Francesco Dagnino

Francesco Dagnino
Università degli Studi di Genova | UNIGE · Dipartimento di Informatica, Bioingegneria, Robotica e Ingegneria dei Sistemi (DIBRIS)

PhD in Computer Science

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31
Publications
1,177
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72
Citations

Publications

Publications (31)
Preprint
Full-text available
In type-and-coeffect systems, contexts are enriched by coeffects modeling how they are actually used, typically through annotations on single variables. Coeffects are computed bottom-up, combining, for each term, the coeffects of its subterms, through a fixed set of algebraic operators. We show that this principled approach can be adopted to track...
Article
It is well known that big-step semantics is not able to distinguish stuck and non-terminating computations. This is a strong limitation as it makes it very difficult to reason about properties involving infinite computations, such as type soundness, which cannot even be expressed. We show that this issue is only apparent: the distinction between st...
Preprint
Full-text available
There exists a broad family of multiparty sessions in which the progress of one session participant is not unconditional, but depends on the choices performed by other participants. These sessions fall outside the scope of currently available session type systems that guarantee progress. In this work we propose the first type system ensuring that w...
Preprint
Full-text available
Multiparty sessions with asynchronous communications and global types play an important role for the modelling of interaction protocols in distributed systems. In designing such calculi the aim is to enforce, by typing, good properties for all participants, maximising, at the same time, the behaviours accepted. The global types presented in this pa...
Preprint
Full-text available
Quantitative reasoning provides a flexible approach capable to deal with the uncertainty and imprecision that affects modern software systems due to their complexity. Its distinguishing feature is the use of distances, instead of equivalence relations, so that one can measure how much two objects are similar, rather than just saying whether they ar...
Article
Inference systems are a widespread framework used to define possibly recursive predicates by means of inference rules. They allow both inductive and coinductive interpretations that are fairly well-studied. In this paper, we consider a middle way interpretation, called regular, which combines advantages of both approaches: it allows non-well-founde...
Article
Full-text available
Doctrines are categorical structures very apt to study logics of different nature within a unified environment: the 2-category Dtn of doctrines. Modal interior operators are characterised as particular adjoints in the 2-category Dtn . We show that they can be constructed from comonads in Dtn as well as from adjunctions in it, and we compare the two...
Preprint
Full-text available
Doctrines are categorical structures very apt to study logics of different nature within a unified environment: the 2-category Dtn of doctrines. Modal interior operators are characterised as particular adjoints in the 2-category Dtn. We show that they can be constructed from comonads in Dtn as well as from adjunctions in it, and the two constructio...
Chapter
Global types are at the core of communication based programming. They allow a high level specification of protocols involving many participants and enforce good safety and liveness properties, such as absence of deadlock, locked participants and orphan messages. In this paper, we describe an implementation of a novel formalism of global types for s...
Chapter
Multiparty sessions with asynchronous communications and global types play an important role for the modelling of interaction protocols in distributed systems. In designing such calculi the aim is to enforce, by typing, good properties for all participants, maximising, at the same time, the behaviours accepted. The global types presented in this pa...
Preprint
Full-text available
It is well-known that big-step semantics is not able to distinguish stuck and non-terminating computations. This is a strong limitation as it makes very difficult to reason about properties involving infinite computations, such as type soundness, which cannot even be expressed. To face this problem, we develop a systematic study of big-step semanti...
Article
Recursive definitions of predicates are usually interpreted either inductively or coinductively. Recently, a more powerful approach has been proposed, called flexible coinduction , to express a variety of intermediate interpretations, necessary in some cases to get the correct meaning. We provide a detailed formal account of an extension of logic p...
Preprint
Recursive definitions of predicates are usually interpreted either inductively or coinductively. Recently, a more powerful approach has been proposed, called flexible coinduction, to express a variety of intermediate interpretations, necessary in some cases to get the correct meaning. We provide a detailed formal account of an extension of logic pr...
Preprint
Full-text available
Inference systems are a widespread framework used to define possibly recursive predicates by means of inference rules. They allow both inductive and coinductive interpretations that are fairly well-studied. In this paper, we consider a middle way interpretation, called regular, which combines advantages of both approaches: it allows non-well-founde...
