A formal versioning approach for distributed objectbases

We initially provide, in summary, a formal object-oriented model for objectbases considering (i) simple objects (classes and their instances), (ii) 2-objects (2-classes and their 2-instances) where each 2-object encapsulates a two-level-hierarchy of objects, and (iii) complex objects defined inductively from the 2-objects through a composition operation. The inheritance concept is replaced by that of a “link” between two objects. Based on the above model, we introduce and develop a formal versioning approach by defining the concepts of “core data” and “core behaviour” that together are expressed through the term “compatibility” among objects. We extend the “versioning” notion to encompass not only the instances but also the classes, and 2-classes of our formal object-oriented model and include the different “views” (modelled as objects) of an entity within the same versioning framework. We further refer to the appropriate versioning structures. We then develop a distribution strategy encompassing 2-objects and complex objects, as well as their versions, and stress the advantages (both at the design and distribution level) of this approach through an example