ILLC-LIRa

illc-lira@list.uva.nl

1 participants
582 discussions

LIRa session: Krisztina Fruzsa (tomorrow, Thursday, 9 June 16:30)
by LIRa Seminar 08 Jun '22

08 Jun '22

Dear all, We will have our next LIRa session tomorrow, on Thursday, 9 June 16:30. Please use our recurring zoom link: https://uva-live.zoom.us/j/88142993494?pwd=d1BsQWR4T2UyK0Job29YNThjaGRkUT09 (Meeting ID: 881 4299 3494, Passcode: 352984) You can find the details of the talk below. Speaker: Krisztina Fruzsa (TU Wien) Date and Time: Thursday, June 9th 2022, 16:30-18:00, Amsterdam time. Venue: online. Title: New hope for epistemic reasoning in byzantine fault-tolerant distributed systems. Abstract. The epistemic approach to the study of various models of distributed systems has shown to be fruitful over the last three decades. In this talk, I will present some of the results in the area w.r.t. the byzantine fault-tolerant model. By extending Fagin et al.’s classic runs-and-systems framework, we have developed a comprehensive framework that also allows modelling misbehaviours of byzantine agents. In this extended framework, we prove the so-called Brain-in-a-Vat Lemma (formalizing the brain-in-a-vat scenario), one of our central results. In this talk we will take a closer look at this result to see how using its various knowledge limitations can be represented in the logical language. We will also take a look at some of our most recent results on the topic, one of them being an alternative axiomatization of the so-called hope modality that has been introduced in the context of epistemic analysis of byzantine fault-tolerant systems. We will see that, essentially, hope can be described using a standard KB4_n system. We will also see how we can combine KB4_n hope modalities with S5_n knowledge modalities in a joint logic enriched with both common hope and common knowledge. Interestingly, in the corresponding logics some of the main properties of the above-mentioned systems such as the bound on the maximal number of byzantine faulty agents and the brain-in-a-vat related properties become frame-characterizable. Hope to see you there! The LIRa team

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LIRa session: Krisztina Fruzsa (Thursday, 9 June 16:30)
by LIRa Seminar 05 Jun '22

05 Jun '22

Dear all, We will have our next LIRa session on Thursday, 9 June 16:30. Please use our recurring zoom link: https://uva-live.zoom.us/j/88142993494?pwd=d1BsQWR4T2UyK0Job29YNThjaGRkUT09 (Meeting ID: 881 4299 3494, Passcode: 352984) You can find the details of the talk below. Speaker: Krisztina Fruzsa (TU Wien) Date and Time: Thursday, June 9th 2022, 16:30-18:00, Amsterdam time. Venue: online. Title: New hope for epistemic reasoning in byzantine fault-tolerant distributed systems. Abstract. The epistemic approach to the study of various models of distributed systems has shown to be fruitful over the last three decades. In this talk, I will present some of the results in the area w.r.t. the byzantine fault-tolerant model. By extending Fagin et al.’s classic runs-and-systems framework, we have developed a comprehensive framework that also allows modelling misbehaviours of byzantine agents. In this extended framework, we prove the so-called Brain-in-a-Vat Lemma (formalizing the brain-in-a-vat scenario), one of our central results. In this talk we will take a closer look at this result to see how using its various knowledge limitations can be represented in the logical language. We will also take a look at some of our most recent results on the topic, one of them being an alternative axiomatization of the so-called hope modality that has been introduced in the context of epistemic analysis of byzantine fault-tolerant systems. We will see that, essentially, hope can be described using a standard KB4_n system. We will also see how we can combine KB4_n hope modalities with S5_n knowledge modalities in a joint logic enriched with both common hope and common knowledge. Interestingly, in the corresponding logics some of the main properties of the above-mentioned systems such as the bound on the maximal number of byzantine faulty agents and the brain-in-a-vat related properties become frame-characterizable. Hope to see you there! The LIRa team

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LIRa Session: Gregor Behnke (tomorrow, Thursday, 2 June 16:30)
by LIRa Seminar 01 Jun '22

