ILLC-LIRa

illc-lira@list.uva.nl

1 participants
582 discussions

CHANGE: room L3.33 in Lab 42 for LIRa session: Hans van Ditmarsch (today, 16:30)
by LIRa Seminar 18 Apr '24

18 Apr '24

Dear all, Please note: The room for the LIRa session today had to be changed. *We will be in room L3.33 in Lab 42.* To attend online, please use our recurring zoom link: https://uva-live.zoom.us/j/89230639823?pwd=YWJuSnJmTDhXcWhmd1ZkeG5zb0o5UT09 (Meeting ID: 892 3063 9823, Passcode: 421723) You can find the details of the talk below. Speaker: Hans van Ditmarsch (University of Toulouse, CNRS, IRIT) Date and Time: Thursday, April 18th 2024, 16:30-18:00 Venue: room L3.33 in Lab 42 and online. Title: Distributed Knowledge Revisited. Abstract. We review the history and some recent work on what is known since the 1990s as distributed knowledge. Such epistemic group notions are currently getting more and more attention both from the modal logical community and from distributed computing, in various settings with communicating processes or agents. The typical intuition is that if a knows p, and b knows that p implies q, then together they know that q: they have distributed knowledge of q. In order to get to know q they need to share their knowledge. We will discuss: (i) the complete axiomatization, (ii) why not everything that is distributed knowledge can become common knowledge, (iii) the notion of collective bisimulation, (iv) distributed knowledge for infinitely many agents, (v) the novel update called resolving distributed knowledge and some variations (and its incomparable update expressivity to action models), (vi) distributed knowledge that is stronger than the sum of individual knowledge (where the relation for the group of agents is strictly contained in their intersection), (vii) common distributed knowledge and its topological interpretations, (viii) dynamic distributed knowledge, a version of the semantics ensuring that what is distributed knowledge becomes common knowledge, and the axiomatization, expressivity and bisimulation characterization of this logic. Hope to see you there! The LIRa team

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LIRa session: Hans van Ditmarsch (tomorrow, Thursday, 18 April 16:30)
by LIRa Seminar 17 Apr '24

17 Apr '24

Dear all, We will have our next LIRa session tomorrow, on Thursday, 18 April 16:30. To attend online, please use our recurring zoom link: https://uva-live.zoom.us/j/89230639823?pwd=YWJuSnJmTDhXcWhmd1ZkeG5zb0o5UT09 (Meeting ID: 892 3063 9823, Passcode: 421723) You can find the details of the talk below. Speaker: Hans van Ditmarsch (University of Toulouse, CNRS, IRIT) Date and Time: Thursday, April 18th 2024, 16:30-18:00 Venue: ILLC seminar room F1.15 in Science Park 107 and online. Title: Distributed Knowledge Revisited. Abstract. We review the history and some recent work on what is known since the 1990s as distributed knowledge. Such epistemic group notions are currently getting more and more attention both from the modal logical community and from distributed computing, in various settings with communicating processes or agents. The typical intuition is that if a knows p, and b knows that p implies q, then together they know that q: they have distributed knowledge of q. In order to get to know q they need to share their knowledge. We will discuss: (i) the complete axiomatization, (ii) why not everything that is distributed knowledge can become common knowledge, (iii) the notion of collective bisimulation, (iv) distributed knowledge for infinitely many agents, (v) the novel update called resolving distributed knowledge and some variations (and its incomparable update expressivity to action models), (vi) distributed knowledge that is stronger than the sum of individual knowledge (where the relation for the group of agents is strictly contained in their intersection), (vii) common distributed knowledge and its topological interpretations, (viii) dynamic distributed knowledge, a version of the semantics ensuring that what is distributed knowledge becomes common knowledge, and the axiomatization, expressivity and bisimulation characterization of this logic. Hope to see you there! The LIRa team

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LIRa session: Hans van Ditmarsch (Thursday, 18 April 16:30)
by LIRa Seminar 12 Apr '24

