# Raul FervariNational Scientific and Technical Research Council | conicet

Raul Fervari

PhD in Computing Science

## About

43

Publications

3,257

Reads

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362

Citations

Citations since 2016

Introduction

I am currently a researcher at Logics, Interaction and Intelligent Systems group (LIIS) at FaMAF, UNC, Argentina, supported by CONICET. I work in computational aspects of modal logics, in particular my doctoral work was about dynamic logics. My interests include currently:
- the study of proof methods for logics combining operators from modal and separation logics
- the modelling of different kinds of knowledge in epistemic logic
- computational aspects of logics with data comparisons.

Additional affiliations

June 2017 - present

February 2016 - February 2016

**23rd Argentinean Summer School in Informatics RIO 2016**

Position

- Lecturer

Description

- Course: "LogicS: A Modern Perspective" (in spanish)

Education

June 2010 - March 2014

February 2005 - April 2010

## Publications

Publications (43)

Default Logics are a family of non-monotonic formalisms having so-called defaults and extensions as their common foundation. Traditionally, default logics have been defined and dealt with via syntactic notions of consequence in propositional or first-order logic. Here, we build default logics on modal logics. First, we present these default logics...

We approach the concept of Pivotal Rule Consequence (PRC) proposed in [14, 15] from a semantical perspective, resorting to model updates in Public Announcement Logic (PAL) [17]. In doing this, we take inspiration from the notion of dynamic consequence from [3, 6]. Our perspective gains in interest since PRC serves as a “bridge” from Classical Logic...

We study a family of modal logics interpreted on tree-like structures, and featuring local quantifiers ∃^k p that bind the proposition p to worlds that are accessible from the current one in at most k steps. We consider a first-order and a second-order semantics for the quantifiers, which enables us to relate several well-known formalisms, such as...

In this article, we present a modal logic that extends the basic modal logic ML with two dynamic operators: copy (cp), which replicates the current model, labelling each copy with a different propositional symbol and respecting accessibility relations even between distinct copies; and remove (rm), which deletes paths in the model that satisfy certa...

In this paper we introduce sound and strongly complete axiomatizations for
XPath with data constraints extended with hybrid operators. First, we present
HXPath=, a multi-modal version of XPath with data, extended with nominals and
the hybrid operator @. Then, we introduce an axiomatic system for HXPath=, and
we prove it is strongly complete with re...

We introduce a new semantics for a multi-agent epistemic operator of knowing how, based on an indistinguishability relation between plans. Our proposal is, arguably, closer to the standard presentation of knowing that modalities in classical epistemic logic. We study the relationship between this semantics and previous approaches, showing that our...

We introduce a new semantics for a multi-agent epistemic operator of knowing how, based on an indistinguishability relation between plans. Our proposal is, arguably, closer to the standard presentation of knowing that modalities in classical epistemic logic. We study the relationship between this semantics and previous approaches, showing that our...

Modal separation logics are formalisms that combine modal operators to reason locally, with separating connectives that allow to perform global updates on the models. In this work, we design Hilbert-style proof systems for the modal separation logics MSL(∗,〈!=〉) andMSL(∗,〈〉), where ∗ is the separating conjunction,〈〉is the standard modal operator an...

As a new type of epistemic logics, the logics of knowing how capture the high-level epistemic reasoning about the knowledge of various plans to achieve certain goals. Existing work on these logics focuses on axiomatizations; this paper makes the first study of their model theoretical properties. It does so by introducing suitable notions of bisimul...

Over the last years, the study of logics that can update a model while evaluating a formula has gained in interest. Motivated by many examples in practice such as hybrid logics, separation logics and dynamic epistemic logics, the ability to update a model has been investigated from a more general point of view. In this work, we formalize and verify...

Default Logic refers to a family of formalisms designed to carry out non-monotonic reasoning over a monotonic logic (in general, Classical First-Order or Propositional Logic). Traditionally, default logics have been defined and dealt with via syntactic consequence relations. Here, we introduce a family of default logics defined over modal logics. F...

We investigate the expressivity and computational complexity of two modal logics on finite forests equipped with operators to reason on submodels. The logic ML(|) extends the basic modal logic ML with the composition operator | from static ambient logic, whereas ML(*) contains the separating conjunction * from separation logic. Though both operator...

