63 Putting Metaclasses to Work

Ira Forman, IBM

Convention Centre
Room 19

The purpose of this tutorial is to demystify metaclasses and demonstrate how they can be used to increase productivity and reusability in object-oriented programming. The tutorial starts from first principles to construct an object model that is class-based (every object has a class) with first-class classes (every class is an object). After the object model is established, we introduce a metaobject protocol for manipulating the model. The metaobject protocol supports a new dimension for inheritance: inheritance of metaclass constraints. Based on this, we describe facilities required for composable metaclasses, that is, how a metaclass imparts to its instances the composite properties of its ancestor metaclasses. We conclude by demonstrating a number of useful metaclass that do compose with each other.

Attendee Background: The tutorial is intended for programmers who have a good understanding of object-oriented programming. Although the tutorial defines "class," "method," "inheritance," etc., the tutorial is definitely an advanced course and one has to know the basics. Just as one has to know about shapes and angles before taking high school geometry.

Dr. Ira R. Forman works for IBM in Austin. As a member of IBM's Object Technology Products Group, which has produced the SOMobjects Toolkit, he worked on the SOM Metaclass Framework. He started working in the area of object-oriented programming in 1984, when he worked at ITT Programming Technology Center. Forman received his Ph.D. in Computer Science from the University of Maryland, where he studied under Harlan Mills. Forman's specialties are object-oriented distributed systems and object composition.

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Last edited 22 September 1998 15:09:50