Ghislain Fourny

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• Dr. sc. ETH Zürich
• Senior Scientist at ETH Zurich

This paper introduces a new solution concept for non-cooperative games in normal form with no ties and pure strategies: the Perfectly Transparent Equilibrium. The players are rational in all possible worlds and know each other’s strategies in all possible worlds – which, together, we refer to as Perfect Prediction. The anticipation of a player’s de...

This paper contributes a new class of games called spacetime games with perfect information. In spacetime games, the agents make decisions at various positions in Minkowski spacetime. Spacetime games can be seen as the least common denominator of strategic games on the one hand, and dynamic games with perfect information on the other hand. Indeed,...

This paper introduces Rumble, a query execution engine for large, heterogeneous, and nested collections of JSON objects built on top of Apache Spark. While data sets of this type are more and more wide-spread, most existing tools are built around a tabular data model, creating an impedance mismatch for both the engine and the query interface. In co...

We suggest to look at quantum measurement outcomes not through the lens of probability theory, but instead through decision theory. We introduce an original game-theoretical framework, model and algorithmic procedure where measurement scenarios are multiplayer games with a structure all observers agree on. Measurement axes and, newly, measurement o...

We show that causal contextuality scenarios are equivalent to a subset of the formerly published spacetime games, which generalize game theory to decisions arbitrarily located in Minkowski spacetime. This insight leads to certain constructs and proofs being shorter, simpler, and more intuitive when expressed in the spacetime game framework than in...

This study proposes an AI-supported framework for extending quantum theory by recasting quantum experiments as games between measurers and Nature. Inspired by Einstein’s scepticism of quantum theory’s inherent randomness, the approach leverages artificial intelligence to infer optimal game rewards (or “payoffs”), thereby reproducing expected probab...

This is the textbook of my Big Data course at ETH Zurich. It is work in progress. Latest update March 4 2025 including a new started chapter on data cubes. A list of recent changes and fixes (usually small fixes) is available in the last Chapter to avoid having to reread everything. Major changes in the second edition: coverage of key-value stores...

In 2019, we introduced games in Minkowski spacetime as a generalization of game theory to special relativity that subsumes games in normal form (spacelike separation) and games in extensive form (timelike separation). Many concepts of the game theory literature, including Nash equilibria and flattened strategic forms, naturally extend to spacetime...

In the domain of high-energy physics (HEP), general-purpose query languages have found little adoption in analysis. This is surprising regarding SQL-based systems, as HEP data analysis matches SQL’s processing model well: the data is fully structured and makes use of predominantly standard operators. To better understand the situation, we select si...

This note proposes a paradigm and coordinate system that extends flat, four-dimensional Minkowski spacetime to a broader framework that identifies an event not only in space and in time, but also in terms of possible world, with a third category of coordinates called ``hap'' modelling contingency and counterfactuals. Semantically, hap is based on a...

Lakehouse systems have reached in the past few years unprecedented size and heterogeneity and have been embraced by many industry players. However, they are often difficult to use as they lack the declarative language and optimization possibilities of relational engines. This paper introduces RumbleML, a high-level, declarative library integrated i...

We suggest to look at quantum measurement outcomes not through the lens of probability theory, but instead through decision theory. We introduce an original game-theoretical framework, model and algorithmic procedure where measurement scenarios are multiplayer games with an observer-independent structure. Measurement axes and, newly, measurement ou...

In the domain of high-energy physics (HEP), query languages in general and SQL in particular have found limited acceptance. This is surprising since HEP data analysis matches the SQL model well: the data is fully structured and queried using mostly standard operators. To gain insights on why this is the case, we perform a comprehensive analysis of...

In this letter, we point to three widely accepted challenges that the quantum theory, quantum information, and quantum foundations communities are currently facing: indeterminism, the semantics of conditional probabilities, and the spooky action at a distance. We argue that these issues are fundamentally rooted in conflations commonly made between...

In this letter, we point to three widely accepted challenges that the quantum theory, quantum information, and quantum foundations communities are currently facing: indeterminism, the semantics of conditional probabilities, and the spooky action at a distance. We argue that these issues are fundamentally rooted in conflations commonly made between...

Query languages in general and SQL in particular are arguably one of the most successful programming interfaces. Yet, in the domain of high-energy physics (HEP), they have found limited acceptance. This is surprising since data analysis in HEP matches the SQL model well: it is fully structured data queried using combinations of selections, projecti...

