1. A computer implemented method comprising: a. optimizing a query, wherein a query result is reached from a query node by following one or more join paths in a schema graph to find a Y value for a specified value X in the presence of the join paths, wherein the schema graph comprises a field X and a field Y; b. evaluating the schema graph identifying the join paths between the field X, and the field Y, and the specified value X; c. providing individual data paths that instantiate the join paths wherein at least one of the individual data paths includes an intra-table edge including a key field; d. evaluating and scoring each data path with respect to specified integrity constraints for measuring aggregate data quality wherein said evaluating and scoring includes assigning a weighting to the intra-table edge wherein the assigned weighting is indicative of an extent to which the key field in the intra-table edge deviates from an exact key; e. computing scores using the scored data paths with X values and derived Y values, wherein the scores are agglomerated for yielding overall scores for matching or pairing X values to Y values; and f. finding the Y values reachable from the specified value X when using the multiple join paths.