We describe a constructive approach to the specification of data types. The primary motivation for this approach, which is referred to as the Logical Structure Operation Specification (LSOS), is to highlight certain aspects of a data type, and to possibly suggest one or more implementations for the data type.A key feature of the LSOS is its flexibility, which permits a wide variety of specifications for a data type.This allows the specifier of a data type to communicate to the user any view or perspective which was taken in developing the data type.