A three-level object-based model

The three fundamental areas of functionality in an object-based system are the creation, encapsulation and access of related data. Parallel to these areas of functionality we may identify three levels of data: data which exists as long as an object does, data which exists for the length of a procedure invocation and data which exists for the length of a process's use of an object. A new object model is proposed based on these levels of functionality and data. Objects are divided into three distinct categories (called modules, instances and handles). Each category has an explicitly defined set of functions (which are already implicitly existent in most object-based systems), including creation of one of the levels of data. Every object in a system belongs to one (and only one) category. Under this model, users should be able to more readily understand the use of any given object, as its category would be easily identifiable.<
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