Data Graphs

## Data Graphs Data Graphs — RDF graph sources for triples. |

## Synopsis

                        rasqal_data_graph;
    rasqal_data_graph * rasqal_new_data_graph_from_data_graph
                                                            (rasqal_data_graph *dg);
    rasqal_data_graph * rasqal_new_data_graph_from_iostream (rasqal_world *world,
                                                             raptor_iostream *iostr,
                                                             raptor_uri *base_uri,
                                                             raptor_uri *name_uri,
                                                             unsigned int flags,
                                                             const char *format_type,
                                                             const char *format_name,
                                                             raptor_uri *format_uri);
    rasqal_data_graph * rasqal_new_data_graph_from_uri      (rasqal_world *world,
                                                             raptor_uri *uri,
                                                             raptor_uri *name_uri,
                                                             unsigned int flags,
                                                             const char *format_type,
                                                             const char *format_name,
                                                             raptor_uri *format_uri);
    void                rasqal_free_data_graph              (rasqal_data_graph *dg);
    enum                rasqal_data_graph_flags;
    int                 rasqal_data_graph_print             (rasqal_data_graph *dg,
                                                             FILE *fh);

## Description

Data graphs are used in the query to describe RDF graphs that can be used to query against. The graphs can be used either with raptor_uri to name the graph, or without a name. The query language determines which graphs are used in the query.

## Details

### rasqal_data_graph

    typedef struct {
      rasqal_world* world;
      raptor_uri* uri;
      raptor_uri* name_uri;
      unsigned int flags;
      char* format_type;
      char* format_name;
      raptor_uri* format_uri;
      raptor_iostream* iostr;
      raptor_uri* base_uri;
      int usage;
    } rasqal_data_graph;

A source of RDF data for querying.

If `iostr` is present, the graph can be constructed by parsing the iostream and using `base_uri` as a base uri. Otherwise the graph can be constructed from the graph at URI `uri`.

In either case the `name_uri` is the graph name as long as `flags` is `RASQAL_DATA_GRAPH_NAMED`

rasqal_world *`world`; | rasqal_world object
raptor_uri *`uri`; | source URI
raptor_uri *`name_uri`; | name of graph for `RASQAL_DATA_GRAPH_NAMED`
unsigned int `flags`; | `RASQAL_DATA_GRAPH_NAMED` or `RASQAL_DATA_GRAPH_BACKGROUND`
char *`format_type`; | MIME Type of data format at `uri` (or NULL)
char *`format_name`; | Raptor parser Name of data format at `uri` (or NULL)
raptor_uri *`format_uri`; | URI of data format at `uri` (or NULL)
raptor_iostream *`iostr`; | Raptor iostream for content, overriding `uri` if present (or NULL)
raptor_uri *`base_uri`; | base URI for reading from iostream
int `usage`; | usage count of this object

### rasqal_new_data_graph_from_data_graph ()

    rasqal_data_graph * rasqal_new_data_graph_from_data_graph
                                                            (rasqal_data_graph *dg);

Copy Constructor - create a new rasqal_data_graph object from an existing rasqal_data_graph object.

`dg` : | rasqal_data_graph object to copy or NULL
Returns : | a new rasqal_data_graph object or NULL if `dg` was NULL.

### rasqal_new_data_graph_from_iostream ()

    rasqal_data_graph * rasqal_new_data_graph_from_iostream (rasqal_world *world,
                                                             raptor_iostream *iostr,
                                                             raptor_uri *base_uri,
                                                             raptor_uri *name_uri,
                                                             unsigned int flags,
                                                             const char *format_type,
                                                             const char *format_name,
                                                             raptor_uri *format_uri);

Constructor - create a new rasqal_data_graph from iostream content

The `name_uri` is used when the flags are `RASQAL_DATA_GRAPH_NAMED`.

The `base_uri` is used to provide the Raptor parser a base URI. If a base URI is required but none is given, the parsing will fail and the query that uses this data source will fail.

`world` : | rasqal_world object
`iostr` : | source graph format iostream
`base_uri` : | base URI for iostream content
`name_uri` : | name of graph (or NULL)
`flags` : | `RASQAL_DATA_GRAPH_NAMED` or `RASQAL_DATA_GRAPH_BACKGROUND`
`format_type` : | MIME Type of data format at `uri` (or NULL)
`format_name` : | Raptor parser Name of data format at `uri` (or NULL)
`format_uri` : | URI of data format at `uri` (or NULL)
Returns : | a new rasqal_data_graph or NULL on failure.

### rasqal_new_data_graph_from_uri ()

    rasqal_data_graph * rasqal_new_data_graph_from_uri      (rasqal_world *world,
                                                             raptor_uri *uri,
                                                             raptor_uri *name_uri,
                                                             unsigned int flags,
                                                             const char *format_type,
                                                             const char *format_name,
                                                             raptor_uri *format_uri);

Constructor - create a new rasqal_data_graph.

The name_uri is only used when the flags are `RASQAL_DATA_GRAPH_NAMED`.

`world` : | rasqal_world object
`uri` : | source URI
`name_uri` : | name of graph (or NULL)
`flags` : | `RASQAL_DATA_GRAPH_NAMED` or `RASQAL_DATA_GRAPH_BACKGROUND`
`format_type` : | MIME Type of data format at `uri` (or NULL)
`format_name` : | Raptor parser Name of data format at `uri` (or NULL)
`format_uri` : | URI of data format at `uri` (or NULL)
Returns : | a new rasqal_data_graph or NULL on failure.

### rasqal_free_data_graph ()

    void                rasqal_free_data_graph              (rasqal_data_graph *dg);

Destructor - destroy a rasqal_data_graph object.

`dg` : | rasqal_data_graph object

### enum rasqal_data_graph_flags

    typedef enum {
      RASQAL_DATA_GRAPH_NONE  = 0,
      RASQAL_DATA_GRAPH_NAMED = 1,
      RASQAL_DATA_GRAPH_BACKGROUND = 2
    } rasqal_data_graph_flags;

Flags for the type of rasqal_data_graph.

These are used by `rasqal_new_data_graph_from_uri()` and `rasqal_new_data_graph_from_iostream()`. See rasqal_data_graph.

`RASQAL_DATA_GRAPH_NONE` | Internal.
`RASQAL_DATA_GRAPH_NAMED` | Graphs with a source and name.
`RASQAL_DATA_GRAPH_BACKGROUND` | Graphs with a source only.

### rasqal_data_graph_print ()

    int                 rasqal_data_graph_print             (rasqal_data_graph *dg,
                                                             FILE *fh);

Print a Rasqal data graph in a debug format.

The print debug format may change in any release.

`dg` : | rasqal_data_graph object
`fh` : | the FILE* handle to print to
Returns : | non-0 on failure