Synopsis
#include <liblod.h>
int
lod_instance_exists
(LODINSTANCE *instance
);
Description
lod_instance_exists
checks that the subject of
an instance exists in the associated context's model.
A liblod instance is a simple kind of query for
any triples whose subject matches the URI provided to
lod_resolve
. There are various circumstances
by which lod_resolve
can successfully return an
instance, but that the subject of the instance doesn't actually
exist in the data held by the model.
Because an instance is a query against a model, a call to
lod_instance_exists
may have different results
at different times. For example, it might initially return zero (false),
but following a new call to lod_resolve
(or
manually adding triples to the associated librdf
model), the next call might return non-zero (true).
Return value
If the subject of the instance does not exist in the context,
lod_instance_exists
returns zero.
Otherwise, lod_instance_exists
returns
a positive integer.