Computing Strong and Weak Permissions in Defeasible Logic

In this paper we propose an extension of Defeasible Logic to represent and compute three concepts of defeasible permission. In particular, we discuss different types of explicit permissive norms that work as exceptions to opposite obligations. Moreover, we show how strong permissions can be represented both with, and without introducing a new consequence relation for inferring conclusions from explicit permissive norms. Finally, we illustrate how a preference operator applicable to contrary-to-duty obligations can be combined with a new operator representing ordered sequences of strong permissions which derogate from prohibitions. The logical system is studied from a computational standpoint and is shown to have liner computational complexity

Thou Shalt is not You Will

In this paper we discuss some reasons why temporal logic might not be suitable to model real life norms. To show this, we present a novel deontic logic contrary-to-duty/derived permission paradox based on the interaction of obligations, permissions and contrary-to-duty obligations. The paradox is inspired by real life norms

Conformance Verification of Normative Specifications using C-O Diagrams

C-O Diagrams have been introduced as a means to have a visual representation of normative texts and electronic contracts, where it is possible to represent the obligations, permissions and prohibitions of the different signatories, as well as what are the penalties in case of not fulfillment of their obligations and prohibitions. In such diagrams we are also able to represent absolute and relative timing constrains. In this paper we consider a formal semantics for C-O Diagrams based on a network of timed automata and we present several relations to check the consistency of a contract in terms of realizability, to analyze whether an implementation satisfies the requirements defined on its contract, and to compare several implementations using the executed permissions as criteria.Comment: In Proceedings FLACOS 2012, arXiv:1209.169

Event Systems and Access Control

We consider the interpretations of notions of access control (permissions, interdictions, obligations, and user rights) as run-time properties of information systems specified as event systems with fairness. We give proof rules for verifying that an access control policy is enforced in a system, and consider preservation of access control by refinement of event systems. In particular, refinement of user rights is non-trivial; we propose to combine low-level user rights and system obligations to implement high-level user rights

Timed Automata Semantics for Visual e-Contracts

C-O Diagrams have been introduced as a means to have a more visual representation of electronic contracts, where it is possible to represent the obligations, permissions and prohibitions of the different signatories, as well as what are the penalties in case of not fulfillment of their obligations and prohibitions. In such diagrams we are also able to represent absolute and relative timing constraints. In this paper we present a formal semantics for C-O Diagrams based on timed automata extended with an ordering of states and edges in order to represent different deontic modalities.Comment: In Proceedings FLACOS 2011, arXiv:1109.239

Transferring Obligations Through Synchronizations

One common approach for verifying safety properties of multithreaded programs is assigning appropriate permissions, such as ownership of a heap location, and obligations, such as an obligation to send a message on a channel, to each thread and making sure that each thread only performs the actions for which it has permissions and it also fulfills all of its obligations before it terminates. Although permissions can be transferred through synchronizations from a sender thread, where for example a message is sent or a condition variable is notified, to a receiver thread, where that message or that notification is received, in existing approaches obligations can only be transferred when a thread is forked. In this paper we introduce two mechanisms, one for channels and the other for condition variables, that allow obligations, along with permissions, to be transferred from the sender to the receiver, while ensuring that there is no state where the transferred obligations are lost, i.e. where they are discharged from the sender thread but not loaded onto the receiver thread yet. We show how these mechanisms can be used to modularly verify deadlock-freedom of a number of interesting programs, such as some variations of client-server programs, fair readers-writers locks, and dining philosophers, which cannot be modularly verified without such transfer. We also encoded the proposed separation logic-based proof rules in the VeriFast program verifier and succeeded in verifying the mentioned programs

Contracts for Interacting Two-Party Systems

This article deals with the interrelation of deontic operators in contracts -- an aspect often neglected when considering only one of the involved parties. On top of an automata-based semantics we formalise the onuses that obligations, permissions and prohibitions on one party impose on the other. Such formalisation allows for a clean notion of contract strictness and a derived notion of contract conflict that is enriched with issues arising from party interdependence.Comment: In Proceedings FLACOS 2012, arXiv:1209.169

Designing compliant business processes with obligations and permissions. Business process management workshops.

The sequence and timing constraints on the activities in business processes are an important aspect of business process compliance. To date, these constraints are most often implicitly transcribed into control-flow-based process models. This implicit representation of constraints, however, complicates the verification, validation and reuse in business process design. In this paper, we investigate the use of temporal deontic assignments on activities as a means to declaratively capture the control-flow semantics that reside in business regulations and business policies. In particular, we introduce PENELOPE, a language to express temporal rules about the obligations and permissions in a business interaction, and an algorithm to generate compliant sequence-flow-based process models that can be used in business process design.

Social Ontology and Social Normativity

Many recent accounts of the ontology of groups, institutions, and practices have touched upon the normative or deontic dimensions of social reality (e.g., social obligations, claims, permissions, prohibitions, authority, and immunity), as distinct from any specifically moral values or obligations. For the most part, however, the ontology of such socio-deontic phenomena has not received the attention it deserves. In what sense might a social obligation or a claim exist? What is the ontological status of such an obligation (e.g., is it an entity in its own right)? And how do people come to have social obligations or permissions in the first place? In this dissertation, I argue that such social-deontic phenomena can be accounted for ontologically in terms of the existence of shared prescriptive representational content that is backed by collectively held dispositions to monitor for compliance, and to punish (sanction, blame, chide, look unfavorably upon) those who fail to comply