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The Informatics of Time and Events

Excerpts from the Inaugural Lecture - 28 March 2013
Gérard BERRY
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Source: La lettre, no. 36, May 2013

Cet article est une traduction de :
L’informatique du temps et des événements

Texte intégral

Gérard BerryAfficher l’image
Crédits : Patrick Imbert - Collège de France

1The new Chair of Informatics “Algorithms, Machines and Languages”, which I have the honour of holding is the first permanent Chair of Informatics at the Collège de France.

2It follows on from the introduction of informatics in the Liliane Bettencourt Chair of Technological Innovation and sub­sequently the creation of the Chair of Informatics and Digital Sciences, in which I had the honour of taking part. The creation of a permanent Chair is great news for my ­community, as it is the highest accolade that can be paid to the autonomous­ discipline that computer science has become.

3Informatics is comprised of five main subdomains: the interfaces through which information from the real world is digitized and acted upon, the now countless digitized data, the algorithms with which these data are conceptually manipulated, the languages that allow for these algorithms to be formally specified and written in the form of executable programs, and the machines which execute these programs. I chose this title for the Chair as I have focused primarily on the last three domains and their numerous interactions.

4In the first few years, I intend to devote my lectures and my research to the informatics of time and events, which is crucial in many domains of application: the real-time control of transport systems, industrial systems and a wide variety of cyber-physical systems; electronic systems on chips replacing the single-function circuits of the twentieth century; computer-based simulators of complex physical or industrial systems; the orchestration of web services to build new applications by composing existing services; musical composition and interpretation mixing human musicians and computers.

5Surprisingly, classical informatics makes virtually no mention of time and only manages events using programming primitives which, to say the least, are rustic and lack clear semantics. Since the eighties, French research, which is at the forefront of this domain, has been developing new programming languages called synchronous languages, which are mathematically well defined and understood, adapt well to the above-mentioned domains and are very successful industrially. But applications are developing rapidly, and extensive research still needs to be carried out to extend these languages’ initial principles to richer situations like multi-clock circuits, geographically distributed control systems, or the correct coordination of the independent simulators of parts of systems to build their global simulators.

6I will first show that while spoken language is pleasantly embellished, it is by no means adequate for talking about time precisely, with its “time that flies” on the one hand and its “long years” on the other. I will also show that the everyday identifi­cation of time with mathematics’ real line is too limited for informatics applications. These applications require that we consider time at different levels of abstraction by linking ­par­ti­cular events and durations through the notion of the thickness of the instant, which is crucial to understanding the functioning of electronic circuits and real-time programs. I will generalize the pro­cessing of physical time expressed in seconds to that of multiform times brought about by the repetition of a given event, thereby unifying expressions like “in ten seconds”, “in ten steps” or “the tenth time pressing a button”. I will show that these notions can be beneficially incorporated into programming languages that are both perfectly mathematically defined and efficiently implementable through their translation into standard software codes or electronic circuits. I will discuss the still poorly understood relationship between continuous time and discrete time, which are key for properly simulating complex systems. Finally, I will consider how to reason about time- and event-handling programs using temporal logics or other mathematical formalisms, and how formally to prove their correction – another domain where France is at the forefront of research.

• Inaugural Lecture published by Éditions Fayard and online at

• The video of the Inaugural Lecture is available online at, on the professor's page.

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Gérard BERRY, « The Informatics of Time and Events », La lettre du Collège de France [En ligne], 8 | mars 2014, mis en ligne le 01 avril 2015, consulté le 22 février 2018. URL :

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Gérard BERRY

Algorithms, Machines and Languagesfr

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