1. A system including: a data storage system storing a specification for each of multiple sources, each specification including information identifying one or more data elements of the corresponding source; and a data processing system that communicates with the data storage system configured to process data elements of the sources, including: identify terms and associated descriptions in a first source, for each term in the first source, identify a first predetermined number of terms in a second source that are most similar to the term in the first source, and identify a second predetermined number of term descriptions that are the most similar to the term description in the first source, and for each term in the first source, apply one or more rules to evaluate quality of matches between the term in the first source and the terms in the second source, in which each rule evaluates a similarity between the term of the first source and the term in the second source, and evaluate a similarity between the term description of the first source and the term description of the second source.