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# Introduction: Frank Colcord

I came to Category Theory through trying to read Robin Milner's Space and Motion of Communicating Agents. I'm hoping once I know more Category Theory I can get further through his book. I found Milner during my search for a new approach to understanding complex systems. My earlier hero was Jay Forrester with his System Dynamics methodology. I noticed that John Sterman talked about agent modelling at the end of his book Business Dynamics. Agent modelling took me to Milner as I tried to find someone who wrote about the fundamental issues of understanding and modelling agents. Having read a bit about Azimuth project, I can see other areas of overlap. I'd really like to understand how SD models map into Category Theory language. I'd also like to study how agent modelling through Milner's work (and his successors) can provide more effective models of the same domains.

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Space and Motion of Communicating Agents Draft is this text the one you mean? There's also a book available though a bit pricey for something I'm not sure I could read/understand yet. If you have the book I'd be curious if you could comment on how much is different (via a quick scan, page count, TOC comparison) between the two.

I made an attempt to read Milner's Communicating and Mobile Systems: The Pi Calculus, but didn't make much headway at the time. It's migrated to my stack of books to read after this working through the material in this course. I may add the text you've mentioned to the list to follow it.

Comment Source:[*Space and Motion of Communicating Agents* Draft](http://www.cl.cam.ac.uk/archive/rm135/Bigraphs-draft.pdf) is this text the one you mean? There's also a book available though a bit pricey for something I'm not sure I could read/understand yet. If you have the book I'd be curious if you could comment on how much is different (via a quick scan, page count, TOC comparison) between the two. I made an attempt to read Milner's *Communicating and Mobile Systems: The Pi Calculus*, but didn't make much headway at the time. It's migrated to my stack of books to read after this working through the material in this course. I may add the text you've mentioned to the list to follow it.
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Hi Jared, yes, that's the text. I've bought the book, but find the pdf convenient. I haven't found any differences. The pagination and layout differs, so that will be frustrating for accurate citation in the future. The page count is different. The TOC has the same items.

I think Milner started a page of erratum. Milner claims that this final book clarifies and simplifies a lot of his earlier work. I think he says that Category Theory helped him to do that.

I'd love to be part of a discussion of Milner 2009 in the same format as this discussion of Fong and Spivak. Let's see how it goes. As a mature student, not part of the universities, I spent a long time looking for a place or people with whom to discuss this book in London. I've now found one person. This page lists the resources he recommends to study his text. I haven't found any better ones so far, though he had many students. I'm hoping that a good grounding in Category Theory will make my next attempt on his book more successful.

Comment Source:Hi Jared, yes, that's the text. I've bought the book, but find the pdf convenient. I haven't found any differences. The pagination and layout differs, so that will be frustrating for accurate citation in the future. The page count is different. The TOC has the same items. I think Milner started a page of erratum. Milner claims that this final book clarifies and simplifies a lot of his earlier work. I think he says that Category Theory helped him to do that. I'd love to be part of a discussion of Milner 2009 in the same format as this discussion of Fong and Spivak. Let's see how it goes. As a mature student, not part of the universities, I spent a long time looking for a place or people with whom to discuss this book in London. I've now found one person. [This page](http://www.cl.cam.ac.uk/archive/rm135/uam-theme.html) lists the resources he recommends to study his text. I haven't found any better ones so far, though he had many students. I'm hoping that a good grounding in Category Theory will make my next attempt on his book more successful. 
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That's good to read. I've downloaded the PDF (along with the text for this course) to my Kindle and I'll start reading through it in a few weeks, hopefully.

As a mature student, not part of the universities, I spent a long time looking for a place or people with whom to discuss this book in London.

I can sympathize. In college I could easily find someone to discuss ideas like these with. But afterwards, we all scattered. And many of my friends lost interest in these more formal areas, or developed more specialized interests elsewhere. And my colleagues are generally less interested in these ideas than I am.

A bit about my motivation for learning $$\pi$$-calculus:

I work in the embedded space and have my whole career. Initially it was distributed but otherwise static systems. Sensors and controllers across an aircraft. CSP turns out to be really good in this situation. It was also useful when I moved on to other projects, specifically radios. But more for modeling static configurations or the internal workings of the radios.

However, our radios construct ad hoc networks. Think dynamic, mobile cellular networks. Which is where $$\pi$$-calculus seems like a good formalism. I have had moderate success with applying other formal methods (CSP, TLA+) to our systems, but for some of the things I'd like to analyze a different approach seems necessary. And our networks can become very complicated. Which radio is the "lead"? What happens when you go beyond-line-of-site and return? We can have multiple networks near each other (partially overlapping areas) with some radios acting as bridges across the two.

Comment Source:That's good to read. I've downloaded the PDF (along with the text for this course) to my Kindle and I'll start reading through it in a few weeks, hopefully. > As a mature student, not part of the universities, I spent a long time looking for a place or people with whom to discuss this book in London. I can sympathize. In college I could easily find someone to discuss ideas like these with. But afterwards, we all scattered. And many of my friends lost interest in these more formal areas, or developed more specialized interests elsewhere. And my colleagues are generally less interested in these ideas than I am. A bit about my motivation for learning \$$\pi\$$-calculus: I work in the embedded space and have my whole career. Initially it was distributed but otherwise static systems. Sensors and controllers across an aircraft. CSP turns out to be really good in this situation. It was also useful when I moved on to other projects, specifically radios. But more for modeling static configurations or the internal workings of the radios. However, our radios construct ad hoc networks. Think dynamic, mobile cellular networks. Which is where \$$\pi\$$-calculus seems like a good formalism. I have had moderate success with applying other formal methods (CSP, TLA+) to our systems, but for some of the things I'd like to analyze a different approach seems necessary. And our networks can become very complicated. Which radio is the "lead"? What happens when you go beyond-line-of-site and return? We can have multiple networks near each other (partially overlapping areas) with some radios acting as bridges across the two.