We study the expressivity and complexity of two modal logics interpreted on finite forests and equipped with standard modalities to reason on submodels. The logic ML(C) extends the modal logic K with the composition operator C from ambient logic, whereas ML(∗) features the separating conjunction ∗ from separation logic. Both operators are second-or...

In this paper we introduce sound and strongly complete axiomatizations for XPath with data constraints extended with hybrid operators. First, we present HXPath=, a multi-modal version of XPath with data extended with nominals and the hybrid operator @. Then, we introduce an axiomatic system for HXPath=, and we prove it is strongly complete with res...

Over the last years, the study of logics that can modify a model while evaluating a formula has gained in interest. Motivated by many examples in practice such as hybrid logics, separation logics and dynamic epistemic logics, the ability of updating a model has been investigated from a more general point of view. In this work, we formalize and veri...

We introduce a modal separation logic MSL whose models are memory states from separation logic and the logical connectives include modal operators as well as separating conjunction and implication from separation logic. With such a combination of operators, some fragments of MSL can be seen as genuine modal logics whereas some others capture standa...

We build a Default Logic variant on Intuitionistic Propositional Logic and develop a sound, complete, and terminating, tableaux calculus for it. We also present an implementation of the calculus. We motivate and illustrate the technical elements of our work with examples.

Often, we assume that an action is permitted simply because it is not explicitly forbidden; or, similarly, that an action is forbidden simply because it is not explicitly permitted. This kind of assumptions appear, e.g., in autonomous computing systems where decisions must be taken in the presence of an incomplete set of norms regulating a particul...

Often, we assume that an action is permitted simply because it is not explicitly forbidden; or, similarly, that an action is forbidden simply because it is not explicitly permitted. This kind of assumptions appear, e.g., in autonomous computing systems where decisions must be taken in the presence of an incomplete set of norms regulating a particul...

This work studies positive and negative introspection not as ‘static’ properties an agent might or might not have, but rather as epistemic actions that change the agent’s knowledge. The proposed actions include not only operations for achieving full introspection (first with respect to all formulas, and then with respect to a particular χ), but als...

Modal separation logics are formalisms that combine modal operators to reason locally, with separating connectives that allow to perform global updates on the models. In this work, we design Hilbert-style proof systems for the modal separation logics MSL(*,D) and MSL(*,<>), where * is the separating conjunction, <> is the standard modal operator an...

We investigate interpolation and Beth definability in default logics. To this end, we start by defining a general framework which is sufficiently abstract to encompass most of the usual definitions of a default logic. In this framework a default logic \(\mathscr {D}\mathfrak {L}\) is built on a base, monotonic, logic \(\mathfrak {L}\). We then inve...

Relation-changing modal logics (RC for short) are extensions of the basic modal logic with dynamic operators that modify the accessibility relation of a model during the evaluation of a formula. These languages are equipped with dynamic modalities that are able e.g. to delete, add and swap edges in the model, both locally and globally. We study the...

Relation-changing modal logics are extensions of the basic modal logic that allow to change the accessibility relation of a model during the evaluation of a formula. In particular, they are equipped with dynamic modalities that are able to delete, add and swap edges in the model, both locally and globally. We investigate the satisfiability problem...

This work studies positive and negative introspection not as properties, but rather as actions that change the agent’s knowledge. The actions are introduced as model update operations, with matching modalities expressing their effects. Sound and complete axiom systems are provided, and some properties are explored.

We provide a sound, complete and terminating tableau procedure to check satisfiability of downward XPath\(_=\) formulas enriched with nominals and satisfaction operators. The calculus is inspired by ideas introduced to ensure termination of tableau calculi for certain Hybrid Logics. We prove that even though we increased the expressive power of XPa...

In this paper, we propose a single-agent logic of goal-directed knowing how extending the standard epistemic logic of knowing that with a new knowing how operator. The semantics of the new operator is based on the idea that knowing how to achieve phi means that there exists a (uniform) strategy such that the agent knows that it can make sure phi. W...

We give sound and complete axiomatizations for XPath with data tests by ‘equality’ or ‘inequality’, and containing the single ‘child’ axis. This data-aware logic predicts over data trees, which are tree-like structures whose every node contains a label from a finite alphabet and a data value from an infinite domain. The language allows us to compar...

