Author: geoff

Interrelated aspects of interaction

For the last few weeks I’ve been trying to figure out how to write up an idea that’s been bugging me. I think it’s an interesting idea, but until I can actually write it up I won’t be sure. So today I just decided to blurt it out into the blog, relatively unformed, certainly unfinished, definitely half-baked.
There seems to be an expectation today that distributed computing means web services – or that it will do, just as soon as the various standard bodies and corsortia get their acts together. I’m unconvinced. I see three ways – three axes, if you like – in which there are strong arguments for widely differing and incompatible positions; when you combine these, you get a 3D design space which is much bigger than what web services aficionados would claim. (And just to be even-handed, it’s also way beyond what we can do naturally with things like Jini and RMI.)
I’m just going to describe these three axes, without attempting much justification. Zealots can argue all they want….

  • The first axis is interface typing. At one extreme, a service can only accept a message of a single type, encoded in one way; if the request doesn’t match exactly, no interaction is possible. (Think CORBA or RMI.) At the other extreme, a service will accept any type of message, although of course it may have to reply “Sorry, I don’t understand”.
  • The second axis is control. At one extreme, the behaviour of the client and the service is rigidly specified, and the binding between the two is explicitly controlled and predictable. (Choreography languages, workflows, message exchange patterns, protocol FSMs come to mind.) At the other extreme, components are substantially autonomous; a client can search for a service at run time, a service can choose to delegate a request to a third party, and parties can renegotiate their interaction patterns on the fly.
  • The third axis is synchronicity. At one extreme is the traditional synchronous request-response style, which is directly derived from the procedure call paradigm. The service is essentially passive; indeed we usually draw this interaction with a single thread of control running from client to server. There are other synchronous interaction patterns, typically described by state machines. At the other end of the spectrum, messages may be sent between the parties without temporal constraints. Partners may repeat messages, “interrupt” each other, or even “change the subject”. (I don’t want to get into the definition of [a]synchronous right now – that’s a whole blog piece on its own. Let me just say that it’s about the pattern, not the implementation technique; I’m not interested in dependency on a transport connection or blocking i/o.)

To summarise, we have:
Interface typing, from strongly typed to untyped
Control, from choreographed to autonomous
Synchronicity, from synchronous to asynchronous
Now strongly typed, choreographed, synchronous is very familiar: it’s the classic RPC style. Untyped, choreographed, synchronous is what we find in the WWW today. At the other extreme, untyped, autonomous, asynchronous corresponds to the Holy Grail of the agents and semantic web community; it’s also a pretty good description of human beings, which should come as no surprise.
What I find interesting is that I can think of really compelling use cases for both ends (and some middles) of each of these axes. One size will certainly not fit all. And in some cases we want to have our cake and eat it too:

  • On control: I want the elements in my distributed system to be substantially autonomous and self-organizing, to improve scalability and avoid single points of failure. On the other hand, I want to be able to define policies that will influence the self-organization, and to have ways of observing and measuring what’s going on.
  • On typing: I want the safety and efficiencies that arise from working with predefined types with efficient encodings. On the other hand, I’d like to be able to refactor my distributed system by introducing generic facades for brokering without having to teach my broker about every service type that it might have to support.

Anyway, that’s what I’ve been thinking about. Now to see if it makes any sense in the cold clear light of blog….

"Free Lunch Republicans"

Terry just posted a pointer to a piece by akiru:
Waking up to NPR, as you do, I heard an analyst use a golden phrase to describe half of the Congressional inactivity on fixing Social Security. Free Lunch Republicans. Gosh that’s beautiful. It’s got such wide applicability. Everytime they trot out the old chestnut about “Tax & Spend” Democrats, you can reply that only Free Lunch Republicans would imagine that you can keep spending money without having some first. It’s particularly exquisite because there is that brand of “Libertarian” Republican who is only too fond of reciting TANSTAAFL at the drop of a rhetorical hat.
Please feel free to disseminate widely.
And so I am. And so should you.

"The car has become an article of dress without which we feel uncertain, unclad and incomplete in the urban compound."

