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 an output value of a 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 system uses the measured relevance of the attribute and the calculated confidence of the output value to determine assignment of one of the known and unknown values to the attribute.