In most of the object oriented programming systems, the run time conversion of objects has been supported by mixins which package the sets of operations within them that can be mixed into other, usually larger, classes. Although the method based on the mixin which adds functionality to classes is quite popular, it may be inefficient and unnatural to handle run time conversion of objects.
In order to overcome the shortcomings of the mixin, Hendler proposed the concept of "enhancement" which adds the functionality to instances. But, he also noted the problems associated with his concept. In this thesis, we propose an extension of "enhancement" by introducing the character hierarchy in place of the class hierarchy. The performance of the extension of "enhancement" is demonstrated. A prototype language POOPL (Prototype Object Oriented Programming Language) is implemented with Quintus Prolog on SUN 3/50 workstation.