12 Apr '24

Dear all, We will have our next LIRa session on Thursday, 18 April 16:30. To attend online, please use our recurring zoom link: https://uva-live.zoom.us/j/89230639823?pwd=YWJuSnJmTDhXcWhmd1ZkeG5zb0o5UT09 (Meeting ID: 892 3063 9823, Passcode: 421723) You can find the details of the talk below. Speaker: Hans van Ditmarsch (University of Toulouse, CNRS, IRIT) Date and Time: Thursday, April 18th 2024, 16:30-18:00 Venue: ILLC seminar room F1.15 in Science Park 107 and online. Title: Distributed Knowledge Revisited. Abstract. We review the history and some recent work on what is known since the 1990s as distributed knowledge. Such epistemic group notions are currently getting more and more attention both from the modal logical community and from distributed computing, in various settings with communicating processes or agents. The typical intuition is that if a knows p, and b knows that p implies q, then together they know that q: they have distributed knowledge of q. In order to get to know q they need to share their knowledge. We will discuss: (i) the complete axiomatization, (ii) why not everything that is distributed knowledge can become common knowledge, (iii) the notion of collective bisimulation, (iv) distributed knowledge for infinitely many agents, (v) the novel update called resolving distributed knowledge and some variations (and its incomparable update expressivity to action models), (vi) distributed knowledge that is stronger than the sum of individual knowledge (where the relation for the group of agents is strictly contained in their intersection), (vii) common distributed knowledge and its topological interpretations, (viii) dynamic distributed knowledge, a version of the semantics ensuring that what is distributed knowledge becomes common knowledge, and the axiomatization, expressivity and bisimulation characterization of this logic. Hope to see you there! The LIRa team

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LIRa session: Alexandru Baltag (tomorrow, Thursday, 11 April 17:00)
by LIRa Seminar 10 Apr '24

10 Apr '24

Dear all, We will have our next LIRa session tomorrow, on Thursday, 11 April 17:00. To attend online, please use our recurring zoom link: https://uva-live.zoom.us/j/89230639823?pwd=YWJuSnJmTDhXcWhmd1ZkeG5zb0o5UT09 (Meeting ID: 892 3063 9823, Passcode: 421723) You can find the details of the talk below. Speaker: Alexandru Baltag (ILLC, Amsterdam) Date and Time: Thursday, April 11th 2024, 17:00-18:30 (note unusual time!) Venue: F1.15 and online. Title: Simple Recursion Laws for DEL and its extensions Abstract. There are two standard approaches to axiomatizing full DEL (with common knowledge and arbitrary events): (a) directly axiomatizing the dynamic logic, using ``Dynamic Induction" rules; and (b) extending the static base to Epistemic PDL (E-PDL) and reducing DEL to it using Recursion/Reduction axioms. Each of these options has its disadvantage: option (a) uses rather complex and non-standard rules, and the completeness proof is rather convoluted; while (b) uses a simple logic with a well-known axiomatization for the static logic, but the dynamic recursion/reduction axioms are extremely complex and opaque (-indeed, they take several pages of notations just to state). The same dilemma occurs again when DEL is extended to data-exchange events, in which agents access other agents' full information database: in the case, the relevant static base is Group Epistemic PDL (GE-PDL, i.e. PDL built on top of distributed knowledge modalities for groups of agents), but the relevant recursion laws become even more impenetrable. In this talk, I take a fresh look at the minimal static base needed for obtaining reductions for DEL and its mentioned extensions. By looking at recursion axioms as systems of equations, we are lead to extend the static language with polyadic conditionals, that are obtained as solutions to such systems of equations. Epistemically, these polyadic modalities capture various complex levels of conditional group knowledge, so they can be considered as generalizations of the common knowledge operator. As such, they can be given a transparent axiomatization and a filtration-based completeness proof, obtained by generalizing the corresponding axioms and proof for common knowledge. More importantly, the recursion/reduction laws become extremely simple and elegant. Even better, the same program can be applied to the extension of DEL with data-exchange events. This talk is based on joint work: reference [1], joint with Johan van Benthem; and [2], joint with Sonja Smets; and it also relates to older joint work [3]. REFERENCES: [1] A. Baltag & J. van Benthem: Updates, Generalized p-Morphisms, and (Co-)Recursive Equations. In J. van Benthem & F. Liu (eds), *Graph Games and Logic Design - Recent developments and further directions*, Springer 2024 to appear. [2] A. Baltag & S. Smets: Logics for Data Exchange and Communication. Submitted to AiML 2024. [3] A. Baltag and S. Smets: Learning what Others Know. In L. Kovacs and E. Albert (eds.), *LPAR23 proceedings of the International Conference on Logic for Programming AI and Reasoning*, EPiC Series in Computing, Volume 73, pp 90-110, 2020. https://doi.org/10.29007/plm4 Hope to see you there! The LIRa team

