1. A computer-implemented method for processing a graph query in connection with at least one processor of a computer system, wherein the graph query serves for retrieving data items from a data source by indicating at least a source node representing one or more source item types, a target node representing one or more target item types, and a plurality of edges between the source node and the target node, wherein each edge comprises one or more relation conditions, wherein each relation condition defines a mapping between items of one of the source item types and items of one of the target item types, the method comprising: (a) selecting a first edge of the plurality of edges; (b) traversing the selected first edge from the source node to the target node in accordance with the one or more relation conditions of the first edge to produce an intermediate set of result items, wherein the intermediate set of result items comprises the items of the data source which belong to the at least one target item type and which fulfill the corresponding one or more relation conditions; (c) selecting a further edge of the plurality of edges; (d) traversing the selected further edge from the target node to the source node in accordance with the one or more relation conditions of the selected further edge, and deleting items from the intermediate set of result items produced in (b) which do not fulfill the corresponding one or more relation conditions; (e) repeating (c) and (d) for each further edge of the plurality of edges; and (f) returning the intermediate set of result items as the result of the graph query processed by the at least one processor.