01 Jun '22

Dear all, We will have our next LIRa session tomorrow, on Thursday, 2 June 16:30. Please use our recurring zoom link: https://uva-live.zoom.us/j/88142993494?pwd=d1BsQWR4T2UyK0Job29YNThjaGRkUT09 (Meeting ID: 881 4299 3494, Passcode: 352984) You can find the details of the talk below. Speaker: Gregor Behnke (ILLC, University of Amsterdam) Date and Time: Thursday, June 2nd 2022, 16:30-18:00, Amsterdam time. Venue: online. Title: Planning with Temporally extended Goals Abstract. Planning asks to find a sequence of actions that will lead to achieving a given objective. Traditionally, this means that we are given an initial state (in terms of facts over some function-free first-order logic), (first-order) actions that can modify the state, and a goal state. This goal state is described in terms of a set of facts that we want to achieve simultaneously in the last state after executing the whole plan. In some scenarios this simple definition of the objective as a single goal state does not suffice. For example, we might want to describe that we shall first achieve objective A and only afterwards B, or that we want to achieve A without ever achieving B in the mean time. Further one might also want to describe infinite behaviour, i.e., a plan for running a factory machine indefinitely. For this purpose, the description of the objective can be formulated using Temporal Logic -- and are then called "Temporally Extended Goals". In the talk, I will give a brief introduction into planning. I will then turn to the way that temporally extended goals are usually described in planning and discuss the connection of this description language with Linear Temporal Logic. Lastly, I will give a brief overview of the possible ways to integrate Temporally Extended Goals into the planning process. Hope to see you there! The LIRa team

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LIRa Session: Gregor Behnke (Thursday, 2 June 16:30)
by LIRa Seminar 27 May '22

27 May '22

Dear all, We will have our next LIRa session on Thursday, 2 June 16:30. Please use our recurring zoom link: https://uva-live.zoom.us/j/88142993494?pwd=d1BsQWR4T2UyK0Job29YNThjaGRkUT09 (Meeting ID: 881 4299 3494, Passcode: 352984) You can find the details of the talk below. Speaker: Gregor Behnke (ILLC, University of Amsterdam) Date and Time: Thursday, June 2nd 2022, 16:30-18:00, Amsterdam time. Venue: online. Title: Planning with Temporally extended Goals Abstract. Planning asks to find a sequence of actions that will lead to achieving a given objective. Traditionally, this means that we are given an initial state (in terms of facts over some function-free first-order logic), (first-order) actions that can modify the state, and a goal state. This goal state is described in terms of a set of facts that we want to achieve simultaneously in the last state after executing the whole plan. In some scenarios this simple definition of the objective as a single goal state does not suffice. For example, we might want to describe that we shall first achieve objective A and only afterwards B, or that we want to achieve A without ever achieving B in the mean time. Further one might also want to describe infinite behaviour, i.e., a plan for running a factory machine indefinitely. For this purpose, the description of the objective can be formulated using Temporal Logic -- and are then called "Temporally Extended Goals". In the talk, I will give a brief introduction into planning. I will then turn to the way that temporally extended goals are usually described in planning and discuss the connection of this description language with Linear Temporal Logic. Lastly, I will give a brief overview of the possible ways to integrate Temporally Extended Goals into the planning process. Hope to see you there! The LIRa team

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LIRa session: Paul Egré (tomorrow, Thursday, 19 May 16:30)
by LIRa Seminar 18 May '22

18 May '22

Dear all, We will have our next LIRa session tomorrow, on Thursday, 19 May 16:30. Please use our recurring zoom link: https://uva-live.zoom.us/j/88142993494?pwd=d1BsQWR4T2UyK0Job29YNThjaGRkUT09 (Meeting ID: 881 4299 3494, Passcode: 352984) You can find the details of the talk below. Speaker: Paul Egré (École Normale Supérieure) Date and Time: Thursday, May 19th 2022, 16:30-18:00, Amsterdam time. Venue: online. Title: On the optimality of vagueness Abstract. What is the function of vagueness in language? Vagueness is often viewed as a deficiency, but it has also been recognized as a mechanism of prudence and error minimization (Channell 1994, Krifka 2007, van Deemter 2009). The leading hypothesis in this paper is that in contexts in which a cooperative speaker is not perfectly informed about the world, the use of vague expressions can offer an optimal tradeoff between truthfulness (Gricean Quality) and informativeness (Gricean Quantity). Focusing on expressions of approximation such as ``around'', which are semantically vague, it is shown that they allow the speaker to convey indirect probabilistic information, in a way that can give the listener a more accurate representation of the information available to the speaker than *any* more precise expression would (intervals of the form ``between''). The paper presents and develops a probabilistic account of the meaning of "around" to substantiate this hypothesis, in the wake of recent work done in the field of Bayesian pragmatics (Lassiter and Goodman 2017, Goodman and Stuhlmüller 2013). I will discuss some philosophical implications of the account, in particular to revisit a debate between C. Wright and T. Williamson regarding the epistemic conception of approximation expressions such as "around" and of vague expressions more broadly (Wright 1995). Joint work with Benjamin Spector, Adele Mortier, Steven Verheyen. Hope to see you there! The LIRa team

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LIRa session: Paul Egré (Thursday, 19 May 16:30)
by LIRa Seminar 13 May '22

