“…The conventional KG completion (link prediction) task can be viewed as a complex query with a single triplet pattern without logical operators, e.g., Citizen(USA, V ), which we also denote as a projection query. To tackle complex queries on incomplete knowledge graphs, query embedding methods are proposed to execute logic operations in the latent space, including variants that employ geometric [15,23,38], probabilistic [24,9], neural-symbolic [26,8,5], neural [21,4], and GNN [11,3] approaches for learning entity, relation, and query representations.…”