1. A computer-implemented method for storing graph data representing a workflow of a business process, the method comprising: generating the workflow of the business process; generating a graph having a plurality of nodes and connecting edges, wherein contents of the workflow is stored in the form of graphs; generating a graph data having a predicate and arguments corresponding to the nodes; implementing a B-tree as a set of tables including a predicate table and arguments tables; storing the predicate in the predicate table of the B-tree; storing the arguments in arguments tables of the B-tree; storing relations between the arguments in a relations table of the B-tree; generating a link to the relations table of the B-tree; generating links to the arguments table of the B-tree; storing the link to the relations table of the B-tree and the links to the arguments tables of the B-tree in the predicate table of the B-tree so as to indicate a connection between the relations B-tree and the arguments B-trees, wherein relations between the predicate and the arguments are determined by the edges of the graph; determining, in response to a request for a graph item from a requestor, a set of arguments and a relation connected by the predicate table of the B-tree; and returning the graph item to the requestor.