Seminar Announcement (A. Novaro)

Don’t miss out on our next seminar of the Logic Lunch series! Next Thursday (April 22nd), Arianna Novaro (ILLC Amsterdam) will talk about Unravelling multi-agent ranked delegations, starting at 12:30. Save the date and join us on Zoom! Please find more information below, and follow us on Twitter and Instagram for more events and activities.

Title: Unravelling multi-agent ranked delegations

Abstract: In this talk, I will present a framework for collective decision-making where the agents have to vote on a given issue, but they can also choose to delegate their vote (if, for instance, they did not have the time or expertise to take a stance on the issue at stake). The agents can express complex delegations, i.e., they can specify a set of trusted delegates and a function–being it a classical voting rule or a propositional formula–to decide their vote, and they can also provide a ranking of preferred delegations. Given these complex delegation ballots, I will present four algorithms that unravel the ballots to get a profile of direct votes, on which the final decision can be taken by using some standard voting rule. In particular, I will discuss both the algorithmic properties and the computational complexity of the four algorithms, for different restrictions on the language of the delegation ballots. This is joint work with Rachael Colley and Umberto Grandi.

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Seminar Announcement (M. Law)

We are happy to announce that on April 8th, Mark Law (Imperial College London) will give the fourth talk of our Logic Lunch seminar series, starting at 12:30. Join us on Zoom at this link! And don’t forget to follow us on Twitter and Instagram to keep up to date with our news and events. Please find more information below:

Title: Logic-based Learning of Answer Set Programs

Abstract: In recent years, non-monotonic Inductive Logic Programming (ILP) has received growing interest. Specifically, several new learning frameworks and algorithms have been introduced for learning under the answer set semantics, allowing the learning of common-sense knowledge involving defaults and exceptions, which are essential aspects of human reasoning.

The first part of this seminar will present recent advances which have extended the theory of ILP and yielded a new collection of algorithms, called ILASP (Inductive Learning of Answer Set Programs), which are able to learn ASP programs consisting of normal rules, choice rules and both hard and weak constraints. Learning such programs allows ILASP to be applied in settings which had previously been outside the scope of ILP. In particular, weak constraints represent preference orderings, and so learning weak constraints allows ILASP to be used for preference learning.

The second part of the talk will present more recent work on a less general but much more scalable approach to learning ASP, called FastLAS. FastLAS is able to solve tasks with hypothesis spaces that are many orders of magnitude larger than those tolerated by ILASP, meaning that it can be applied to a greater range of real-world problems.

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Seminar Announcement (S. Beckers)

Our Logic Lunch Seminar Series continues this week. Sander Beckers (MCMP Munich) will give the next talk on March 25th, starting at 12:30. Save the date and join us on Zoom at this link! Please find more information below, and follow us on Twitter and Instagram to keep up to date!

Title: Causal Sufficiency and Actual Causation

Abstract: Pearl opened the door to formally defining actual causation using causal models. His approach rests on two strategies: first, capturing the widespread intuition that X = x causes Y = y iff X = x is a Necessary Element of a Sufficient Set for Y = y, and second, showing that his definition gives intuitive answers on a wide set of problem cases. This inspired dozens of variations of his definition of actual causation, the most prominent of which are due to Halpern & Pearl. Yet all of them ignore Pearl’s first strategy, and the second strategy taken by itself is unable to deliver a consensus. In this talk I offer a way out by going back to the first strategy: I offer six formal definitions of causal sufficiency and two interpretations of necessity. Combining the two gives twelve new definitions of actual causation. Several interesting results about these definitions and their relation to the various Halpern & Pearl definitions are presented. Afterwards the second strategy is evaluated as well. In order to maximize neutrality, I rely mostly on the examples and intuitions of Halpern & Pearl. One definition comes out as being superior to all others, and is therefore suggested as a new definition of actual causation.

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Seminar Announcement (R. Kuznets)

After a successful first talk given by Fabrizio Riguzzi, our Logic Lunch Seminar Series continues! The second talk will be delivered by Roman Kuznets (TU Wien) next Thursday (March 11th) starting at 12:30. Save the date and join us on Zoom at this link!

