An apparatus comprising: an encoder adapted to encode, for each of a plurality of knowledge graph (112, 200, 300) entities, wherein the knowledge graph entities comprise graph nodes, a digital attribute value associated with each knowledge graph entity into at least one primitive; a correlator adapted to correlate the at least one primitive associated with a first knowledge graph entity of a first knowledge graph with the at least one primitive associated with a second knowledge graph entity of a second knowledge graph to generate a matched pair to obtain a composite knowledge graph (112, 200, 300, 400); an interface adapted to receive a digital request for information, and respond to said digital request for information with at least one digital attribute value of said matched pair (810, 915, 1010, 1030, 1420a), the correlator adapted to correlate the at least one first knowledge graph entity with the at least one second knowledge graph (112, 114, 122, 200, 300) entity by being adapted to perform the following steps: computing a similarity metric for each of a plurality of candidate pairs, each candidate pair comprising a first knowledge graph entity and a second knowledge graph (112, 114, 122, 200, 300) entity; and selecting said at least one matched pair (810, 915, 1010, 1030, 1420a) from the plurality of candidate pairs based on the computed similarity metrics, the correlator computing the similarity metric for each candidate pair by: identifying at least one extended pair (810, 820, 830, 840, 915, 1010, 1030) associated with a primitive, said at least one extended pair being coupled directly or indirectly to said candidate pair; for each of said at least one extended pair (810, 820, 830, 840, 915, 1010, 1030), computing an initial similarity metric; and generating the similarity metric as the weighted sum of initial similarity metrics of all said at least one extended pair (810, 820, 830, 840, 915, 1010, 1030) coupled to said candidate pair, the weight comprising the probability of landing at the candidate pair starting from the respective extended pair. an encoder adapted to encode, for each of a plurality of knowledge graph (112, 200, 300) entities, wherein the knowledge graph entities comprise graph nodes, a digital attribute value associated with each knowledge graph entity into at least one primitive; a correlator adapted to correlate the at least one primitive associated with a first knowledge graph entity of a first knowledge graph with the at least one primitive associated with a second knowledge graph entity of a second knowledge graph to generate a matched pair to obtain a composite knowledge graph (112, 200, 300, 400); an interface adapted to receive a digital request for information, and respond to said digital request for information with at least one digital attribute value of said matched pair (810, 915, 1010, 1030, 1420a), the correlator adapted to correlate the at least one first knowledge graph entity with the at least one second knowledge graph (112, 114, 122, 200, 300) entity by being adapted to perform the following steps: computing a similarity metric for each of a plurality of candidate pairs, each candidate pair comprising a first knowledge graph entity and a second knowledge graph (112, 114, 122, 200, 300) entity; and selecting said at least one matched pair (810, 915, 1010, 1030, 1420a) from the plurality of candidate pairs based on the computed similarity metrics, computing a similarity metric for each of a plurality of candidate pairs, each candidate pair comprising a first knowledge graph entity and a second knowledge graph (112, 114, 122, 200, 300) entity; and selecting said at least one matched pair (810, 915, 1010, 1030, 1420a) from the plurality of candidate pairs based on the computed similarity metrics, the correlator computing the similarity metric for each candidate pair by: identifying at least one extended pair (810, 820, 830, 840, 915, 1010, 1030) associated with a primitive, said at least one extended pair being coupled directly or indirectly to said candidate pair; for each of said at least one extended pair (810, 820, 830, 840, 915, 1010, 1030), computing an initial similarity metric; and generating the similarity metric as the weighted sum of initial similarity metrics of all said at least one extended pair (810, 820, 830, 840, 915, 1010, 1030) coupled to said candidate pair, the weight comprising the probability of landing at the candidate pair starting from the respective extended pair. identifying at least one extended pair (810, 820, 830, 840, 915, 1010, 1030) associated with a primitive, said at least one extended pair being coupled directly or indirectly to said candidate pair; for each of said at least one extended pair (810, 820, 830, 840, 915, 1010, 1030), computing an initial similarity metric; and generating the similarity metric as the weighted sum of initial similarity metrics of all said at least one extended pair (810, 820, 830, 840, 915, 1010, 1030) coupled to said candidate pair, the weight comprising the probability of landing at the candidate pair starting from the respective extended pair.