Using the theory of terminology for special languages, we investigate data, their representations, the semantics of data, and allowed computations. These three components for understanding data are related, and terminology supplies the link. The key insight, using terminology, is that a datum is represented by a signifier that stands for a certain kind of concept. The concept is part of the semantics. The kind of concept describes the computation. The paper contains a thorough exploration. A rich descriptive framework is the result, and this framework may significantly alter the way users find statistical data. Currently, users usually must know which agency has the data they are looking for. Reducing or eliminating this dependence will greatly increase the ease and flexibility with which users find US federal statistical data.