1. A data enrichment system comprising: an attribute relevance module, executed by a processor, to measure relevance of an attribute to a data object to be enriched, the data object including the attribute including one of a known and an unknown value; and an output value confidence module to calculate a confidence of a source based on utility of an output value of the source used for enrichment of the data object, the output value representing at least one of the known and unknown values of the attribute, wherein the confidence of the source is increased based on corroboration of the output value with output values of a plurality of sources and decreased based on ambiguity in the output value if a plurality of output values are generated by the source, and wherein the system uses the measured relevance of the attribute and the calculated confidence of the source to determine assignment of the unknown value to the attribute.