TITLE: Toward Less Formal Software AUTHOR: Eugene Wallingford DATE: March 01, 2008 3:39 PM DESC: ----- BODY: This week I ran across Jonathan Edwards's review of Gregor Kiczales's OOPSLA 2007 keynote address, "Context, Perspective and Programs" (which is available from the conference podcast page). Having recently commented on Peter Turchi's keynote, I figured this was a good time to go back and listen to all of Gregor's again. I first listened to part of it back when I posted it to the page, but I have to admit that I didn't understand it all that well then. So a second listen was warranted. This time I had access to his slides, which made a huge difference. In his talk, Kiczales tries to bring together ideas from philosophy, language, and our collective experience writing software to tackle a problem that he has been working around his whole career: programs are abstractions, and any abstraction represents a particular point of view. Over time, the point of view changes, which means that the program is out of sync. Software folks have been thinking about ways to make programs capable of responding naturally as their contexts evolve. Biological systems have offered some inspiration in the last decade or so. Kiczales suggests that computer science's focus on formality gets in the way of us finding a good answer to our problem. Some folks took this suggestion as meaning that we would surrender all formalism and take up models of social negotiation as our foundation. Roly Perera wrote a detailed and pointed review of this sort. While I think Perera does a nice job of placing Kiczales's issues in their philosophical context, I do not think Kiczales was saying that we should go from being formal to being informal. He was suggesting that we shouldn't have to go from being completely formal to being completely informal; there should be a middle ground. Our way of thinking about formality is binary -- is that any surprise? -- but perhaps we can define a continuum between the two. If so, we could write our program at an equilibrium point for the particular context it is in and then, as the context shifts, allow the program to move along the continuum in response. Now that I understand a little better what Kiczales is saying, his message resonates well with me. It sounds a lot like the way a pattern balances the forces that affect a system. As the forces change, a new structure may need to emerge to keep the code in balance. We programmers refactor our code in response to such changes. What would it be like for the system to recognize changes in context and evolve? That's how natural systems work. As usual, Kiczales is thinking thoughts worth thinking. -----