Article
We provide a construction that, given a big-step semantics describing finite computations and their observations, extends it to include infinite computations as well. The basic idea is that the finite behaviour uniquely determines the infinite behaviour once observations and their composition operators are fixed. Technically, the construction relie...
Preprint
Full-text available
The aim of the paper is to provide solid foundations for a programming paradigm natively supporting the creation and manipulation of cyclic data structures. To this end, we describe coFJ, a Java-like calculus where objects can be infinite and methods are equipped with a codefinition (an alternative body). We provide an abstract semantics of the cal...
Chapter
We propose a general proof technique to show that a predicate is sound, that is, prevents stuck computation, with respect to a big-step semantics. This result may look surprising, since in big-step semantics there is no difference between non-terminating and stuck computations, hence soundness cannot even be expressed. The key idea is to define con...
Preprint
Full-text available
We propose a general proof technique to show that a predicate is sound, that is, prevents stuck computation, with respect to a big-step semantics. This result may look surprising, since in big-step semantics there is no difference between non-terminating and stuck computations, hence soundness cannot even be expressed. The key idea is to define con...
Preprint
Theorem provers are tools that help users to write machine readable proofs. Some of this tools are also interactive. The need of such softwares is increasing since they provide proofs that are more certified than the hand written ones. Agda is based on type theory and on the propositions-as-types correspondence and has a Haskell-like syntax. This m...
Conference Paper
The semantics of programming languages or software systems generally specifies, for each program/system configuration, its final result, if any. In literature, there are two main approaches to define such a relation in an operational way: either on top of a small-step relation [12, 13], representing single computation step, or directly by a set of...
Preprint
Full-text available
We introduce a generalized notion of inference system to support more flexible interpretations of recursive definitions. Besides axioms and inference rules with the usual meaning, we allow also coaxioms, which are, intuitively, axioms which can only be applied "at infinite depth" in a proof tree. Coaxioms allows us to interpret recursive definition...
Conference Paper
The standard Java API defines a number of useful and widely used interfaces, where the flow of methods invoked on objects must follow certain patterns to ensure their correct use. Typically, such patterns are informally specified in the documentation with several rules, which often do not cover full details, and are scattered throughout the whole d...
Conference Paper
Generalized inference systems have been recently introduced, and used, among other applications, to define semantic judgments which uniformly model terminating computations and divergence. We show that the approach can be successfully extended to more sophisticated notions of infinite behaviour, that is, to express that a diverging computation prod...
Thesis
After surveying classical results, we introduce a generalized notion of inference system to support structural recursion on non-well-founded data types. Besides axioms and inference rules with the usual meaning, a generalized inference system allows coaxioms, which are, intuitively, axioms which can only be applied "at infinite depth" in a proof tr...
Article
Coaxioms have been recently introduced to enhance the expressive power of inference systems, by supporting interpretations which are neither purely inductive, nor coinductive. This paper proposes a novel approach based on coaxioms to capture divergence in semantic definitions by allowing inductive and coinductive semantic rules to be merged togethe...
Article
Full-text available
We introduce a generalized logic programming paradigm where programs, consisting of facts and rules with the usual syntax, can be enriched by co-facts, which syntactically resemble facts but have a special meaning. As in coinductive logic programming, interpretations are subsets of the complete Herbrand basis, including infinite terms. However, the...
Conference Paper
We introduce a generalized notion of inference system to support structural recursion on non well-founded datatypes. Besides axioms and inference rules with the usual meaning, a generalized inference system allows coaxioms, which are, intuitively, axioms which can only be applied “at infinite depth” in a proof tree. This notion nicely subsumes stan...
Conference Paper
We face the problem of providing a denotational semantics for corecursive methods with default, a programming feature for manipulating cyclic structures without ad-hoc machinery. To this aim, we study new lattices for which the theorem of Kleene is applicable so that the semantics of a corecursive method with default corresponds to the greatest fix...

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