In this paper, we propose a single-agent logic of goal-directed knowing how extending the standard epistemic logic of knowing that with a new knowing how operator. The semantics of the new operator is based on the idea that knowing how to achieve $\phi$ means that there exists a (uniform) strategy such that the agent knows that it can make sure $\p...

In this paper we introduce a sound and complete axiomatization
for XPath with data constraints extended with hybrid operators.
First, we define HXPath=(↑↓), an extension of vertical XPath with nominals
and the hybrid operator @. Then, we introduce an axiomatic system
for HXPath=(↑↓), and we prove it is complete with respect to the class
of abstract...

Relation-changing modal logics are extensions of the basic modal logic that allow changes to the accessibility relation of a model during the evaluation of a formula. In particular, they are equipped with dynamic modalities that are able to delete, add, and swap edges in the model, both locally and globally. We provide translations from these logic...

We give sound and complete axiomatizations for XPath with data tests by "equality" or "inequality", and containing the single "child" axis. This data-aware logic predicts over data trees, which are tree-like structures whose every node contains a label from a finite alphabet and a data value from an infinite domain. The language allows us to compar...

We study dynamic modal operators that can change the accessibility relation of a model during the evaluation of a formula.
In particular, we extend the basic modal language with modalities that are able to delete, add or swap an edge between pairs
of elements of the domain. We define a generic framework to characterize this kind of operations. Firs...

We propose a logic with the dynamic modal operators copy and remove. The copy operator replicates a given model, and the remove operator removes paths in a given model. We show that the product update by an action model in dynamic epistemic logic decomposes in copy and remove operations, when we consider action models with Boolean preconditions and...

We propose a logic with the dynamic modal operators copy and remove. The copy operator replicates a given model, and the remove operator removes paths in a given model. We show that the product update by an action model (with Boolean pre-conditions) in dynamic epistemic logic decomposes in copy and remove operations. We also show that copy and remo...

We propose a logic with the dynamic modal operators copy and remove. The copy operator replicates a given model, and the remove operator removes paths in a given model. We show that the product update by an action model (with Boolean pre-conditions) in dynamic epistemic logic decomposes in copy and remove operations. We also show that copy and remo...

We investigate dynamic modal operators that can change the model during evaluation. We define the logic S S L L by extending the basic modal language with the modality, which is a diamond operator that in addition has the ability to invert pairs of related elements in the domain
while traversing an edge of the accessibility relation. S S L L is ver...

In this thesis we study dynamic modal operators that can change the model during
the evaluation of a formula. In particular, we extend the basic modal language
with modalities that are able to swap, delete or add pairs of related elements of
the domain. We call the resulting logics Relation-Changing Modal Logics. We study
local version of the opera...

We consider dynamic modal operators that can change the relation of a model during the evaluation of a formula. In this paper, we extend the basic modal language with modalities that are able to delete, add or swap pairs of related elements of the domain; and explore tableau calculi as satisfiability procedures for these logics.

In this paper we discuss ideas about dynamic modal logics. Modal logics are appropriate to describe properties of relational structures, and several operators have been already introduced to describe dynamic properties of such structures. However, we are interested in those operators which can modify models during the evaluation of a formula. First...

Modal logics are appropriate to describe properties of graphs. But usually these are static properties. We investigate dynamic modal operators that can change the model during evaluation. We define the logic SL by extending the basic modal language with the ♦ modality, which is a diamond operator that has the ability to invert pairs of related elem...

We study dynamic modal operators that can change the model during the evaluation of a formula. In particular, we extend the basic modal language with modalities that are able to swap, delete or add pairs of related elements of the domain, while traversing an edge of the accessibility relation. We study these languages together with the sabotage mod...

DynAlloy is an extension to the Alloy specification language suitable for modeling properties of executions of software systems. Dy-nAlloy provides fully automated support for verifying properties of pro-grams, in the style of the Alloy Analyzer, i.e., by exhaustively searching for counterexamples of properties in bounded scenarios (bounded do-main...

## Projects

Projects (4)

Separation logic has been introduced as an extension of Hoare-Floyd logic to verify programs with mutable data structures. A major feature is to be able to reason locally in a modular way, which can be performed thanks to the separating conjunction (∗) that allows one to state properties in disjoint parts of the memory.
In this project, we wish to present new results about decidability, complexity and expressive power of various problems connected with this logic.