Browsing in Explicit Metaclass Languages :
An Essay in Reflective Programming Environments

Francois Rousseau, Jacques Malenfant
Universite de Montreal
C.P. 6128, Succursale A
Montreal, Canada, H3C 3J7
e-mail: {rousseaf, malenfan}@iro.umontral.ca

Abstract

The development of adapted programming environments is mandatory in order 
to deliver reflective languages to real world users. It is generally 
assumed that reflection aids in the development of programming environments. 
However, its use may also give rise to certain difficulties. For example, 
it prevents programming tools from making strong assumptions about 
language structure and semantic. Our paper tackles this rather large 
problem by concentrating on the case  of the browser in the context 
of explicit metaclasses. We first propose a new browser architecture 
that is better adapted to explicit metaclass languages. The new 
browser uses a decentralized approach to manage information related 
to the internal structure of classes. The decentralized approach 
involves the use of third-party objects named Descriptors, which 
provide individual class representations. Next we implement this 
architecture in Classtalk under VisualWorks. The VisualWorks interface 
generator is used to assist metaclass designers with the task of 
incorporating descriptors for new class structures into the browser. 
This latter is effective on several ClassTalk metaclasses as, for 
example, on a CombinationClass, which has three method dictionaries.