TITLE: Simplifying the Evolution  of Java Programs

HALF DAY
MORNING on
Monday, May 19, 1997


TUTORIAL PRESENTERS:
Linda Seiter
Computer Science Department, Boston College,
Chestnut Hill, MA 02167; email: seiter@cs.bc.edu.

Karl Lieberherr, Doug Orleans
College of Computer Science, Northeastern University,
Cullinane Hall, Boston, MA 02115; email:  {lieber|dougo}@ccs.neu.edu.

TUTORIAL CONTENT:  
We present an in-depth look at the ability of existing
models and languages to support different forms of reuse and evolution. The
intended tutorial participants are experienced object-oriented programmers and
analysts who want to improve the adaptability of their models and programs.

We present a key concept in supporting behavioral evolution:
the context relation.  The relation is meaningful at both the
design and implementation level.  At the design level we present a simple
extension to the Unified Modeling Language for including the context
relation and the new type of class it introduces: context
classes.  At the implementation level we demonstrate how to develop Java
programs using context objects.  We demonstrate how context objects
can be used to easily model and program patterns such as the Adapter, Bridge,
Chain of Responsibility, Decorator, Iterator, Observer, State, Strategy, and
Visitor.

We present techniques for achieving dynamic behavior in a
static, class-based model and language.  We focus on two forms of behavior
evolution:

1. dynamically altering a method implementation for a single object, and
2. dynamically altering a method implementation of a class (affecting all 
   class instances) during the execution of some task.

We present the public-domain programming tool Demeter/Java which implements
a special kind of context object, called a visitor object.
To enable the direct expression of visitor objects and to express
traversal strategies for objects
in Java, we present a simple extension to Java (the Demeter/Java language)
and show how it is translated back into Java.
The benefits of Demeter/Java are that programs become
more flexible, both structurally and behaviorally, and simultaneously
they become shorter.


TUTORIAL OUTLINE AND OBJECTIVES:
The  outline for this half-day tutorial is as follows:

1. Introduction to design patterns and software evolution.
2. Discussion of existing object-oriented models and languages, and their
approaches to supporting evolution.
3. Example patterns such as  strategy, state, iterator, visitor using existing
models and languages.
4. Introduction to behavioral evolution using context objects, and
implementation techniques for Java.
5. Demeter/Java: The structure-shy traversal and structure-shy object patterns.


After completing the tutorial, you will be able to:
1. Develop more flexible and simpler object-oriented designs.
2. Describe your software in terms of executable patterns.
3. Apply Demeter/Java to develop your applications with lower maintenance costs.
4. Achieve dynamic behavior in static, class-based languages.


TUTORIAL PRESENTERS: 
Karl Lieberherr is a Professor in the College of Computer Science at
Northeastern University. His current research interests are methods and tools
for developing adaptable software for open systems, with special emphasis on
adaptive software.
Karl Lieberherr is the author of the book: "Adaptive Object-Oriented Software:
The Demeter Method with Propagation Patterns" published by PWS Publishing
Company, 1996, ISBN 0-534-94602-X. The book presents patterns and techniques
for managing structural evolution. Karl Lieberherr is Editor-in-Chief (with
Roberto Zicari) of TAPOS (Theory and Practice of Object Systems), A John Wiley
journal.  For more information on course, author and book, see WWW URL
http://www.ccs.neu.edu/home/lieber.

Linda Seiter is a visiting professor at Boston College. Her current research
interests include semantics of languages that support evolution and reuse. For
more information, including links to her PhD thesis based on design patterns
for managing evolution, see URL http://www.cs.bc.edu/~seiter.

Doug Orleans is a PhD student at Northeastern University, and the
principal architect of Demeter/Java.