The fourth international conference on Extending Data BaseTechnology was held in Cambridge, UK, in March 1994. Thebiannual EDBT has established itself as the premier Europeandatabase conference. It provides an international forum forthe presentation of new extensions to database technologythrough research, development, and application. This volumecontains the scientific papers of the conference. Followinginvited papers by C.M. Stone and A. Herbert, it contains 31papers grouped into sections on object views, intelligentuser interface, distributed information servers, transactionmanagement, information systems design and evolutionsemantics of extended data models,accessing new media, joinalgorithms, query optimization, and multimedia databases.

The object management group standardization of object technology.- Databases in distributed systems: The new frontier.- Type derivation using the projection operation.- Subsumption between queries to object-oriented databases.- Composite-object views in relational DBMS: An implementation perspective.- Matrix relation for statistical database management.- Deductive database support for data visualization.- Subsumption-free bottom-up evaluation of logic programs with partially instantiated data structures.- Schema equivalence in heterogeneous systems: Bridging theory and practice.- Virtual schemas and bases.- Role-based query processing in multidatabase systems.- Content routing for distributed information servers.- A unified approach to concurrency control and transaction recovery.- Algorithms for flexible space management in transaction systems supporting fine-granularity locking.- Indexing alternatives for multiversion locking.- A rule-based approach for the design and implementation of information systems.- On behavioral schema evolution in object-oriented databases.- Representing and using performance requirements during the development of information systems.- A model-theoretic semantics of the multilevel relational model.- On the semantics of (Bi)temporal variable databases.- Correctness of ISA hierarchies in Object-Oriented database schemas.- Power efficient filtering of data on air.- Video information contents and architecture.- Optimizing storage of objects on mass storage systems with robotic devices.- On the estimation of join result sizes.- DBJ - A dynamic balancing hash join algorithm in multiprocessor database systems.- Tabu search optimization of large join queries.- The implementation and performance evaluation of the ADMS query optimizer: Integratingquery result caching and matching.- Optimization of nested queries in a complex object model.- A multi-threaded architecture for prefetching in object bases.- Supporting full-text information retrieval with a persistent object store.- Bit-sliced signature files for very large text databases on a parallel machine architecture.- Schemas for telling stories in medical records.