A Data Definition Facility Based on A Value-Oriented Storage Model

摘要

A data definition facility is presented that provides a consistent description of both primitive and user data. It is based on a value-oriented storage model which carefully distinguishes between values and objects. It is values that are typed in this model, and operations of the type work explicitly on the values. Objects are accessible only via reference values. Objects are described via descriptors called templates, which ultimately yield reference type values. Operations, both primitive and user-defined, are part of a “machine interface,” and all executable language constructs can ultimately be defined as explicit operations of the interface. Importantly, these operations must respect the typing constraints imposed by both the primitive types and the user extensions. The interactions of definition facility, storage model, and execution model are illustrated via a series of examples in which commonly user data constructs are defined.