Well, Marshall McLuhan’s quotation may be accurate, but sometimes the car feels like Heracles’ tunic steeped in the blood of Nessus. All of which is an absurdly pretentious way of saying that I took my car in to the dealers this morning, “unwontedly” as it were. I carefully described the shudders from the transmission that I had felt on my way home last night, and pointed out the blinking (and undocumented) icon that had appeared on one of the dashboard displays. And after a protracted examination, it was announced (“Do you want to sit down first?”) that the vehicle needed a replacement transmission, which would cost $3,000. (“Of course, you could opt for a transmission rebuild for about $2,500, but…”, said the service manager, shaking his head slowly to imply that only a palooka would do something so foolish.)
I rather wish that this was an uneconomic thing to do; that I could simply say “Hell, no!” and get myself a new car. Sadly, the car in question (99 Mercury Cougar 2.5V6) only has 65K miles on it, and the price to repair it is less than its trade-in value (Kelly gives $5,000, NADA gives $6,175), so I guess I’ll bite the bullet.
But I feel Heracles’ pain….
[UPDATE: Several friends have urged me to look into getting the car fixed at a specialist transmission shop like AAMCO. I’ll think about it, but the logistics are extremely complicated because of travel commitments.]

Update on The Project

As I mentioned, I’m in the middle of a project to read the first six of Stephen King’s Dark Tower books in time to be ready when the seventh and final volume is published in mid-September. I’m pleased to report that it’s going well: I finished the fifth volume, Wolves of the Calla, late last night (which provoked some weird and wonderful dreams!), and this evening I picked up a copy of Song of Susannah. At this rate I’ll be done well before September 21st, even allowing for a week in England between now and then. The trip to England – specifically to Oxford – will, of course, include at least one visit to Blackwell’s bookshop in Broad Street, pictured here. I definitely won’t run short of reading material….

Art Deco at the MFA

La Bella Raphaela by Tamara de LempickaWe just got back from the Boston MFA (Musem of Fine Arts) where a new Art Deco exhibit has just opened. It’s organized into three sections, roughly 30-50-20 percent respectively. The first presents various ideas and styles that influenced art deco – everything from Classical Greek and Egyptian, through African and Meso-american patterns and colours, to Russian ballet costumes.
The second section is art deco proper: the tsunami of styles – individual yet linked – that were launched on the world at the 1925 Paris Exhibition. I felt that the organizers of this show cast their net a little wider than I would have done. Man Ray’s Electricity, while brilliant, doesn’t feel as though it has anything to do with art deco. Nor do the wonderful miniatures (postcards, really) of Josephine Baker; not everything in Paris in the 1920s qualified as art deco. But enough quibbling: overall, this section was superb. My favourite piece was Tamara de Lempicka’s stunning nude La Bella Raphaela (shown above; click for full size). The scanned image doesn’t do justice to the work, particularly the breathtakingly sumptuous reds of her lips and the cloth she’s lying on.
The final section showed the impact of art deco on design in the USA. (Recall that the USA was offered a place at the original 1925 exhibition, but, as the MFA’s program notes, The USA declined to participate on the grounds that �there was no modern design in America�.) There are some gems here, illustrating especially the distinctive “streamline” twist that America introduced. And the huge boxwood model of the Rockefeller Center shows how art deco ideas were incorporated into the design of New York’s skyscrapers.
Overall, a very cool show. I bought the t-shirt.

I may be distracted for a few days weeks….

Doom 3 boxI just picked up a copy of Doom 3. My investment in an ATI Radeon 9600 when I bought this PC is about to pay off. (Of course I could always step up to an x800 XT Platinum and crank up my pixel fillrate from 1.3Gpixels/sec to 8.3Gpixels/sec. A snip at $499… which is almost as much as I paid for the rest of the PC! Yeah, yeah, yeah….)
Actually, the choice of a 9600 was deliberate. I didn’t want to have to upgrade my power supply to 300 Watts, which a 9800 would have required. I wasn’t just being a cheapskate: I’m a software guy, and I don’t do hardware upgrades.

