ACM Queue: A Conversation with Steve Ross-Talbot

Steve Ross-Talbot has more than 20 years of experience leveraging cutting-edge research and applying it to real business problems. Recently he founded Pi4 Technologies where he and his team draw on the field of the pi-calculus to improve the ability to design, automate, and analyze business processes.

The interview goes into more detail than you might expect,

Surely, we should be able to prove something about interaction. I started looking at other papers that leveraged the work of Robin Milner and the pi-calculus and found some fundamental work by Vasco Vasconcelos and Kohei Honda. Their work looked at something called session type...

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Skeptical at first, but...

I was skeptical at first, having heard several other groups claim to be "using the π-calculus" as a basis for business process modelling. Too often, those words have seemed more PR in reality. But Ross-Talbot sounds like he's actually doing what he's claiming. It's great to see use of a formal tool like this percolate out into the "real world".


I enjoyed this interview in the print version, and was awaiting its appearance online so I could pass it around... It's got just enough detail to get me interested, and I agree with Allan: it sounds like he's actually doing what he's talking about doing, which is sadly not always true.

Response to comments thus far

Many thanks for the +ve comments.

I very much appreciate the scepticism of people who claim to be doing things using theory when in fact they are not. I have the same deep suspicion. This is why I work with Honda, Milner, Yoshida and others. There is a need for engagement between industry and academia to move some of this stuff forward. The benefits, as I am sure you are all aware is profound. Alas this is not always seen by short term objectives that one finds in industry.

We don't claim to have done it all. We doing it and it is raising more questions. I would strongly recommend and also ask anyone interested to join the crew at We have some active discussion groups. We would welcome debate as this helps enforce rigour.

No clear idea when the advance type system will be in operation. It will come sometime this year as a plugin to the eclipse project. Marco Carbone and Kohei Honda backed up by Nobuko Yoshida are very active in doing this. Robin is involved as a guardian whom we seek comments from - he is very busy.

Oddly enough none of the question where choreographed. We did it as a single take over the phone. I was so busy doing other things prior to it that I forget about it and also did not realise the importance of ACM Queue. I found out after when I googled for it. So what you read is very much how I see things without any side any rehersal at all whatsoever.

I'm somewhat surprised at how it all hang together but then I am always surprised at how this whole thing has taken off and seems to be gathering a momentum all of its own.

At the end of the day I was just lucky to know the right people and call some good shots. It all about the team (the W3C WG and in particular Honda, Carbone, Brown, Yoshida, and of course Milner) and their contributions - credit to them. I'm just the spokesperson.


Steve T

Interesting tidbit

I glanced over this story when it was first sumbitted without much interest. Words like "leverage", "pi-calculus" and "business processes" make my eyes glaze over. I went back and read the interview after reading the comments here, and I'm glad I did. In case anybody is of a like-mind, here is an excerpt that got my attention:

The long-term aim was to be able to ask questions about systems, and the sorts of questions that we wanted to know were derived from causality. For example: Is our system free from livelocks? Is our system free from deadlocks? Does it have any race conditions?

These are the sorts of things that consume about half of your development and test time. Certainly in my experience the worst debugging efforts that I've ever had to undergo had to do with timing and resource sharing, which showed up as livelocks, deadlocks, and race conditions. Generally, what Java programmers were doing at the time to get rid of them, when they were under pressure, was to change the synchronization block and make it wider, which reduced the opportunity for livelocks and deadlocks. It didn't fix the problem, really; what it did was alleviate the symptom.

I would also like to highlight that the foundation for their work is open source:

pi calculus

With all due respect, the idea of using Pi calculus in BPMS is not exactly new - Intalio's product (or at least their original BPML-based version) was built on the same [ The underpinning of their current BPEL-based version is less clear to me. ]

That said, I would like to see a comparison between the approach taken between the two.

Dislaimer: I am not affiliated with Intalio in any way, other than having met with them regarding their product in 2002.

Intalio's product

I would also like to see how Intalio's product is based on pi-calculus. My current understanding is that it "informed" the design. I have not seen any mathematical support for the phrase "informed". I know for a fact that Enigmatec's base platform, called RIF, was also "informed" by the pi-calculus. But I also know that it is devoid of mathematical proof. Rather you can find the notion of a port/channel, you can find the notion of choice and so on but that does not mean it is formally based upon rather it is informally based upon. WSDL 1.X is also informally based upon the pi-calculus.

Sorry to rant but it goes back to what Allan said "Too often, those words have seemed more PR in reality". So when we do look for comparison, and I would very much welcome it, let us make sure that the proofs are there too. We have done all our work in the public eye in the context of W3C and all of the tools are Apache open source so we are trying to be very transparent in part to get better feedback and in part to ensure we can engage with academia.


Steve T

When I'm reading blurb,

When I'm reading blurb, "informed by" just means "we looked at it and allowed it to guide or steer us in some places". This suggests you can be informed by good work and still do something really stupid. YMMV?

Better Math, Better Processes?

Stan Kelly-Bootle published a piece called The Calculus Formally Known as Pi in the May issue of ACM Queue. In it, he discusses, among other things, the aforementioned interview with Steve Ross-Talbot. A couple of interesting references:

The Calculus Formally Known as Pi

Here we go.

In the queue

Actually, this one is in my queue of things that might end up on the homepage (after I find the time to read it of course...)

In a similar vein

In a similar vein, here's Wil van der Aalst's Pi calculus versus Petri nets: Let us eat "humble pie" rather than further inflate the "Pi hype". Frank Puhlman has a discussion paper that demonstrates how to model the Petri net from van der Aalst's paper in the pi-calculus (which of course does nothing to negate van der Aalst's excellent points about the "pi-hype").

Note that van der Aalst's major complaint is basically that the pi-calculus isn't the only game in town for business process work, but is being hyped that way. Which is a fair criticism, but takes nothing away from Ross-Talbot's work. More importantly, unlike several of the efforts that van der Aalst complains about, the Pi4 crowd seems to really be using the pi-calculus, instead of just talking about it a lot.