Description

lod_resolve attempts to resolve a Linked Open Data URI: that is, perform one or more HTTP requests in order to obtain data describing the subject identified by uri.

In contrast to lod_fetch (which will attempt a network fetch regardless of the existing contents of the context’s model), and lod_locate (which will never attempt a network fetch), the behaviour of lod_resolve is conditional depending upon whether uri is the subject of a triple within the context’s model.

If such a triple is present, lod_resolve behaves as lod_locate, returning an instance whose subject is uri.

If no such triple could be found, lod_resolve behaves as though lod_fetch had been called instead.

Return value

Upon success, lod_resolve returns a new LODINSTANCE, which should be later freed using lod_instance_destroy.

If an error occurs, or uri was not a subject of any triple in the data after the fetch completes, lod_resolve returns NULL.

Use lod_error to determine whether an error occurred, or whether the subject does not exist in the data. If an error does occur, you can use lod_errmsg to obtain a description of the error condition.

Example

LODCONTEXT *ctx;
LODINSTANCE *inst;

ctx = lod_create();
inst = lod_resolve(ctx, "http://www.dbpedialite.org/things/22308#id");
if(!inst)
{
	if(lod_error(ctx))
	{
		/* An error occurred */
	}
	else
	{
		/* No error, but the subject wasn't present */
	}
}
else
{
	/* Triples found */
	lod_instance_destroy(inst);
}
lod_destroy(ctx);

See also

liblod, lod_create, lod_error, lod_errmsg, lod_locate, lod_fetch, lod_instance_destroy, lod_instance_stream, librdf_parser_create.