Code Importing Techniques for Fast , Safe Client / Server Access by Joseph A . Bank

In client/server systems, server integrity can be maintained by disallowing direct client access to server data and requiring communication through well-defined interfaces. Typically, this communication requires expensive cross-domain calls, or even more expensive network communication. The main goal of this thesis is to create a system with fast, safe client/server access by allowing the server to import client code. Importing code allows the client to access the server through direct procedure calls, which are much faster than the indirect access that is typically used to maintain integrity. Server integrity is maintained by using a type-safe client language and by verifying imported code. To explore the benefit of allowing the server to import code for client/server communications, a Java interface to the Thor object-oriented database has been implemented, using code importing techniques for safe database access. Performance benchmarks indicate the use of code importing in the Java interface to Thor performs 50 times faster than the Java interface to Thor using standard communication techniques. These benchmarks also indicate that the Java interface to Thor outperforms by a factor of 3 a highly optimized C++ interface to Thor. However, since Java is interpreted, and thus an order of magnitude slower than most compiled languages, imported Java code is outperformed by code written in the language of the database itself. In the future, the use of just-in-time compilation should improve the performance of Java, making code-importing even more competitive. Thesis Supervisor: Barbara Liskov Title: NEC Professor of Software Science and Engineering