13 May '22

Dear all, We will have our next LIRa session on Thursday, 19 May 16:30. Please use our recurring zoom link: https://uva-live.zoom.us/j/88142993494?pwd=d1BsQWR4T2UyK0Job29YNThjaGRkUT09 (Meeting ID: 881 4299 3494, Passcode: 352984) You can find the details of the talk below. Speaker: Paul Egré (École Normale Supérieure) Date and Time: Thursday, May 19th 2022, 16:30-18:00, Amsterdam time. Venue: online. Title: On the optimality of vagueness Abstract. What is the function of vagueness in language? Vagueness is often viewed as a deficiency, but it has also been recognized as a mechanism of prudence and error minimization (Channell 1994, Krifka 2007, van Deemter 2009). The leading hypothesis in this paper is that in contexts in which a cooperative speaker is not perfectly informed about the world, the use of vague expressions can offer an optimal tradeoff between truthfulness (Gricean Quality) and informativeness (Gricean Quantity). Focusing on expressions of approximation such as ``around'', which are semantically vague, it is shown that they allow the speaker to convey indirect probabilistic information, in a way that can give the listener a more accurate representation of the information available to the speaker than *any* more precise expression would (intervals of the form ``between''). The paper presents and develops a probabilistic account of the meaning of "around" to substantiate this hypothesis, in the wake of recent work done in the field of Bayesian pragmatics (Lassiter and Goodman 2017, Goodman and Stuhlmüller 2013). I will discuss some philosophical implications of the account, in particular to revisit a debate between C. Wright and T. Williamson regarding the epistemic conception of approximation expressions such as "around" and of vague expressions more broadly (Wright 1995). Joint work with Benjamin Spector, Adele Mortier, Steven Verheyen. Hope to see you there! The LIRa team

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LIRa related event: VvL Logic at Large public lecture with Joel David Hamkins on 31 May 2022 - registration open now
by LIRa Seminar 12 May '22

12 May '22

Dear all, We would like to draw your attention to the following event which might also be interesting for the LIRa audience. kind regards, the LIRa team ---- *Logic at Large Lecture 2022* The Dutch Association for Logic and Philosophy of the Exact Sciences (VvL) is happy to announce the Logic at Large Lecture 2022 aimed at a general audience. It will take place on *31 May 2022* (16:00-19:00). We are pleased to announce that Professor *Joel David Hamkins* (University of Notre Dame) will give a public lecture entitled "Infinite Games, Frivolities of the Gods" (see abstract below). The event will take place online using Zoom and will be concluded by a social gathering on the virtual platform Gather.Town. Registration is free, but necessary to receive links to Zoom and Gather.Town. For registration and more information, please visit: https://verenigingvoorlogica.nl/en/Activiteiten/VvL-Logic-at-Large-Lectures/ *Programme*: 16:00-16:30 Virtual arrival and informal discussions 16:30-18:00 Public lecture by Joel D. Hamkins (Notre Dame University) including discussion 18:00-19:00 Social Event on Gather.town Speaker: Joel David Hamkins (University of Notre Dame) Title: "Infinite Games, Frivolities of the Gods" Abstract: Many familiar finite games admit natural infinitary analogues, which often highlight intriguing issues in infinite game theory. Shall we have a game of infinite chess? Or how about infinite draughts, infinite Hex, infinite Go, infinite Wordle, or infinite Sudoku? Let me introduce these games and use them to illustrate various fascinating concepts in the theory of infinite games. ----

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LIRa Session: Rineke Verbrugge (tomorrow, Thursday, 12 May 16:30)
by LIRa Seminar 11 May '22

11 May '22

Dear all, We will have our next LIRa session tomorrow, on Thursday, 12 May 16:30. Please use our recurring zoom link: https://uva-live.zoom.us/j/88142993494?pwd=d1BsQWR4T2UyK0Job29YNThjaGRkUT09 (Meeting ID: 881 4299 3494, Passcode: 352984) You can find the details of the talk below. Speaker: Rineke Verbrugge (University of Groningen) Date and Time: Thursday, May 12th 2022, 16:30-18:00, Amsterdam time. Venue: online. Title: Effectiveness of higher-order theory of mind in competitive, cooperative and mixed-motive situations Abstract. When engaging in intelligent interaction, people rely on their ability to reason about other people's mental states, including goals, intentions, and beliefs. This theory of mind ability allows them to more easily understand, predict, and manipulate the behavior of others. People can use their theory of mind recursively, which allows them to understand second-order attributions such as "Alice believes that Bob does not know that she wrote a novel under pseudonym". This ability is unique to humans: animals may or may not exhibit some forms of first-order theory of mind, but definitely no higher orders. Using agent-based modeling, Harmen de Weerd, Bart Verheij and I have shown that higher-order theory of mind reasoning can be useful across competitive, cooperative, and mixed-motive settings. In this lecture, we discuss these results and we cast a new light on mixed-motive situations by investigating how the predictability of the environment influences the effectiveness of higher-order theory of mind. Our results show that the benefit of higher-order theory of mind reasoning depends on the predictability of the environment. We consider agent-based simulations in repeated one-shot negotiations in the negotiation game 'Colored Trails'. When this environment is highly predictable, agents obtain little benefit from theory of mind reasoning. However, if the environment has more observable features that change over time, agents without the ability to use theory of mind experience more difficulties predicting the behavior of others accurately. This in turn allows theory of mind agents to obtain higher scores in these more dynamic environments. These results suggest that the human-specific ability for higher-order theory of mind reasoning may have evolved to allow us to survive in more complex and unpredictable environments. Hope to see you there! The LIRa team

