Abstract: A data services layer is disclosed which maintains a dictionary of conceptual information and physical information about the data. Machine-readable requests to access the data are in a form related to a conceptual organization of the data, and is not specific to a physical organization of the data. A machine-readable query to obtain a subset of the data is produced by referencing the dictionary of conceptual and physical information about the data. The conceptual information is obtained from an object-relational-model of the data, and the physical information indicates how the data is organized on the data storage medium. Requests are written in a conceptual query language (CQL) which substantially uses terms belonging to or derived from a natural language. CQL includes terms in the classes of names and concepts, and wherein name terms are used to describe objects in the object-relational-model of the data, and concept terms are used to specify the data subset desired.