1. A computer-system-implemented method for representing a compound relationship in a graph stored in a graph database, the method comprising: defining the compound relationship based on two or more predicates associated with two or more edges between two or more nodes in the graph; generating, in the graph, a hub node that corresponds to the compound relationship and that has an identifier that is hidden from users of the graph; adding an edge associated with an attribute predicate between the hub node and a node that includes an attribute of one of the two or more nodes; and when a cardinality of the attribute predicate is equal to one, replacing the attribute with an updated attribute of the one of the two or more nodes.