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Giorgio Cignarale

Publications and source records attributed to Giorgio Cignarale.

7 recordsLinked to original sources

From Actions to Obligations: A Deontic Action Model Logic

We introduce the Deontic Action Model Logic (DAML), a dynamic modal framework for reasoning about obligations over actions in multi-agent systems. DAML extends the epistemic Action Model Logic by incorporating deontic evaluation mechanisms that assess agents' actions in terms of both the desirability and the likelihood of their outcomes. Obligations arise for those actions that maximize expected deontic value among an agent's available alternatives at a given decision point, yielding a formal account for reasoning about conditional and context-sensitive obligations in settings involving strategic interaction and incomplete information. DAML supports principled action selection in norm-governed multi-agent systems, and is the first such framework to derive these obligations using the action model logic machinery. We provide an axiomatization of the logic and prove soundness and completeness with respect to its semantics. Finally, we demonstrate the expressive power of our framework through applications to the Miners' Puzzle and other multi-agent deontic scenarios.

cs.LO

A Dynamic Deontic Simplicial Logic for Joint Commitments

We introduce the Deontic Simplicial Logic (DSL), a deontic logic for group obligations grounded in simplicial complexes: vertices encode individual commitments, and higher-dimensional simplices encode the joint commitments of the groups they connect. The resulting group modality behaves like a distributed-commitment operator with a genuinely normative character: it validates achievement but not the unrestricted introspection or monotonicity familiar from its epistemic counterpart, and impurity lets the model distinguish an agent's mere absence from a configuration from an explicit commitment to the contrary. We give a sound and complete axiomatization for the group modality. We then extend DSL to the Dynamic Deontic Simplicial Logic (DDSL), which introduces action modalities modeling agents' choices among mutually exclusive commitments, with effects captured by a product update construction on simplicial models; to our knowledge, this is the first dynamic deontic logic built on simplicial complexes. Soundness and completeness for DDSL are established via reduction axioms to the static case. Throughout, we illustrate both logics with worked examples of static and dynamic multi-agent commitment scenarios.

cs.LO

Self-Correcting Gossip Protocols

We investigate self-correcting gossip protocols with errors. In distributed computing, protocols with errors have been widely investigated in temporal epistemic logics. Instead, we propose a dynamic epistemic logic. We show how to correct transmission errors due to faulty messages without a central authority coordinating protocol execution, how this affects optimality, and how this compares to bounded memory and full information protocols.

cs.LO

Knowledge in multi-robot systems: an interplay of dynamics, computation and communication

In this paper, we provide a framework integrating distributed multi-robot systems and temporal epistemic logic. We show that continuous-discrete hybrid systems are compatible with logical models of knowledge already used in distributed computing, and demonstrate its usefulness by deriving sufficient epistemic conditions for exploration and gathering robot tasks to be solvable. We provide a separation of the physical and computational aspects of a robotic system, allowing us to decouple the problems related to each and directly use methods from control theory and distributed computing, fields that are traditionally distant in the literature. Finally, we demonstrate a novel approach for reasoning about the knowledge in multi-robot systems through a principled method of converting a switched hybrid dynamical system into a temporal-epistemic logic model, passing through an abstract state machine representation. This creates space for methods and results to be exchanged across the fields of control theory, distributed computing and temporal-epistemic logic, while reasoning about multi-robot systems.

cs.LO

Consistent Update Synthesis via Privatized Beliefs

Kripke models are an effective and widely used tool for representing epistemic attitudes of agents in multi-agent systems, including distributed systems. Dynamic Epistemic Logic (DEL) adds communication in the form of model transforming updates. Private communication is key in distributed systems as processes exchanging (potentially corrupted) information about their private local state should not be detectable by any other processes. This focus on privacy clashes with the standard DEL assumption for which updates are applied to the whole Kripke model, which is usually commonly known by all agents, potentially leading to information leakage. In addition, a commonly known model cannot minimize the corruption of agents' local states due to fault information dissemination. The contribution of this paper is twofold: (I) To represent leak-free agent-to-agent communication, we introduce a way to synthesize an action model which stratifies a pointed Kripke model into private agent-clusters, each representing the local knowledge of the processes: Given a goal formula $φ$ representing the effect of private communication, we provide a procedure to construct an action model that (a) makes the goal formula true, (b) maintain consistency of agents' beliefs, if possible, without causing "unrelated" beliefs (minimal change) thus minimizing the corruption of local states in case of inconsistent information. (II) We introduce a new operation between pointed Kripke models and pointed action models called pointed updates which, unlike the product update operation of DEL, maintain only the subset of the world-event pairs that are reachable from the point, without unnecessarily blowing up the model size.

cs.LO

A Sufficient Epistemic Condition for Solving Stabilizing Agreement

In this paper we provide a first-ever epistemic formulation of stabilizing agreement, defined as the non-terminating variant of the well established consensus problem. In stabilizing agreements, agents are given (possibly different) initial values, with the goal to eventually always decide on the same value. While agents are allowed to change their decisions finitely often, they are required to agree on the same value eventually. We capture these properties in temporal epistemic logic and we use the Runs and Systems framework to formally reason about stabilizing agreement problems. We then epistemically formalize the conditions for solving stabilizing agreement, and identify the knowledge that the agents acquire during any execution to choose a particular value under our system assumptions. This first formalization of a sufficient condition for solving stabilizing agreement sets the stage for a planned necessary and sufficient epistemic characterization of stabilizing agreement.

cs.DC

A priori Belief Updates as a Method for Agent Self-Recovery

Standard epistemic logic is concerned with describing agents' epistemic attitudes given the current set of alternatives the agents consider possible. While distributed systems can (and often are) discussed without mentioning epistemics, it has been well established that epistemic phenomena lie at the heart of what agents, or processes, can and cannot do. Dynamic epistemic logic (DEL) aims to describe how epistemic attitudes of the agents/processes change based on the new information they receive, e.g., based on their observations of events and actions in a distributed system. In a broader philosophical view, this appeals to an a posteriori kind of reasoning, where agents update the set of alternatives considered possible based on their "experiences." Until recently, there was little incentive to formalize a priori reasoning, which plays a role in designing and maintaining distributed systems, e.g., in determining which states must be considered possible by agents in order to solve the distributed task at hand, and consequently in updating these states when unforeseen situations arise during runtime. With systems becoming more and more complex and large, the task of fixing design errors "on the fly" is shifted to individual agents, such as in the increasingly popular self-adaptive and self-organizing (SASO) systems. Rather than updating agents' a posteriori beliefs, this requires modifying their a priori beliefs about the system's global design and parameters. The goal of this paper is to provide a formalization of such a priori reasoning by using standard epistemic semantic tools, including Kripke models and DEL-style updates, and provide heuristics that would pave the way to streamlining this inherently non-deterministic and ad hoc process for SASO systems.

cs.DC