Papers by Silvano Colombo Tosatto
arXiv (Cornell University), Sep 9, 2022
This paper presents an extension of Defeasible Deontic Logic to deal with the Pragmatic Oddity pr... more This paper presents an extension of Defeasible Deontic Logic to deal with the Pragmatic Oddity problem. The logic applies three general principles: (1) the Pragmatic Oddity problem must be solved within a general logical treatment of CTD reasoning; (2) non-monotonic methods must be adopted to handle CTD reasoning; (3) logical models of CTD reasoning must be computationally feasible and, if possible, efficient. The proposed extension of Defeasible Deontic Logic elaborates a preliminary version of the model proposed by Governatori and Rotolo [15]. The previous solution was based on particular characteristics of the (constructive, top-down) proof theory of the logic. However, that method introduces some degree of non-determinism. To avoid the problem, we provide a bottom-up characterisation of the logic. The new characterisation offers insights for the efficient implementation of the logic and allows us to establish the computational complexity of the problem.
Dealing with Unexpected Runtime Outcomes Within Process Models
Springer eBooks, 2022
Lecture Notes in Business Information Processing
Prescriptive process monitoring approaches leverage historical data to prescribe runtime interven... more Prescriptive process monitoring approaches leverage historical data to prescribe runtime interventions that will likely prevent negative case outcomes or improve a process’s performance. A centerpiece of a prescriptive process monitoring method is its intervention policy: a decision function determining if and when to trigger an intervention on an ongoing case. Previous proposals in this field rely on intervention policies that consider only the current state of a given case. These approaches do not consider the tradeoff between triggering an intervention in the current state, given the level of uncertainty of the underlying predictive models, versus delaying the intervention to a later state. Moreover, they assume that a resource is always available to perform an intervention (infinite capacity). This paper addresses these gaps by introducing a prescriptive process monitoring method that filters and ranks ongoing cases based on prediction scores, prediction uncertainty, and causal ...
arXiv (Cornell University), May 12, 2021
Organisations are required to show that their procedures and processes satisfy the relevant regul... more Organisations are required to show that their procedures and processes satisfy the relevant regulatory requirements. The computational complexity of proving regulatory compliance is known to be generally hard. However, for some of its simpler variants the computational complexity is still unknown. We focus on the eight variants of the problem that can be identified by the following binary properties: whether the requirements consists of one or multiple obligations, whether the obligations are conditional or always in force, and whether only propositional literals or formulae can be used to describe the obligations. This paper in particular shows that proving full compliance of a model against a single unconditional obligation whose elements can be described using formulae is coNP-complete. Finally we show how this result allows to fully map the computational complexity of these variants for proving full and non compliance, while for partial compliance the complexity result of one of the variants is still missing.
Journal of Logic and Computation
This paper presents an extension of Defeasible Deontic Logic to deal with the Pragmatic Oddity pr... more This paper presents an extension of Defeasible Deontic Logic to deal with the Pragmatic Oddity problem. The logic applies three general principles: (i) the Pragmatic Oddity problem must be solved within a general logical treatment of contrary-to-duty (CTD) reasoning; (ii) non-monotonic methods must be adopted to handle CTD reasoning; (iii) logical models of CTD reasoning must be computationally feasible and, if possible, efficient. The proposed extension of Defeasible Deontic Logic elaborates a preliminary version of the model proposed by Governatori and Rotolo [15]. The previous solution was based on particular characteristics of the (constructive, top-down) proof theory of the logic. However, that method introduces some degree of non-determinism. To avoid the problem, we provide a bottom-up characterization of the logic. The new characterization offers insights for the efficient implementation of the logic and allows us to establish the computational complexity of the problem.
In the present chapter we focus our attention on the computational complexity of proving regulato... more In the present chapter we focus our attention on the computational complexity of proving regulatory compliance of business process models. While the topic has never received the deserved attention, we argue that the theoretical results, both existing and yet to find, are far reaching for many areas related to the problem of proving compliance of process models. Therefore, we provide here and discuss the existing results concerning the theoretical computational complexity of the problem, as well as discussing some further areas that can potentially advance the knowledge about the issue, and other closely related disciplines that can either bring or take insights to this area.
Social Science Research Network, Mar 18, 2020
We introduce a variant of Deontic Defeasible Logic to handle the issue of Pragmatic Oddity. The k... more We introduce a variant of Deontic Defeasible Logic to handle the issue of Pragmatic Oddity. The key idea is that a conjunctive obligation is allowed only when each individual obligation is independent from the violation of the other obligations. The solution makes essential use of the constructive proof theory of the logic while maintaining a feasible computational complexity.
Execution of business processes often requires resources, the use of which is usually subject to ... more Execution of business processes often requires resources, the use of which is usually subject to constraints. In this paper, we study the compliance of business processes with resource usage policies. To this end, we relate the execution of a business process to its resource requirements in terms of resources consumed, produced or blocked by tasks of the business process. Policies specifying constraints on resource usage are specified in the form of obligations and the verification of whether a business process complies with a given resource usage policy is formally studied.