Fahrenheit 9/11

We finally saw F9/11 this morning. Brilliant agit-prop. I don’t care about categories: if critics complain that it isn’t a documentary because it doesn’t follow journalistic standards of being “fair and balanced” (oops….), then find another category for it. Emotional? Damn right! How do you talk to a woman who’s lost a son in Iraq without dealing in emotions? And if you can look at the broken bodies of Iraqi children and American soldiers without emotion, I pity you.
A lot of people have latched on to the wrong issues from this film. And many people are criticizing it without even seeing it. (See, for example, Rep. David Dreier on Real Time With Bill Maher.) Please, make up your own mind. If you haven’t seen it, I really think that you should. If you are from the USA, or the UK, or Australia, you need to see what is being done by your government in your name. It isn’t pretty. You’ll see blood, bodies, coffins, amputated limbs: that’s what war is all about. I hope you won’t use Barbara Bush’s beautiful mind excuse. In the words of Lou Reed, “This is no time for my country Right or Wrong/remember what that brought/…/This is no time to turn your back.

CD of the Week: Bob Dylan's "Live 1966"

CD cover for Bob Dylan Live 19661966. How old was I – 15, 16? Just starting 6th Form at the Royal Grammar School, High Wycombe. (I was in 6T1, taking maths, physics, and economics – a combination that drove my teachers crazy.) I was listening to more classical music than pop, folk, or rock. I was most aware of the Beatles, the Stones, the Kinks, Eric Burdon and the Animals, and Manfred Mann. However there were a number of American artists getting my attention – the Byrds, who had hit with Mr. Tambourine Man the year before, and then the Beach Boys, the Mamas and Papas, and the Supremes. (The last three mostly because my best friend John Hughes never stopped playing them, and I spent a lot of time at his house hanging out with his sister, Gwyneth… but I digress.)
And then there was Bob Dylan. From my perspective, he made an almost magical transformation: one minute he was a conventional socially-conscious folk singer, hanging out with Joan Baez and the Greenwich Village folk crowd; the next, he’d become a surrealistic poet. I didn’t have any connection to the beat scene; I didn’t listen to jazz, but enigmatic poetry was cool. Burroughs. Ferlinghetti. Ginsberg. Brautigan. Even Gerard Manley Hopkins (ignoring the religious metaphors – how pretentious). With no Google to help, I carefully transcribed the lyrics to Desolation Row and Ballad of a Thin Man, and marvelled at them. Was there some deep meaning there, or were the immediate impressions the beginning and end of it? At 15, such questions can seem profound… and perhaps they still are. No matter.
For Dylan’s early fans, his “plugging in” was a really big deal. Not so to me: Dylan, along with Simon and Garfunkel, Laura Nyro, and Leonard Cohen, was primarily a poet, and in my teenage head “poetry” and “pop music” were quite distinct categories. It took a couple of years for that to break down. The Beatles didn’t do it – they were sui generis – but albums like the Jefferson Airplane’s “Surrealistic Pillow” started the rot, and with “Electric Ladyland” Jimmy Hendrix blew the doors down. And of course one of the songs on that album that did the damage was All Along The Watchtower – that guy Dylan again.
Bootleg albums? Of course: every self-respecting student in the late 60s and early 70s had a couple of bootlegs in their record collection. And I remember that I had the chance to buy the most frequently bootlegged Dylan recording: the legendary “Royal Albert Hall” set. But at the time my interests were elsewhere: I chased Cream, and Led Zeppelin’s “Blueberry Hill” instead.
Fast forward 35 years: I find myself reading a review of the official CD release of Dylan’s “Royal Albert Hall ’66” set. It turns out that it was actually recorded at the Free Trade Hall in Manchester (a venue with fond memories, but that’s another story – maybe). And according to all the critics, it’s one of the best live rock’n’roll recordings of all time. So last week I bought it. And the critics were right. It’s the best. (I guess I forgot the pantheon: Dylan, Lennon, Hendrix, Miles. Only one left….)
I sit here, trying to remember what it was like to listen to Dylan when I was 15, and then hearing the sheer presence in this live recording. The imagery of Desolation Row is still as powerful, and enigmatic, and breathtaking as ever. And when my guard is down, Leopard-Skin Pillbox Hat sneaks up on me, and I find myself savouring the glorious absurdity of:
You know it balances on your head
Just like a mattress balances
On a bottle of wine
Your brand new leopard-skin pill-box hat
What a time.