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LIRa Session: Rineke Verbrugge (Thursday, 12 May 16:30)
by LIRa Seminar 09 May '22

09 May '22

Dear all, We will have our next LIRa session on Thursday, 12 May 16:30. Please use our recurring zoom link: https://uva-live.zoom.us/j/88142993494?pwd=d1BsQWR4T2UyK0Job29YNThjaGRkUT09 (Meeting ID: 881 4299 3494, Passcode: 352984) You can find the details of the talk below. Speaker: Rineke Verbrugge (University of Groningen) Date and Time: Thursday, May 12th 2022, 16:30-18:00, Amsterdam time. Venue: online. Title: Effectiveness of higher-order theory of mind in competitive, cooperative and mixed-motive situations Abstract. When engaging in intelligent interaction, people rely on their ability to reason about other people’s mental states, including goals, intentions, and beliefs. This theory of mind ability allows them to more easily understand, predict, and manipulate the behavior of others. People can use their theory of mind recursively, which allows them to understand second-order attributions such as “Alice believes that Bob does not know that she wrote a novel under pseudonym”. This ability is unique to humans: animals may or may not exhibit some forms of first-order theory of mind, but definitely no higher orders. Using agent-based modeling, Harmen de Weerd, Bart Verheij and I have shown that higher-order theory of mind reasoning can be useful across competitive, cooperative, and mixed-motive settings. In this lecture, we discuss these results and we cast a new light on mixed-motive situations by investigating how the predictability of the environment influences the effectiveness of higher-order theory of mind. Our results show that the benefit of higher-order theory of mind reasoning depends on the predictability of the environment. We consider agent-based simulations in repeated one-shot negotiations in the negotiation game 'Colored Trails'. When this environment is highly predictable, agents obtain little benefit from theory of mind reasoning. However, if the environment has more observable features that change over time, agents without the ability to use theory of mind experience more difficulties predicting the behavior of others accurately. This in turn allows theory of mind agents to obtain higher scores in these more dynamic environments. These results suggest that the human-specific ability for higher-order theory of mind reasoning may have evolved to allow us to survive in more complex and unpredictable environments. Hope to see you there! The LIRa team

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LIRa session: Marianna Girlando (tomorrow, Thursday, 28 April 16:30)
by LIRa Seminar 27 Apr '22

27 Apr '22

Dear all, We will have our next LIRa session tomorrow, on Thursday, 28 April 16:30. Please use our recurring zoom link: https://uva-live.zoom.us/j/88142993494?pwd=d1BsQWR4T2UyK0Job29YNThjaGRkUT09 (Meeting ID: 881 4299 3494, Passcode: 352984) You can find the details of the talk below. Speaker: Marianna Girlando (University of Birmingham) Date and Time: Thursday, April 28th 2022, 16:30-18:00, Amsterdam time. Venue: online. Title: Counterfactuals, comparative plausibility and neighbourhoods: from semantics to automated theorem proving. Abstract. Conditional logics can be used to express counterfactuals (Lewis) or forms of non-monotonic reasoning (Burgess). They are defined by adding to classical propositional logic a two-places modality, the conditional operator. Semantics for conditional logics can be uniformly defined in terms of neighbourhood semantics, generalising Lewis' sphere models. In this talk, I will show the relations between the conditional operator and a weaker modal operator, the comparative plausibility, that I will use to define analytic proof systems for some of the stronger logics in the conditional family. Then, I will illustrate how these proof systems can be implemented to design automated reasoning tools for conditional logics. This talk is based on joint work with Bjoern Lellmann, Nicola Olivetti, Gian Luca Pozzato and Stefano Pesce. The theorem prover is available here: http://193.51.60.97:8000/tuclever/ Hope to see you there! The LIRa team

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