Abstract. The aim of the paper is to bring to the realm of game theory the well-known deontic not... more Abstract. The aim of the paper is to bring to the realm of game theory the well-known deontic notion of contrary-to-duty (CTD) obligation, so far not investigated in relation to optimality of strategic decisions. We maintain that, under a game-theoretical semantics, CTDs are well-suited to treat sub-ideal decisions. We also argue that, in a wide class of interactions, CTDs can used as a compact representation of coalitional choices leading to the achievement of optimal outcomes. Finally we investigate the properties of the proposed operators.
The majority of work in judgment aggregation is devoted to the study of impossibility results. Ho... more The majority of work in judgment aggregation is devoted to the study of impossibility results. However the (social) dependencies that may exist between the voters has received less attention. In this extended abstract we use the degree centrality measure from social network analysis and obtain a correspondence between the average voter rule and this measure, and show that approach can lead to more resolute outcomes in the voting process.
Proving Regulatory Compliance: Business Processes, Logic, Complexity
The majority of work in judgment aggregation is devoted to the study of impossibility results. Ho... more The majority of work in judgment aggregation is devoted to the study of impossibility results. However the (social) dependencies that may exist between the voters has received less attention. In this extended abstract we use the degree centrality measure from social network analysis and obtain a correspondence between the average voter rule and this measure, and show that approach can lead to more resolute outcomes in the voting process.
Automatic Extraction of Legal Norms: Evaluation of Natural Language Processing Tools
In the present extended abstract we describe the simulator developed. The purpose of this simulat... more In the present extended abstract we describe the simulator developed. The purpose of this simulator is to test our neural symbolic approach towards normative reasoning. After the translation process provided by the simulator I describe one of the case study used during the experiments. To be more precise, the case study regards RoboCup scenario.
In this paper we provide a neural-symbolic framework to model, reason about and learn norms in mu... more In this paper we provide a neural-symbolic framework to model, reason about and learn norms in multi-agent systems. To this purpose, we define a fragment of Input/Output (I/O) logic that can be embedded into a neural network. We extend d'Avila Garcez et al. Connectionist Inductive Learning and Logic Programming System (CILP) to translate an I/O logic theory into a Neural Network (NN) that can be trained further with examples: we call this new system Normative-CILP (N-CILP). We then present a new algorithm to handle priorities between rules in order to cope with normative issues like Contrary to Duty (CTD), Priorities, Exceptions and Permissions. We illustrate the applicability of the framework on a case study based on RoboCup rules: within this working example, we compare the learning capacity of a network built with N-CILP with a non symbolic neural network, we explore how the initial knowledge impacts on the overall performance, and we test the NN capacity of learning norms, g...
Normative systems are dynamic systems because their rules can change over time. Considering this ... more Normative systems are dynamic systems because their rules can change over time. Considering this problem, we propose a neuralsymbolic approach to provide agents the instruments to reason about and learn norms in a dynamic environment. We propose a variant of d’Avila Garcez et al. Connectionist Inductive Learning and Logic Programming(CILP) System to embed Input/Output logic normative rules into a feed-forward neural network. The resulting system called Normative-CILP(NCILP) shows how neural networks can cope with some of the underpinnings of normative reasoning: permissions, dilemmas, exceptions and contrary to duty problems. We have applied our approach in a simplified RoboCup environment, using the N-CILP simulator that we have developed. In the concluding part of the paper, we provide some of the results obtained in the experiments.
Linear Logic and Defeasible Logic have been adopted to formalise different features relevant to a... more Linear Logic and Defeasible Logic have been adopted to formalise different features relevant to agents: consumption of resources, and reasoning with exceptions. We propose a framework to combine sub-structural features, corresponding to the consumption of resources, with defeasibility aspects, and we discuss the design choices for the framework.
Principles and Semantics: Modelling Violations for Normative Reasoning
AI Approaches to the Complexity of Legal Systems XI-XII
In this paper, we present a new methodology to evaluate whether a business process model is fully... more In this paper, we present a new methodology to evaluate whether a business process model is fully compliant with a regulatory framework composed of a set of conditional obligations. The methodology is based failure delta-constraints that are evaluated on bottom-up aggregations of a tree-like representation of business process models. While the generic problem of proving full compliance is in coNP-complete, we show that verifying full compliance can be done in polynomial time using our methodology, for an acyclic structured process model given a regulatory framework composed by a set of conditional obligations, whose elements are restricted to be represented by propositional literals
ArXiv, 2021
Organisations model their processes using so-called business process models, to allow for verific... more Organisations model their processes using so-called business process models, to allow for verification of their correctness with respect to regulatory requirements and business rules. Automated methods for checking compliance, however, have to deal with the high complexity of the requirements as well as the significant size and quantity of process models in an organisation, which may prevent process models from being checked efficiently and timely. This paper provides a computational complexity analysis of the problem of proving regulatory compliance of process models. We investigate the computational complexity of each variant of the problem resulting from a combination of three binary properties associated to the regulatory framework, determining the regulatory requirements that a process model needs to follow to be compliant. These binary properties are whether the framework contains one or multiple obligations, whether the obligations are global or conditional, and whether only ...
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Papers by Silvano Colombo Tosatto