14. The apparatus of claim 10 , wherein the ontology schema path acquisition unit searches the ontology schema path database and obtains an ontology schema path, in which the start class and the end class corresponding to each pair of classes are connected to the start or end, for each pair of classes, respectively.
10. An apparatus of searching for an instance path based on an ontology schema, the apparatus comprising: a processor; a memory coupled to the processor; an ontology schema database in which relationship information between classes is stored; an ontology instance database in which relationship information between instances is stored; an ontology schema path database in which ontology schema paths connected between two or more classes with respect to all classes stored in the ontology schema database are stored; a user interface unit which receives two or more keywords from a user; an instance pair generation unit which obtains instances of the input keywords from the ontology instance database and generating pairs of instances; a class pair extraction unit which extracts a pair of classes corresponding to each of the generated pairs of instances from the ontology instance database, respectively; an ontology schema path acquisition unit which obtains an ontology schema path connected between two or more classes with respect to each of the pairs of classes from the ontology schema path database, respectively; and an instance path search unit which replaces start and end classes with corresponding first and second instances in the ontology schema path and searches for an instance path connected between the first instance and the second instance, respectively, wherein the instance path refers to a path in which instances are connected via one or more relationships, wherein the instance path search unit comprises: a join schedule generation module which replaces the start and end classes with corresponding first and second instances in the ontology schema path, divides the ontology schema path into halves, and generates a first join schedule including the first instance and a second join schedule including the second instance; an instance search module which, if there is a class connected to the first instance or second instance based on the first or second join schedule, extracts at least one instance connected to the first instance or second instance from instances included in the connected class; and an instance path generation module which generates instance paths in which the extracted instances are connected between the first instance and the second instance.