Jay Banerjee

Semantics and implementation of schema evolution in object-oriented databases

Object-oriented programming is well-suited to such data-intensive application domains as CAD/CAM, AI, and OIS (office information systems) with multimedia documents. At MCC we have built a prototype object-oriented database system, called ORION. It adds persistence and sharability to objects created and manipulated in applications implemented in an object-oriented programming environment. One of the important requirements of these applications is schema evolution, that is, the ability to dynamically make a wide variety of changes to the database schema. In this paper, following a brief review of the object-oriented data model that we support in ORION, we establish a framework for supporting schema evolution, define the semantics of schema evolution, and discuss its implementation.

Queries in object-oriented databases

A query under an object-oriented data model exhibits characteristics which one finds in a relational query and those which clearly separate it from a relational query. The differences in turn have interesting impacts on the complexity of and strategy for query evaluation in object-oriented databases. The authors develop a model of a query under an object-oriented data model, and analyze the fundamental differences in the semantics of queries in object-oriented databases and relational databases.<<ETX>>

Clustering a DAG for CAD databases

A DAG (direct acyclic graph) is an important data structure which requires efficient support in CAD (computer-aided design) databases. It typically arise from the design hierarchy, which describes complex designs in terms of subdesigns. A study is made of the properties of the three types of clustered sequences of nodes for hierarchies and DAGs, and algorithms are developed for generating the clustered sequences, retrieving the descendants of a given node, and inserting new nodes into existing clustered sequences of nodes which preserve their clustering properties. The performance of the clustering sequences is compared. >

Object-oriented database support for CAD

Abstract ORION is a prototype object-oriented database system built in the Advanced Computer Technology (ACT) Program at MCC. It is intended to support the data management needs of applications in such domains as computer-aided design, artificial intelligence, and office information systems. The paper describes features of ORION which have been implemented specifically to support CAD environments. These include dynamic schema evolution, version control and change notification, and transaction management.

Operations and implementation of complex objects

Many applications in the CAD/CAM and AI domains require the capability to define and manipulate a structured collection of records as a single logical entity, called a complex object. A complex object is the unit of sharing among many configurations of higher level entities. In this paper, we present a model of complex object and define a set of meaningful operations, both basic and advanced, on a single complex object and on a configuration of complex objects. We then present a set of requirements for storage subsystems that support complex objects. We also describe our implementation of complex objects and operations on a single complex object; and provide a detailed performance analysis which establishes the merit of complex objects. Finally, we propose storage techniques for supporting advanced operations on a configuration of complex objects.

Supporting VLSI geometry operations in a database system

VLSI layout systems perform various operations on design data describing the layouts of geometries (rectangles) on different mask layers. In this paper, we identify a basic set of such operations and show a formulation of these operations in terms of expressions of predicates that are suitable for processing by a database system. We then describe the operations and properties of a 4-D (four-dimensional) tree structure for efficiently supporting these operations. We also provide a qualitative analysis of the time complexity of the data structure, which compares favorably against various existing proposals.

Enhancing the object-oriented concepts for database support

In this paper, we elaborate on three major enhancements to the conventional object-oriented data model, namely, schema evolution, composite objects, and versions. Schema evolution is the ability to dynamically make changes to the class definitions and the structure of the class lattice. Composite objects are recursive collections of exclusive components that are treated as units of storage, retrieval, and integrity enforcement. Versions are variations of the same object that are related by the history of their derivation. These additional features are strongly motivated by data management requirements of object-oriented applications from the AI, CAD/CAM, and OIS (office information systems with multimedia documents) domains. An object-oriented data model, with these enhancements, has been incorporated into ORION, a prototype database system developed at MCC as a vehicle of research into object-oriented databases.