Monthly Archives: June 2004

Dave Orchard on protocol evolvability

A good post by David on the relationship between data format and protocol extensibility and evolvability. I’m not sure I totally agree with his conclusion – that “protocol designers […] shouldn’t have high hopes that they can regularly provide for compatible protocol evolution” – but the bulk of it makes sense. I also think he’s approaching it from too theoretical a POV, since there are practical considerations that change the dynamics he’s studying (as I mentioned to him).

However, he finishes with this whopper;

As an afterward, it may be worth pursuing trying to solve problems of protocol evolution by examining whether the use of a constrained protocol, ie HTTP, provides any greater evolvability for protocols

That kinda came out of left field, no? I don’t see how that follows from what he wrote. I agree, of course, but just because a constrained interface provides self-descriptive messaging, and self-descriptive messaging provides better evolvability characteristics than the alternative, since the semantics of the message are unambiguous. This is in constrast to an SOA style message, where the most important semantic – the operation – is actually purposefully removed from the message.

I’m looking forward to his next post, which I anticipate to have a title something like “Oh my, you mean HTTP and RDF are what I’ve been looking for all along?!”. 8-)

All PCd out

[Oops, I forgot to promote this to my “live” weblog last week. Here goes.]

Had a blast at the Middleware 2004 Program Committee meeting in Toronto this weekend. I got to catch up with my old dist-obj buddy Doug Lea, as well as meet some people whose work I have at least a passing familiarity with such as Roy Campbell, Stefan Tai, and Chris Gill. Unfortunately Werner couldn’t make it en corpo – it would have been good to talk face-to-face with him about REST, SOA, distributed objects, etc.., – but he was able to dial-in which was appreciated.

I hadn’t heard about this conference before being invited to be on the PC, so wasn’t exactly sure what to expect in terms of paper and organizational quality (though after seeing who was involved, I was less concerned 8-), but after this weekend, I’m confident it will be an exceptional conference. Please consider attending!

Tim Bray on Mark Hapner on WS-*

Tim writes;

In recent decades, he points out, good new technologies have first appeared in rough-and-ready form on the Internet, then migrated into the enterprise. […] But all the WS-* hullabaloo is trying to go the other way; […]

Yep, I’ve been pointing this out for years.

But why is this so? Mark’s observation are empirically correct, but how do you explain it? I believe the study of software architecture provides a hypothesis; Intranet based architectures are insufficiently constrained to provide the necessary architectural properties to manage an abundancy of trust boundaries. An intranet is a special case of the Internet in this way, and therefore architectural styles developed for the latter are not, in general, suitable for the former. But because the Internet is the general case, architectural styles developed for it are transferrable to the intranet.

I’ve been recently thinking about this in terms of “Fitness Landscapes”, which I learned about from one of Stuart Kaufmann‘s books a few years ago. But Christoper Alexander‘s work on architecture and pattern languages is also relevant. In fact, I bet that in most fields there’s some guru who’s made this same fundamental observation.

Memories of Honolulu; Makana

I contributed some of my WWW2002 photos to the very cool W3 Photo project last week, and stumbled upon some others there that reminded me of what an awesome time I had in Honolulu. There was this one party in particular, at the “home” (read; “estate”) of Kevin Hughes, that I’m sure I’ll never forget. Located on top (and I do mean top) of one of the rolling mountains behind Honolulu city, it had the most spectacular view; you could see all the way from Diamond Head on your left, to Pearl Harbour on your right, with Honolulu seemingly below you; breath-taking.

Later in the evening, Kevin introduced a friend of his, Makana, who proceeded to enchant us on his guitar amoungst a mini-studio Kevin had setup in his living room. Makana told us that he played in “slack key” style which I hadn’t heard about before, but fully enjoyed … I think; I’m not certain that I was able to identify that particular style in amoungst the melange of styles he exhibited, primarily (to my untrained ear) classical, blue grass, and folk. Really really wonderful. With the warm, gentle breeze blowing through the house as Kevin opened many of the windows, most of us were hypnotized.

But, as if all that wasn’t enough fun, one of Kevin’s friends who I had seen dragging in a cooler earlier, cracked it open to reveal a damned fine wine collection which included a bottle of 1990 vintage Penfold’s Grange. Despite a corking incident, I managed a fairly healthy glass which I nursed for the next hour. Wow wow.

Anyhow, I was disappointed to learn while looking up Makana’s web site, that I missed him in Toronto a couple of weeks ago. Though perhaps that’s for the best; Massey Hall just can’t top a breezy mountain top paradise on Oahu, and a cosy, private performance for 25. But FWIW, if he’s coming your way, and you enjoy guitar, I’d highly recommend seeing him.

P.S. Damn I miss travelling.

Update; Savas, you suck 8-(