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Logic Seminar

The Logic seminar is held on Wednesdays, usually at 12-14. During the spring 2022 we coninue alternating between online and on campus talks.

The permanent Zoom room for the seminar is: https://helsinki.zoom.us/j/62891400777?pwd=UldCeThTaTJVQjUzUFo4S2ErcndNQT09 (Meeting ID: 628 9140 0777, Passcode: 164195)

PLEASE NOTE: Due to the prevalence of zoom talks given by scholars based in various time zones, the times that the seminar meets will occasionally change from the usual 12-14 slot.

The seminar is led by prof. Juha Kontinen and Juliette Kennedy.



Schedule of the spring term 2022

Wednesday 19.1.2022 12-14, C124

Miika Hannula IN PERSON, with a zoom link (TBA) provided for those following remotely 

Title: "A Dichotomy in Consistent Query Answering for Primary Keys and Unary Foreign Keys", PART 1

Abstract: "In recent years, significant progress has been made in the problem of Consistent Query Answering (CQA) with respect to primary keys. In this problem, the input is a database instance that may violate one or more primary key constraints. A repair is defined as a maximal subinstance that satisfies all primary keys. Given a Boolean query q, the question then is whether q holds true in every repair.



So far, theoretical research in this field has not addressed the combination of primary key and foreign key constraints, despite the importance of referential integrity in database systems. We study CQA with respect to both primary keys and foreign keys, considering the case where foreign keys are unary, and queries are conjunctive queries without self-joins. In this setting, it is natural to adopt the notion of symmetric-difference repairs, since foreign keys can be repaired by adding new tuples. We characterize the boundary between those CQA problems that admit a first-order rewriting, and those that do not. This work is closely connected with dependence logic, since primary and foreign keys correspond respectively to dependence and inclusion atoms.

This is joint work with Jef Wijsen.

Wednesday 26.1.2022 12-14, C124

Miika Hannula IN PERSON, with a zoom link (TBA) provided for those following remotely 

Title: "A Dichotomy in Consistent Query Answering for Primary Keys and Unary Foreign Keys", PART 2

Abstract: "In recent years, significant progress has been made in the problem of Consistent Query Answering (CQA) with respect to primary keys. In this problem, the input is a database instance that may violate one or more primary key constraints. A repair is defined as a maximal subinstance that satisfies all primary keys. Given a Boolean query q, the question then is whether q holds true in every repair.



So far, theoretical research in this field has not addressed the combination of primary key and foreign key constraints, despite the importance of referential integrity in database systems. We study CQA with respect to both primary keys and foreign keys, considering the case where foreign keys are unary, and queries are conjunctive queries without self-joins. In this setting, it is natural to adopt the notion of symmetric-difference repairs, since foreign keys can be repaired by adding new tuples. We characterize the boundary between those CQA problems that admit a first-order rewriting, and those that do not. This work is closely connected with dependence logic, since primary and foreign keys correspond respectively to dependence and inclusion atoms.

This is joint work with Jef Wijsen.

Wednesday 2.2.2022 12-14, C124

The Unsafety of Constancy 

Constancy atoms are among the simplest dependency atoms, and adding them only to First Order Logic yields a language ("Constancy Logic") that is not more expressive than First Order Logic itself. However, adding them to First Order Logic together with other atoms can yield surprising results. In this talk, I will discuss the consequences of adding constancy atoms to logics based on Team Semantics. 

Wednesday 9.2.2022 12-14, C124
Menachem Magidor TBA

Wednesday 16.2.2022 12-14, C124
TBA

Wednesday 23.2.2022 12-14, C124
Gabe Goldberg TBA  IN PERSON

Wednesday 2.3.2022 12-14, C124
TBA

Wednesday 9.3.2022 12-14, C124
Exam week, no seminar

Wednesday 16.3.2022 12-14, C124
TBA

Wednesday 23.3.2022 12-14, C124
TBA

Wednesday 30.3.2022 12-14, C124
TBA

Wednesday 6.4.2022 12-14, C124
TBA

Wednesday 13.4.2022 12-14, C124
TBA

Wednesday 20.4.2022 12-14, C124
Easter break, no seminar

Wednesday 27.4.2022 12-14, C124
TBA

Wednesday 4.5.2022 12-14, C124
TBA

Wednesday 11.5.2022 12-14, C124
Exam week, no seminar



Talks of the fall term 2021

Talks of the spring term 2021

Talks of the fall term 2020

Talks of the spring term 2020

Talks of the fall term 2019

Talks of the spring term 2019

Talks of the fall term 2018

Talks of the spring term 2018

Talks of the fall term 2017

Talks of the spring term 2017

Talks of the fall term 2016

Talks of the spring term 2016

Talks of the fall term 2015

Talks of the spring term 2015

Talks of the fall term 2014

Talks of the spring term 2014

Talks of the fall term 2013

Talks of the spring term 2013

Talks of the fall term 2012

Older talks (2011-2012)

Laboratory of dependence logic

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