Title: Intuiting Duals of Proofs

Abstract: Justification Logic was introduced by Sergei Artemov, under the name of Logic of Proofs, in 1995 as a refinement of modal logic with explicit terms in place of the necessity/provability/knowledge modality. Over the years, multiple modal logics have received a justification treatment, which led to uncovering of the diversity of functional operators hidden within the modality []. For instance, while the K modality can be represented using only two functions on proofs/justifications (concatenation and application), the same modality of strength S5 is realized with two additional operators (positive and negative proof checker). However, the other modal operator <> has never been explored because classically it is simply a dual of []. In this joint work with Sonia Marin and Lutz Straßburger, we explore for the first time the nature of explicit terms for <> in bimodal intuitionistic-style modal logics, such as constructive modal logics, where De Morgan laws do not hold and the modality <> is uncoupled from [].

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New papers in the latest issue of JALs

The Journal of Applied Logic’s latest issue features two new papers by some of our group members. You can easily access them at this link.

M. D’Agostino, C. Larese and S. ModgilTowards Depth-bounded Natural Deduction for Classical First-order Logic

Abstract: In this paper we lay the foundations of a new proof-theory for classical first-order logic that allows for a natural characterization of a notion of inferential depth. The approach we propose here aims towards extending the proof-theoretical framework presented in [6] by combining it with some ideas inspired by Hintikka’s work [18]. Unlike standard natural deduction, in this framework the inference rules that fix the meaning of the logical operators are symmetrical with respect to assent and dissent and do not involve the discharge of formulas. The only discharge rule is a classical dilemma rule whose nested applications provide a sensible measure of inferential depth. The result is a hierarchy of decidable depth-bounded approximations of classical first-order logic that expands the hierarchy of tractable approximations of Boolean logic investigated in [11, 10, 7].

M. Fait and G. PrimieroHTLC: Hyperintensional Typed Lambda Calculus

Abstract: In this paper we introduce the logic HTLC, for Hyperintensional Typed Lambda Calculus. The system extends the typed λ-calculus with hyperintensions and related rules. The polymorphic nature of the system allows to reason with expressions for extensional, intensional and hyperintentsional entities. We inspect meta-theoretical properties and show that HTLC is complete in Henkin’s sense under a weakening of the cardinality constraint for the domain of hyperintensions.

Seminar announcement (F. Riguzzi)

We are all very looking forward to the first seminar of our Logic Lunch seminar series! Next Thursday at 12:30, Fabrizio Riguzzi from the University of Ferrara will discuss Probabilistic Logics. Save the date and join us on Zoom at this link! You can find more information in the abstract and flyer below and don’t forget to follow us on Twitter and Instagram to keep up to date with our news and events!

Title: Probabilistic Logics

Abstract: This talk will present a point of view over the combination of logic and probability theory. I will first discuss two widely adopted logic languages: logic programming and description logics. After the illustration of similarities and differences, I will present how each has been integrated with probability theory using the so called “distribution semantics”. After a discussion of the semantics, I will briefly survey reasoning algorithms.


Passcode: nYfMF9

New Research member!

We are thrilled to have on board Costanza Larese, who has just joined us as a Postdoctoral researcher. Costanza graduated in Philosophy from the University of Pisa and Scuola Normale Superiore, where she also received her Ph.D. with a thesis on the principle of analyticity of logic. She was a visiting student at the Munich Center for Mathematical Philosophy and at the Free University of Berlin. Her research interests include non-classical logics, epistemic and non-monotonic logics, theories of bounded rationality, history and philosophy of logic, history of mathematics. Costanza is funded by the PRIN 2017 project “LOGIC AND COGNITION: Theory, experiments, and applications”. You can visit her website for more information.

A Multi-Agent Depth Bounded Boolean Logic

Recent developments in the formalization of reasoning, especially in computational settings, have aimed at defining cognitive and resource bounds to express limited inferential abilities. This feature is emphasized by Depth Bounded Boolean Logics, an informational logic that models epistemic agents with inferential abilities bounded by the amount of information they can use. However, such logics do not model the ability of agents to make use of information shared by other sources. The present paper provides a first account of a Multi-Agent Depth Bounded Boolean Logic, defining agents whose limited inferential abilities can be increased through a dynamic operation of becoming informed by other data sources.

KEYWORDS: Logic of information, Resource bounded reasoning, Information transmission

Cignarale, G., Primiero, G. A Multi-Agent Depth Bounded Boolean Logic. SEFM 2020. Lecture Notes in Computer Science, vol 12524.