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LIRa session: Alexandru Baltag (Thursday, 11 April 17:00 - unusual time - on location and online)
by LIRa Seminar 05 Apr '24

05 Apr '24

Dear all, We will have our next LIRa session on Thursday, 11 April 17:00. This session will be on location and online. To attend via zoom please use our recurring link: https://uva-live.zoom.us/j/89230639823?pwd=YWJuSnJmTDhXcWhmd1ZkeG5zb0o5UT09 (Meeting ID: 892 3063 9823, Passcode: 421723) You can find the details of the talk below. Speaker: Alexandru Baltag (ILLC, Amsterdam) Date and Time: Thursday, April 11th 2024, 17:00-18:30 (note the unusual time!) Venue: F1.15 and online. Title: Simple Recursion Laws for DEL and its extensions Abstract. There are two standard approaches to axiomatizing full DEL (with common knowledge and arbitrary events): (a) directly axiomatizing the dynamic logic, using ``Dynamic Induction" rules; and (b) extending the static base to Epistemic PDL (E-PDL) and reducing DEL to it using Recursion/Reduction axioms. Each of these options has its disadvantage: option (a) uses rather complex and non-standard rules, and the completeness proof is rather convoluted; while (b) uses a simple logic with a well-known axiomatization for the static logic, but the dynamic recursion/reduction axioms are extremely complex and opaque (-indeed, they take several pages of notations just to state). The same dilemma occurs again when DEL is extended to data-exchange events, in which agents access other agents' full information database: in the case, the relevant static base is Group Epistemic PDL (GE-PDL, i.e. PDL built on top of distributed knowledge modalities for groups of agents), but the relevant recursion laws become even more impenetrable. In this talk, I take a fresh look at the minimal static base needed for obtaining reductions for DEL and its mentioned extensions. By looking at recursion axioms as systems of equations, we are lead to extend the static language with polyadic conditionals, that are obtained as solutions to such systems of equations. Epistemically, these polyadic modalities capture various complex levels of conditional group knowledge, so they can be considered as generalizations of the common knowledge operator. As such, they can be given a transparent axiomatization and a filtration-based completeness proof, obtained by generalizing the corresponding axioms and proof for common knowledge. More importantly, the recursion/reduction laws become extremely simple and elegant. Even better, the same program can be applied to the extension of DEL with data-exchange events. This talk is based on joint work: reference [1], joint with Johan van Benthem; and [2], joint with Sonja Smets; and it also relates to older joint work [3]. REFERENCES: [1] A. Baltag & J. van Benthem: Updates, Generalized p-Morphisms, and (Co-)Recursive Equations. In J. van Benthem & F. Liu (eds), *Graph Games and Logic Design - Recent developments and further directions*, Springer 2024 to appear. [2] A. Baltag & S. Smets: Logics for Data Exchange and Communication. Submitted to AiML 2024. [3] A. Baltag and S. Smets: Learning what Others Know. In L. Kovacs and E. Albert (eds.), *LPAR23 proceedings of the International Conference on Logic for Programming AI and Reasoning*, EPiC Series in Computing, Volume 73, pp 90-110, 2020. https://doi.org/10.29007/plm4 Hope to see you there! The LIRa team

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LIRa session: Tim French (tomorrow, Wednesday, 27 March 16:30)
by LIRa Seminar 26 Mar '24

