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Gabriel Goren-Roig

Publications and source records attributed to Gabriel Goren-Roig.

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Basic Model Theory for Path Predicate Modal Logic

Path Predicate Modal Logic (PPML) is a generalization of Basic Modal Logic, where atoms are relational predicates instead of propositional symbols. The study of PPML is motivated as a way to abstractly investigate data-aware formalisms, such as XPath or DataGL. In this paper, we investigate some basic model theoretical aspects of PPML to better characterize its expressive power. More concretely, we investigate different ways of defining Hennessy-Milner classes, and a van Benthem characterization theorem. In doing so, we discuss the main challenges of dealing with the novel features of PPML, and what are the similarities with the standard approaches.

cs.LO

Presenting Profunctors

Motivated by problems in categorical database theory, we introduce and compare two notions of presentation for profunctors, uncurried and curried, which arise intuitively from thinking of profunctors either as functors C^op x D -> Set or C^op -> Set^D. Although the Cartesian closure of Cat means these two perspectives can be used interchangeably at the semantic level, a surprising amount of subtlety is revealed when looking through the lens of syntax. Indeed, we prove that finite uncurried presentations are strictly more expressive than finite curried presentations, hence the two notions do not induce the same class of finitely presentable profunctors. Moreover, an explicit construction for the composite of two curried presentations shows that the class of finitely curried presentable profunctors is closed under composition, in contrast with the larger class of finitely uncurried presentable profunctors, which is not. This shows that curried profunctor presentations are more appropriate for computational tasks that use profunctor composition. We package our results on curried profunctor presentations into a double equivalence from a syntactic double category into the double category of profunctors. Finally, we study the relationship between curried and uncurried presentations, leading to the introduction of curryable presentations. These constitute a subcategory of uncurried presentations which is equivalent to the category of curried presentations, therefore acting as a bridge between the two syntactic choices.

math.CT

Modal Logic with Relations over Paths: a Theoretical Development through Comonadic Semantics

Game comonads provide categorical semantics for comparison games in Finite Model Theory, thus providing an abstract characterisation of logical equivalence for a wide range of logics, each one captured through a specific choice of comonad. Motivated by the goal of applying comonadic tools to the study of data-aware logics such as CoreDataXPath, in this work we introduce a generalisation of Modal Logic that allows relation symbols of arbitrary arity as atoms of the syntax, which we call Path Predicate Modal Logic or PPML. We motivate this logic as arising from a shift in perspective on a previously studied fragment of CoreDataXPath, called DataGL, and prove that PPML recovers DataGL for a specific choice of signature. We argue that this shift in perspective allows the capturing and designing of new data-aware logics. We introduce resource-bounded simulation and bisimulation games for PPML and show the Hennessy-Milner property relating bisimilarity and logical equivalence. We define the PPML comonad and prove that it captures these games. We develop the model-theoretical understanding of PPML by making systematic use of the comonadic framework. This includes results such as a tree-model property and an alternative proof of the one-way Hennessy-Milner property using a correspondence between positive PPML formulas and canonical models. We also use the comonadic perspective to establish connections with other logics, such as bounded quantifier rank and bounded variable number fragments of First Order Logic on one side and Basic Modal Logic on the other, and show how the PPML comonad induces a syntax-free characterisation of logical equivalence for DataGL, our original motivation. With respect to Basic Modal Logic, a functorial assignment from PPML unravellings into Kripke trees enables us to obtain polynomial-time reductions from PPML problems to their Basic Modal Logic counterparts.

cs.LO