public MetadataGraph addEdge(MetadataGraphVertex vFrom, MetadataGraphVertex vTo, MetadataGraphEdge e)
            throws MetadataResolutionException {
        checkVertex(vFrom);
        checkVertex(vTo);

        checkVertices();

        checkEdge(e);
        checkEdges();

        e.setSource(vFrom);
        e.setTarget(vTo);