Computational Aspects of Dependence Logic

In this thesis (modal) dependence logic is investigated. It was introduced in 2007 by Jouko V\"a\"aan\"anen as an extension of first-order (resp. modal) logic by the dependence operator =(). For first-order (resp. propositional) variables x_1,...,x_n, =(x_1,...,x_n) intuitively states that the value of x_n is determined by those of x_1,...,x_n-1. We consider fragments of modal dependence logic obtained by restricting the set of allowed modal and propositional connectives. We classify these fragments with respect to the complexity of their satisfiability and model-checking problems. For satisfiability we obtain complexity degrees from P over NP, Sigma_P^2 and PSPACE up to NEXP, while for model-checking we only classify the fragments with respect to their tractability, i.e. we either show NP-completeness or containment in P. We then study the extension of modal dependence logic by intuitionistic implication. For this extension we again classify the complexity of the model-checking problem for its fragments. Here we obtain complexity degrees from P over NP and coNP up to PSPACE. Finally, we analyze first-order dependence logic, independence-friendly logic and their two-variable fragments. We prove that satisfiability for two-variable dependence logic is NEXP-complete, whereas for two-variable independence-friendly logic it is undecidable; and use this to prove that the latter is also more expressive than the former.Comment: PhD thesis; 138 pages (110 main matter

The Expressive Power of Modal Dependence Logic

We study the expressive power of various modal logics with team semantics. We show that exactly the properties of teams that are downward closed and closed under team k-bisimulation, for some finite k, are definable in modal logic extended with intuitionistic disjunction. Furthermore, we show that the expressive power of modal logic with intuitionistic disjunction and extended modal dependence logic coincide. Finally we establish that any translation from extended modal dependence logic into modal logic with intuitionistic disjunction increases the size of some formulas exponentially.Comment: 19 page

Complexity of validity for propositional dependence logics

We study the validity problem for propositional dependence logic, modal dependence logic and extended modal dependence logic. We show that the validity problem for propositional dependence logic is NEXPTIME-complete. In addition, we establish that the corresponding problem for modal dependence logic and extended modal dependence logic is NEXPTIME-hard and in NEXPTIME^NP.Comment: In Proceedings GandALF 2014, arXiv:1408.556

On Extensions and Variants of Dependence Logic : A study of intuitionistic connectives in the team semantics setting

Dependence logic is a new logic which incorporates the notion of dependence , as well as independence between variables into first-order logic. In this thesis, we study extensions and variants of dependence logic on the first-order, propositional and modal level. In particular, the role of intuitionistic connectives in this setting is emphasized. We obtain, among others, the following results: 1. First-order intuitionistic dependence logic is proved to have the same expressive power as the full second-order logic. 2. Complete axiomatizations for propositional dependence logic and its variants are obtained. 3. The complexity of model checking problem for modal intuitionistic dependence logic is analyzed.Riippuvuus ja riippumattomuus ovat yleisiä ilmiöitä monella alalla aina tietojenksittelytieteestä (tietokannat, ohjelmistotekniikka, tiedon esitys, tekoäly) valtiotieteisiin (historia, osakemarkkinat). 1960-luvulta lähtien matemaatikot ja filosofit ovat olleet tietoisia klassisen ensimmäisen kertaluvun logiikan rajoitteista muuttujien riippuvuuden ja riippumattomuuden ilmaisemisessa. Ongelman ratkaisemiseksi Henkin (1961) laajensi ensimmäisen kertaluvun logiikkaa haarautuvilla kvanttoreilla ja Hintikka ja Sandu (1989) määrittelivät IF-logiikan. Väänäsen (2007) kehittämä riippuvuuslogiikka on uusi suunta lähestymistavoissa. Riippuvuuslogiikan käsitteellinen uutuus on lisätä vaatimukset riippuvuudesta ja riippumattomuudesta atomaariselle tasolle, eikä kvanttoritasolle, kuten aiemmissa lähestymistavoissa. Lisäksi logiikan metodologia on täysin uusi: tavanomaisesta yhteen tulkintafunktioon perustuvasta Tarksin semantiikasta poiketen riippuvuuslogiikan toteutuvuusrelaatio määrtellään tulkintafunktiojoukon suhteen (alunperin Hodgesilta, 1997). Riippuvuuslogiikka on luonteeltaan hyvin monitieteinen ja siksi logiikalla, ja sen monilla laajennuksilla ja muunnelmilla, on mahdollisia sovelluksia mm. tietokantateorian, kielifilosofian ja valtiotieteiden aloilla. Tämä väitöskirja tutkii riippuvuuslogiikan laajennuksia ja muunnelmia. Erityisesti painotetaan intuitionististen konnektiivien roolia tässä lähestymistavassa. Päätuloksia ovat: 1. Ensimmäisen kertaluvun intuitionistisen riippuvuuslogiikan ilmaisuvoima osoitetaan yhtä vahvaksi kuin täyden toisen kertaluvun logiikan. 2. Annetaan täydellisiä aksiomatisointeja propositionaaliselle riippuvuuslogiikalle ja sen variaatioille. 3. Analysodaan modaalisen intuitionsitisen riippuvuuslogiikan mallintarkastusongelman kompleksisuutta

Tool support for reasoning in display calculi

We present a tool for reasoning in and about propositional sequent calculi. One aim is to support reasoning in calculi that contain a hundred rules or more, so that even relatively small pen and paper derivations become tedious and error prone. As an example, we implement the display calculus D.EAK of dynamic epistemic logic. Second, we provide embeddings of the calculus in the theorem prover Isabelle for formalising proofs about D.EAK. As a case study we show that the solution of the muddy children puzzle is derivable for any number of muddy children. Third, there is a set of meta-tools, that allows us to adapt the tool for a wide variety of user defined calculi

The expressive power of modal logic with inclusion atoms

Modal inclusion logic is the extension of basic modal logic with inclusion atoms, and its semantics is defined on Kripke models with teams. A team of a Kripke model is just a subset of its domain. In this paper we give a complete characterisation for the expressive power of modal inclusion logic: a class of Kripke models with teams is definable in modal inclusion logic if and only if it is closed under k-bisimulation for some integer k, it is closed under unions, and it has the empty team property. We also prove that the same expressive power can be obtained by adding a single unary nonemptiness operator to modal logic. Furthermore, we establish an exponential lower bound for the size of the translation from modal inclusion logic to modal logic with the nonemptiness operator.Comment: In Proceedings GandALF 2015, arXiv:1509.0685

Axiomatizing propositional dependence logics

We give sound and complete Hilbert-style axiomatizations for propositional dependence logic (PD), modal dependence logic (MDL), and extended modal dependence logic (EMDL) by extending existing axiomatizations for propositional logic and modal logic. In addition, we give novel labeled tableau calculi for PD, MDL, and EMDL. We prove soundness, completeness and termination for each of the labeled calculi