Webinar: Notions and Notations: Babbage's Language of Thought - South Wales Branch

Charles Babbage has been called the 'great-uncle' of modern computing, a claim that rests simultaneously on his demonstrable understanding of most of the architectural principles underlying the modern computer, and the almost universal ignorance of Babbage's work before 1970. There has since been an explosion of interest both in Babbage's devices and the impact they might have had in some parallel history, and in Babbage himself as a man of great originality who had essentially no influence at all on subsequent technological development.

In all this, one fundamental question has been largely ignored: how is it that one individual working alone could have synthesised a workable computer design over a short period, designing an object whose complexity of behaviour so far exceeded that of contemporary machines that it would not be matched for over one hundred years.

The key, as is well understood in modern engineering contexts, is to abstract away from the full complexity of a concrete system. Babbage faced an overwhelming complexity barrier, and his response was to design a system of hardware abstractions, which he called his Notation. The ideas allowed him to reason in the abstract about chains of cause and effect in his mechanisms, and he believed the Notation to be his crowning achievement.

I will draw parallels between early electronic Hardware Description Languages and Babbage's notation; display some strengths and weaknesses of Babbage's approach; and speculate on underlying cause of the 150 year gap between Babbage's notation and the emergence of HDL based engineering design as a standard technique.

We shall also show video of a working steam driven implementation of Babbage's Difference Engine 2 and explain its utility and architecture.

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Speaker:
Adrian Johnstone, Computer Science Dept, Royal Holloway University of London

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Speaker biography:
Adrian Johnstone is Professor of Computing at Royal Holloway, University of London. His early research work was in machine vision and the design of real-time custom integrated vision system using the Inmos Fat-Freddy design system, which was commercialised by Racal Redac. This led to work on radical computing architectures, and from there to compiler theory and implementation, especially automatic generation of interpreters from formal specifications. He was Principle Investigator on the Leverhulme Trust funded project Notions and Notations: Babbage's Language of Thought which applied modern understandings of system engineering and design notations to Babbage's residual archive of papers, and Principal Investigator on Royal Holloway's part of the EPSRC formal semantics project Programming Languages Components and Specifications.

Elizabeth Scott is Professor of Computer Science at Royal Holloway, University of London. Her DPhil research was in Group Theory with Graham Higman at Oxford University. She continued this work at the Australian National University in Canberra before returning to the UK to work with Ursula Martin on termination proofs and formal semantics. She is the author of several well-known algorithms for generalised context free parsing, and is presently studying Babbage's idea concerning mechanisation of analysis in the context of contemporary notions of algebra.

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