqal_literal *`predicate`; | Triple predicate.
rasqal_literal *`object`; | Triple object.
rasqal_literal *`origin`; | Triple origin.
unsigned int `flags`; | Or of enum rasqal_triple_flags bits.

### enum rasqal_triple_flags

    typedef enum {

      /* Not used - was only used internally in the execution engine */
      RASQAL_TRIPLE_FLAGS_EXACT=1,

      /* Not used - this is now a property of a graph pattern */
      RASQAL_TRIPLE_FLAGS_OPTIONAL=2,

      RASQAL_TRIPLE_FLAGS_LAST=RASQAL_TRIPLE_FLAGS_OPTIONAL
    } rasqal_triple_flags;

Flags for triple patterns.

`RASQAL_TRIPLE_FLAGS_EXACT` | Not used.
`RASQAL_TRIPLE_FLAGS_OPTIONAL` | Not used.
`RASQAL_TRIPLE_FLAGS_LAST` | Internal.

### rasqal_new_triple ()

    rasqal_triple* rasqal_new_triple            (rasqal_literal *subject,
                                                 rasqal_literal *predicate,
                                                 rasqal_literal *object);

Constructor - create a new rasqal_triple triple or triple pattern.

The triple origin can be set with `rasqal_triple_set_origin()`.

`subject` : | Triple subject.
`predicate` : | Triple predicate.
`object` : | Triple object.
Returns : | a new rasqal_triple or NULL on failure.

### rasqal_new_triple_from_triple ()

    rasqal_triple* rasqal_new_triple_from_triple
                                                (rasqal_triple *t);

Copy constructor - create a new rasqal_triple from an existing one.

`t` : | Triple to copy.
Returns : | a new rasqal_triple or NULL on failure.

### rasqal_free_triple ()

    void        rasqal_free_triple              (rasqal_triple *t);

Destructor - destroy a rasqal_triple object.

`t` : | rasqal_triple object.

### rasqal_triple_get_origin ()

    rasqal_literal* rasqal_triple_get_origin    (rasqal_triple *t);

Get the origin field of a rasqal_triple.

`t` : | The triple object.
Returns : | The triple origin or NULL.

### enum rasqal_triple_parts

    typedef enum {
      RASQAL_TRIPLE_SUBJECT  = 1,
      RASQAL_TRIPLE_PREDICATE= 2,
      RASQAL_TRIPLE_OBJECT   = 4,
      RASQAL_TRIPLE_ORIGIN   = 8
    } rasqal_triple_parts;

Flags for parts of a triple.

`RASQAL_TRIPLE_SUBJECT` | Subject present in a triple.
`RASQAL_TRIPLE_PREDICATE` | Predicate present in a triple.
`RASQAL_TRIPLE_OBJECT` | Object present in a triple.
`RASQAL_TRIPLE_ORIGIN` | Origin present in a triple.

### rasqal_triple_print ()

    void        rasqal_triple_print             (rasqal_triple *t,
                                                 FILE *fh);

Print a Rasqal triple in a debug format.

The print debug format may change in any release.

`t` : | rasqal_triple object.
`fh` : | The FILE* handle to print to.

### rasqal_triple_set_origin ()

    void        rasqal_triple_set_origin        (rasqal_triple *t,
                                                 rasqal_literal *l);

Set the origin field of a rasqal_triple.

`t` : | The triple object.
`l` : | The rasqal_literal object to set as origin.