26 Mar '24

Dear all, We will have our next LIRa session tomorrow, on Wednesday, 27 March 16:30. To attend online, please use our recurring zoom link: https://uva-live.zoom.us/j/89230639823?pwd=YWJuSnJmTDhXcWhmd1ZkeG5zb0o5UT09 (Meeting ID: 892 3063 9823, Passcode: 421723) You can find the details of the talk below. Speaker: Tim French (The University of Western Australia) Date and Time: Wednesday, March 27th 2024, 16:30-18:00 (PLEASE NOTE the unusual day of the week) Venue: ILLC seminar room F1.15 in Science Park 107 and online. Title: Aleatoric Reasoning: The World as an Urn of Marbles Abstract. Imagine the world, and all that we experience as being capriciously random like an urn of marbles. There is no causality or meaning; just random chance. Will it rain today? We draw a marble from the urn and if it is blue, it will rain. Will it snow today? We draw three marbles from the urn and if they are all blue it will snow. Such a world can be succinctly modelled by a domain of marbles (a probability space), and a set of Boolean predicates defined over the domain of marbles. By providing a language where complex propositions are defined over the set of predicate atoms, correlation emerges and reason may be applied. This is not ontological reason, or scientific causality, but rather the pure epistemic bias that comes from observation. This language provides a simple model of belief and knowledge: an agent's beliefs are given by the probability space of marbles in an urn, conditioned on experience; and an agent's knowledge is communicated a priori, as the form of equivalences among complex propositions, creating correspondences among the world's inherent randomness. In this talk we will discuss and present and language for building complex propositions from these aleatoric atoms, and define a logic of identity among the propositions. We will demonstrate some basic applications of the logic, including some interesting proof theoretic and expressivity results. We will then explore the process of learning in an aleatoric world, using some convenient mathematical results to show how conditioning can be applied when observations correspond to complex aleatoric propositions. This allows agents to refine their beliefs according to experience and knowledge, and gain a meaningful understanding of the aleatoric world. Hope to see you there! The LIRa team

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LIRa session: Tim French (Wednesday, 27 March 16:30)
by LIRa Seminar 21 Mar '24

21 Mar '24

Dear all, We will have our next LIRa session on Wednesday, 27 March 16:30. PLEASE NOTE the unusual day of the week! This will be a hybrid session. To attend online, please use our recurring zoom link: https://uva-live.zoom.us/j/89230639823?pwd=YWJuSnJmTDhXcWhmd1ZkeG5zb0o5UT09 (Meeting ID: 892 3063 9823, Passcode: 421723) You can find the details of the talk below. Speaker: Tim French (The University of Western Australia) Date and Time: Wednesday, March 27th 2024, 16:30-18:00 Venue: ILLC seminar room F1.15 in Science Park 107 and online. Title: Aleatoric Reasoning: The World as an Urn of Marbles Abstract. Imagine the world, and all that we experience as being capriciously random like an urn of marbles. There is no causality or meaning; just random chance. Will it rain today? We draw a marble from the urn and if it is blue, it will rain. Will it snow today? We draw three marbles from the urn and if they are all blue it will snow. Such a world can be succinctly modelled by a domain of marbles (a probability space), and a set of Boolean predicates defined over the domain of marbles. By providing a language where complex propositions are defined over the set of predicate atoms, correlation emerges and reason may be applied. This is not ontological reason, or scientific causality, but rather the pure epistemic bias that comes from observation. This language provides a simple model of belief and knowledge: an agent's beliefs are given by the probability space of marbles in an urn, conditioned on experience; and an agent's knowledge is communicated a priori, as the form of equivalences among complex propositions, creating correspondences among the world's inherent randomness. In this talk we will discuss and present and language for building complex propositions from these aleatoric atoms, and define a logic of identity among the propositions. We will demonstrate some basic applications of the logic, including some interesting proof theoretic and expressivity results. We will then explore the process of learning in an aleatoric world, using some convenient mathematical results to show how conditioning can be applied when observations correspond to complex aleatoric propositions. This allows agents to refine their beliefs according to experience and knowledge, and gain a meaningful understanding of the aleatoric world. Hope to see you there! The LIRa team

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Correction: ONLINE ONLY - LIRa session: Daniel Greco (Today, 21 March 16:30)
by LIRa Seminar 21 Mar '24