This dataset includes 204,350,000 games in normal form played by two agents that have the choice between three strategies each, as well as 100,000 games in normal form played by four agents that have the choice between three strategies each. The games are in general position, i.e., there are no ties between the outcomes for each of the agents. Thes...

This paper introduces Rumble, an engine that executes JSONiq queries on large, heterogeneous and nested collections of JSON objects, leveraging the parallel capabilities of Spark so as to provide a high degree of data independence. The design is based on two key insights: (i) how to map JSONiq expressions to Spark transformations on RDDs and (ii) h...

The non-extensibility of quantum theory into an extended theory with improved predictive power is based on a strong assumption of independent free choice, in which the physicists pick a measurement axis independently of anything that couldn't have been caused by their decision. Independent free choice is also at the core of the Nash equilibrium and...

The assumptions of necessary rationality and necessary knowledge of strategies, also known as perfect prediction, lead to at most one surviving outcome, immune to the knowledge that the players have of them. Solutions concepts implementing this approach have been defined on both dynamic games with perfect information, the Perfect Prediction Equilib...

The Perfectly Transparent Equilibrium is algorithmically defined, for any game in normal form with perfect information and no ties, as the iterated deletion of non-individually-rational strategy profiles until at most one remains. In this paper, we characterize the Perfectly Transparent Equilibrium with adapted Kripke models having necessary ration...

This paper introduces a new solution concept for non-cooperative games in normal form with no ties and pure strategies: the Perfectly Transparent Equilibrium. The players are rational in all possible worlds and know each other's strategies in all possible worlds, which together we refer to as Perfect Prediction. The anticipation of a player's decis...

This paper shows that, for symmetric games in normal form, strategy profiles that satisfy Hofstadter's Superrationality criterion also satisfy both of Halpern's criteria under Common Counterfactual Belief of Rationality: minimax-rationalizability and individual rationality.

The Nash equilibrium paradigm, and Rational Choice Theory in general , rely on agents acting independently from each other. This note shows how this assumption is crucial in the definition of Rational Choice Theory. It explains how a consistent Alternate Rational Choice Theory, as suggested by Jean-Pierre Dupuy, can be built on the exact opposite a...

This paper introduces a binary encoding that supports arbitrarily large, small and precise decimals. It completely preserves information and order. It does not rely on any arbitrary use-case-based choice of calibration and is readily implementable and usable, as is. Finally, it is also simple to explain and understand.

Cell stores provide a relational-like, tabular level of abstraction to business users while leveraging recent database technologies, such as key-value stores and document stores. This allows to scale up and out the efficient storage and retrieval of highly dimensional data. Cells are the primary citizens and exist in different forms, which can be e...

In the framework of finite games in extensive form with perfect information and strict preferences, this paper introduces a new equilibrium concept under the assumption of total transparency: all players share the same knowledge and know as much as an omniscient external observer. In particular, there is common knowledge of the solution of the game...

After 40 years of relational databases and of cohabitation between flat tables and object-oriented programming, a new generation of data stores is emerging. Sometimes referred to as NoSQL, this new generation supports hierarchical, heterogeneous data such as XML, JavaScript Object Notation, and Binary JSON. While the abstract querying primitives of...

With sinking storage costs, it becomes more and more fea-sible, and popular, to retain past versions of documents and data. While undoing changes is worthy, this becomes even more valuable if the data is queryable. Nowadays, there are two widespread version control paradigms: document versioning (SVN, git, etc.) and versioned databases. The former...

As storage-main memory as well as disk-becomes cheaper, the amount of available information is increasing and it is a challenge to organize it. Our broader aim is to provide a unified framework for efficiently versioning and querying data, documents, as well as any kind of semi-structured information between data and documents, which can be stored...

Since the invention of the Web, the browser has become more and more powerful. By now, it is a programming and execution environment in itself. The predominant language to program applications in the browser today is JavaScript. With browsers becoming more powerful, JavaScript has been extended and new layers have been added (e.g., DOM-Sup- port an...

Over the years, the browser has become a complete runtime environment for client-side programs. The main scripting language used towards this purpose is JavaScript, which was designed so as to program the browser. A lot of extensions and new layers have been built on top of it to allow e.g. DOM navigation and manipulation. However, JavaScript has b...