JUNE 1991, Volume 14, No. 2 a quarterly bulletin of the IEEE Computer Society technical committee on Data Engineering CONTENTS Letter from the Issue Editor 1 Rakesh Agrawal The Two Facets of Object—Oriented Data Models 3 Serge Abiteboul and ParisC. Kanellakis Theoretical Foundations for OODB’s a Personal Perspective 8 Catriel Been A First—Order Formalization of Object—Oriented Languages 13 Michael Kifer On Data Restructuring and Merging with Object Identity 18 Richard Hull, Surjatini Widjojo, Dave Wile, and Masatoshi Yoshikawa Data Structures and Data Types for Object—Oriented Databases 23 Vat Breazu—Tannen, Peter Buneman, and Atsushi Ohori Foundations of the 02 Database System 28 C. Lecluse and P. Richard Updating the Schema of an Object—Oriented Database 33 Alberta Coen—Porisini~ Luigi Lavazza, and Roberto Zicari An Overview of Integrity Management in Object—Oriented Databases 38 Won Kim, Yoon—Joon Lee, and Jungyun Seo Supporting Views in Object—Oriented Databases 43 Marc H. Scholl and H.—J. Schek Algebraic Query Processing in EXTRA/EXCESS 48 Scott L. Vandenberg and David J. DeWitt ENCORE: An Object—Oriented Approach to Database Modeling and’Querying 53 Stanley B. Zdonik and Gail Mitchell Query Optimization in Revelation, an Overview 58 Scott Daniels, Goetz Graefe, Thomas Keller, David Maier, Dun Schmidt, and Bennet Vance Calls for Papers 63 SPECIAL ISSUE ON FOUNDATIONS OF OBJECT—ORIENTED DATABASE SYSTEMS + 1951-1991 THE EISTTTUIE ~ ELECTEJCAL — IEEE ~ ~.