MSPLS

On Saturday I went down to lovely Champaign-Urbana and gave my Earthlings and Martians talk at the annual meeting of the Midwest Society for Programming Languages and Systems (MSPLS). It was the second time I've given this particular talk to a reasonably-sized audience (or third, if you count the impromptu delivery I gave to the PL Lunch crowd on Friday) and I think it went about as well as before.

Well, as well as before but with one pretty important twist: the folks down at UIUC have been interested in using term rewriting to give semantics to programming languages, and they've been actively studying the potential there for a few years. They've grown a particular term-rewriting style out of the standard formal systems in use by the term-rewriting community that they argue is particularly good for giving semantics to programming languages; as we were watching each others' talks it struck both me and them that what they've got is very similar to Felleisen-Hieb-style context-sensitive reduction semantics. Since I go down to Champaign-Urbana all the time anyway, they suggested that I stop by the computer science department one day so we could get together and teach each other what we're doing.

So we're doing that next Monday. I'll give them a tutorial on context-sensitive reduction semantics and PLT Redex, and maybe they'll be able to teach me their particular brand of rewriting semantics and all the neat tools they've been developing there. Neat!

A personal tragedy of epically minor proportions

As I was making coffee this morning, I dropped my trusty Ozaukee Bank mug and broke it. It's the mug that I've had with me all through graduate school. It's been with me for every paper I've written here and it's probably directly responsible for every one of the ideas behind those papers. Ozaukee Bank mug, you will be missed.

As a side note, I'd like to thank whoever it is who had the original idea for coffee. You have put forward the cause of science by hundreds of years.

ICFP 2006

Paper: submitted. This is the multi-language semantics paper I've been working on forever; the one that was going to be an ICFP '05 paper, then a POPL '06 paper, and then an ESOP paper, but we never ended up submitting to any of those places because it wasn't ever finished. Now it's finally finished, so there's nothing left to do but hope.

It's called "The Meaning of Multi-Language Programs" and it's by me and Robby Findler. Here's the abstract:

Interoperability is big business, a fact to which .NET, the JVM, and COM can attest. Language designers are well aware of this, and they are designing programming languages that reflect it --- SML#, Mondrian, and Scala all treat interoperability as a central design feature, just to name a few. Still, current multi-language research tends not to focus on these languages' semantics, but only on how to implement them efficiently. In this paper, we attempt to rectify that by giving a technique for modeling a multi-language system as a composition of the models of its constituent languages. Our technique abstracts away the low-level details of interoperability like garbage collection and representation coherence, and lets us focus on semantic properties like type-safety and termination behavior.

We demonstrate the technique with a series of strategies for embedding a Scheme-like language into an ML-like language. We will start by connecting very simple languages with a very simple strategy, and work our way up to languages with sophisticated features like effects and that interact in sophisticated ways. Along the way, we prove type-soundness for each system we present. Our technique allows these proofs to be straightforward generalizations of standard type-soundness proofs for single languages.

Beyond giving simple expressive models, our studies have uncovered several interesting facts about interoperability. For example, higher-order function contracts naturally emerge as the glue to ensure that interoperating languages respect each other's type systems. Our models also predict that the embedding strategy where foreign values are opaque is as expressive as the embedding strategy where foreign values are translated to corresponding values in the other language, and we were able to experimentally verify this behavior using PLT Scheme's foreign function interface.

Once I'm ready to put the full paper online I'll post a link.

ICFP Contest 2006

As you may recall, last year I was involved in organizing the 2005 ICFP Programming Contest. Well, mark your calendars, because I just discovered by random googling that our successors at Carnegie Mellon have put up a web page for the 2006 contest, and they've even announced the dates on which it will be held: July 21 through 24.

I'm really interested in seeing what the CMU folks will come up with. I don't have any insider knowledge, just a slightly higher-than-average interest in the subject, but I'd guess they're planning something quite a bit different from the contests of recent years. Recently the contests have been essentially about writing game-playing agents; I'd bet they're going to go back to something a little more abstract.