21 Mar '24

Dear all, Our previous email was unfortunately contradictory. To clarify: the session today will be ONLINE ONLY, not hybrid. Hence please use our recurring zoom link: https://uva-live.zoom.us/j/89230639823?pwd=YWJuSnJmTDhXcWhmd1ZkeG5zb0o5UT09 (Meeting ID: 892 3063 9823, Passcode: 421723) You can find the details of the talk below. Speaker: Daniel Greco (Yale University) Date and Time: Thursday, March 21st 2024, 16:30-18:00 Venue: Online only Title: Idealization in Epistemology Abstract: I’ll present some material from my recently published book, Idealization in Epistemology: A Modest Modeling Approach. After explaining what I mean by “modest” modeling, and why I take it to provide an attractive framework for thinking about epistemology, I’ll apply that framework to two specific debates. First, I’ll consider the objections to Bayesian models of learning that they go wrong in representing the inputs to learning as certain (strict conditionalization), or, even when not certain, as immune to undermining defeat (Jeffrey conditionalization). I'll argue that these objections should trouble us much less once we’re modest modelers. Second, I’ll consider the argument that it’s computationally infeasible for limited agents like us to make extensive use of probabilities in thought. I’ll argue that this argument targets an implausibly immodest vision of the cognitive role of probabilistic thinking. When aimed at an appropriately modest conception of the role of probabilities in both descriptive and normative decision theory, the argument fails. Hope to see you there! The LIRa team

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LIRa session: Daniel Greco (tomorrow, Thursday, 21 March 16:30)
by LIRa Seminar 20 Mar '24

20 Mar '24

Dear all, We will have our next LIRa session tomorrow, on Thursday, 21 March 16:30. This will be a hybrid session. If you want to attend online, please use our recurring zoom link: https://uva-live.zoom.us/j/89230639823?pwd=YWJuSnJmTDhXcWhmd1ZkeG5zb0o5UT09 (Meeting ID: 892 3063 9823, Passcode: 421723) You can find the details of the talk below. Speaker: Daniel Greco (Yale University) Date and Time: Thursday, March 21st 2024, 16:30-18:00 Venue: Online only Title: Idealization in Epistemology Abstract: I’ll present some material from my recently published book, Idealization in Epistemology: A Modest Modeling Approach. After explaining what I mean by “modest” modeling, and why I take it to provide an attractive framework for thinking about epistemology, I’ll apply that framework to two specific debates. First, I’ll consider the objections to Bayesian models of learning that they go wrong in representing the inputs to learning as certain (strict conditionalization), or, even when not certain, as immune to undermining defeat (Jeffrey conditionalization). I'll argue that these objections should trouble us much less once we’re modest modelers. Second, I’ll consider the argument that it’s computationally infeasible for limited agents like us to make extensive use of probabilities in thought. I’ll argue that this argument targets an implausibly immodest vision of the cognitive role of probabilistic thinking. When aimed at an appropriately modest conception of the role of probabilities in both descriptive and normative decision theory, the argument fails. Hope to see you there! The LIRa team

1 0

LIRa session: Daniel Greco (Thursday, 21 March 16:30, online only)
by LIRa Seminar 16 Mar '24

16 Mar '24

Dear all, We will have our next LIRa session on Thursday, 21 March 16:30. This will be an online-only session. To attend please use our recurring zoom link: https://uva-live.zoom.us/j/89230639823?pwd=YWJuSnJmTDhXcWhmd1ZkeG5zb0o5UT09 (Meeting ID: 892 3063 9823, Passcode: 421723) You can find the details of the talk below. Speaker: Daniel Greco (Yale University) Date and Time: Thursday, March 21st 2024, 16:30-18:00 Venue: Online only Title: Idealization in Epistemology Abstract: I’ll present some material from my recently published book, Idealization in Epistemology: A Modest Modeling Approach. After explaining what I mean by “modest” modeling, and why I take it to provide an attractive framework for thinking about epistemology, I’ll apply that framework to two specific debates. First, I’ll consider the objections to Bayesian models of learning that they go wrong in representing the inputs to learning as certain (strict conditionalization), or, even when not certain, as immune to undermining defeat (Jeffrey conditionalization). I'll argue that these objections should trouble us much less once we’re modest modelers. Second, I’ll consider the argument that it’s computationally infeasible for limited agents like us to make extensive use of probabilities in thought. I’ll argue that this argument targets an implausibly immodest vision of the cognitive role of probabilistic thinking. When aimed at an appropriately modest conception of the role of probabilities in both descriptive and normative decision theory, the argument fails. Hope to see you there! The LIRa team

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