Support for unusual applications such as computer-aided design data has been of increasing interest to database system architects. In this survey, we concentrate on one aspect of such support, namely, version modeling. By this, we mean the concepts suitable for structuring a database of complex engineering artifacts that evolve across multiple representations and over time and the operations through which such artifact descriptions are created and modified. There have been many proposals for new models and mechanisms to support such concepts within database data models in general and engineering data models in particular; here we not only describe such proposals; we also unify them. We do not propose yet another model but provide a common terminology and collection of mechanisms that underlie any approach for representing engineering design information in a database. The key remaining challenge is to construct a single framework, based on these mechanisms, which can be tailored for the needs of a given version environment.

Toward a unified framework for version modeling in engineering databases

We describe the results of developing the GemStone object-oriented database server, which supports a model of objects similar to that of Smalltalk-80. We begin with a summary of the goals and requirements for the system: an extensible data model that captures behavioral semantics, no artificial bounds on the number or size of database objects, database amenities (concurrency, transactions, recovery, associative access, authorization) and an interactive development environment. Object-oriented languages, Smalltalk in particular, answer some of these requirements. We discuss satisfying the remaining requirements in an object oriented context, and report briefly on the status of the development efforts. This paper is directed at an audience familiar with object-oriented languages and their implementation, but perhaps unacquainted with the difficulties and techniques of database system development. It updates the original report on the project [CM], and expands upon a more recent article [MDP].

Development of an object-oriented DBMS

Megaprogramming is a technology for programming with large modules called megamodules that capture the functionality of services provided by large organizations like banks, airline reservation systems, and city transportation systems. Megamodules are internally homogeneous, independently maintained software systems managed by a community with its own terminology, goals, knowledge, and programming traditions. Each megamodule describes its externally accessible data structures and operations and has an internally consistent behavior. The concepts, terminology, and interpretation paradigm of a megamodule is called its ontology.

Toward megaprogramming

We describe a semantic object-oriented data model for representing how a complex design database evolves over time. Structural relationships, introduced by the data management system, are imposed on the objects created by existing CAD tools. The relationships supported by the model are (1) version histories, (2) time-varying configurations, and (3) equivalences among objects of different types. We describe mechanisms for (1) identifying current versions, (2) supporting dynamic configuration binding, and (3) verifying equivalence relationships. The data model is being implemented in a Version Server, under development at the University of California, Berkeley.

Version modeling concepts for computer-aided design databases

A design data management system bridges the gap between design tools and database systems, creating an integrated tool environment. Although design databases have long been of interest, they have been largely ignored within the context of the new tools. Our purpose is to describe what design data management is and how it can integrate design tools. Our discussion focuses on unique data management requirements of design systems and conventional database facilities and their shortcomings for supporting design data. We also present the architecture of a prototype design management system in which designs are organized into a richly interconnected data structure, using an object data model. The structures of that system's storage, recovery, concurrency control, and design validation subsystems are also described as is a "browser" for interactively viewing design data.

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Katz

Papers

Managing the chip design database