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.

Zoom Link:

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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Applied logic for… the United Nations

I am proud to announce my logical contribution to the “United Nations Convention against Transnational Organized Crime and the Protocols thereto ” (UNTOC), in particular concerning its Review Mechanism.

The Convention represents the only global treaty instrument to fight transnational organized crime, as it counts 190 States parties.

An important obligation for the parties to the Convention is the participation in a peer review mechanism, through which States review each other, on how they implemented the measures requested by the Convention (or its Protocols).

This means that, according to the relevant resolution, each State party should be assigned some reviewers in a random fashion,  subject to  a series of constraints, such as, for instance:

“ (a) States shall not undertake mutual reviews;

(b) For each instrument, a State party under review shall not be reviewed by States which are not parties to the same instrument; in the case that a drawn reviewing State is not party to all the instruments to which the State under review is party, an additional drawing of lots shall be carried out so as to select an additional reviewing State only for those instruments;

(c) The total number of reviewing States for all instruments shall not exceed four unless the State under review decides otherwise…. ”

I was involved at this point, in devising a fair, random procedure for the assignment of reviewers, complying with all the relevant constraints.

After realizing that, due to the intricacies of the requirements, a standard physical procedure, consisting in drawing of lots, would have requested a forbidding amount of time for preparation and material execution, we opted for an automated procedure.

In this task, logic played an essential part. I encoded the legal constraints  into a logical language, and  developed a program, based on the Answer Set Programming paradigm, to find optimal random solutions for the problem at hand.
The program was accepted by the State parties, and is finally to be used on November 23rd, in a plenary meeting with the delegates of all the States for the official assignment of reviewers.


Unfortunately, due to the precautionary measures for the Coronavirus outbreak, we have to cancel yet two seminars in our series: the one scheduled for 12/03, to be held by Pere Pardo (Unimi) and the one scheduled for 19/03, to be held by Anthia Solaki (University of Amsterdam).

We will do our best to have all the canceled seminars rescheduled at a later time this year.