paper on Java binary compatibility

The following paper is available from

     What _is_ Java Binary Compatibility? - Version 2 -

     Sophia Drossopoulou, David Wragg, Susan Eisenbach 

Separate compilation enables decomposition of programs into units
that may be compiled separately and linked into an executable.
Traditionally, separate compilation was equivalent to the compilation
of all units together, and modification and re-compilation of
one unit required re-compilation of all importing units. 

Java suggests a more flexible framework, in which the linker checks
the integrity of the binaries to be combined. Certain source code
modifications, such as addition of methods to classes, are defined
as binary compatible. The language description guarantees that
binaries of types (i.e. classes or interfaces) which were modified in
binary compatible ways may be re-compiled and linked with the binaries
of types that imported and were compiled using the earlier versions of
the modified types. 

However, this is not always the case: some of the changes considered
by Java as binary compatible do not guarantee successful linking and
execution. In this paper we study the concepts around binary
compatibility. We suggest a formalization of the requirement of safe
linking and execution without re-compilation, we investigate
alternatives, we demonstrate several of its properties, and we propose
 a more restricted definition of binary compatible changes. Finally,
 we prove for a substantial subset of Java, that this restricted
definition guarantees safe linking and execution. 
Dr. Sophia Drossopoulou                         tel: +44 171 594 8368
Department of Computing                         fax: +44 171 581 8024
Imperial College of Science, Technology and Medicine
LONDON SW7 2BZ, England                         email: sd@doc.ic.ac.uk