A data enrichment system may include an attribute relevance module to measure relevance of an attribute to a data object to be enriched. The data object may include the attribute including a known or an unknown value. An output value confidence module may calculate a confidence of an output value of a source used for enrichment of the data object. The output value may represent the known and/or unknown values of the attribute. The system may use the measured relevance of the attribute and the calculated confidence of the output value to determine assignment of the known or unknown values to the attribute.