Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!cwjcc!tut.cis.ohio-state.edu!pt.cs.cmu.edu!sei!ajpo!eberard
From: eberard@ajpo.sei.cmu.edu (Edward Berard)
Newsgroups: comp.object
Subject: Reflection In Object-Oriented Systems
Keywords: reflection, definitions sought
Message-ID: <599@ajpo.sei.cmu.edu>
Date: 12 Oct 89 15:00:14 GMT
Lines: 56

I have been researching the concept of "reflection" in object-oriented
systems, e.g.:

	- The series of papers in the OOPSLA '89 proceedings:

		- "Metaclass Compatibility" by Nicolas Graube

		- "Computational Reflection in Class Bases Object
		  Oriented Languages" by Jacques Ferber

		- "Reflective Facilities in Smalltalk-80" by Brian
		  Foote and Ralph Johnson

	- Pattie Maes oft cited article "Concepts and Experiments in
	  Computational Reflection" in the OOPSLA '87 proceedings

	- Nicolas Graube's article in the ECOOP '88 proceedings:
	  "Reflexive Architecture: From ObjVLisp to CLOS"

I am interested in accomplishing the following:

	1. Developing a definition for reflection which reflects the
	   _concept_, not a particular _implementation_ of reflection.

		a. I would like a fairly informal, intuitive
		   definition of the concept, preferably not tied to
		   any particular programming language

		b. I would also like a pointer to a _generally_
		   _accepted_ (if such a thing exists) formal
		   (mathematical) definition of reflection.

	2. Developing a taxonomy of reflection. Specifically, there
	   are types of reflection which are conceptually different
	   from each other, and one, or more, _conceptual_ models for
	   each of these different types of reflection. Of course,
	   taxonomy implies nomenclature, definition, and
	   classification.

	3. Developing a rationale for considering reflection. While I
	   will admit that the problem is intellectually intriguing, I
	   am looking for "practical" reasons for considering
	   reflection, e.g., why would your "typical object-oriented
	   software engineer" be interested in reflection?

I was in the process of formulating my own set of answers to the
above, when I remembered something someone said to me at OOPSLA '89:
"We just had a Birds of a Feather session on reflection, and there
still seems to be a great deal of confusion on just what reflection
is."

What are your thoughts on the matter?

				-- Ed Berard
				   Phone: (301) 353-9652
				   FAX:   (301) 353-9272