Time and Temporal Reasoning

Guido Boella, Guido Governatori, Joris Hulstijn, Régis Riveret, Antonino Rotolo, and Leendert van der Torre.
Time and defeasibility in FIPA ACL semantics. In 2008 IEEE/WIC/ACM International Conference on Web Intelligence and Intelligent Agent Technology, pages 634-637. IEEE Press, 2008, Copyrigth © 2008 IEEE.
Abstract: Inferences about communicative actions are often conditional, non-monotonic, and involve the issue of time. Most agent communication languages, however, ignore these issues, due to the difficulty to combine them in a single formalism. This paper addresses such issues in defeasible logic, and illustrates how to express a semantics for ACLs in order to make non-monotonic inferences on the basis of communicative actions.
 
Guido Boella, Guido Governatori, Joris Hulstijn, Régis Riveret, Antonino Rotolo and Leemndert van der Torre.
FIPA Communicative Acts in Defeasible Logic. In Alankar Karol, Pavlos Peppas and Mary-Anne Williams, editor, Seventh IJCAI International Workshop on Nonmonotonic Reasoning, Action and Change (NRAC'07), Hyderabad, India, 7-8 January, 2007.
Abstract: In agent communication languages, the inferences that can be made on the basis of a communicative action are inherently conditional, and non-monotonic. For example, a proposal only leads to a commitment, on the condition that it is accepted. And in a persuasion dialogue, assertions may later be retracted. In this paper we therefore present a defeasible logic that can be used to express a semantics for agent communication languages, and to efficiently make inferences on the basis of communicative actions. The logic is non-monotonic, allows nested rules and mental attitudes as the content of communicative actions, and has an explicit way of expressing persistence over time. Moreover, it expresses that mental attitudes are publicly attributed to agents playing roles in the dialogue. To illustrate the usefulness of the logic, we reformalize the meta-theory underlying the FIPA semantics for agent communication, focusing on inform and propose. We show how composed speech acts can be formalized, and extend the semantics with an account of persuasion.
 
Guido Governatori, Joris Hulstijn, Régis Riveret, and Antonino Rotolo.
Characterising deadlines in temporal modal defeasible logic. In Mehmet A. Orgun and John Thornton, editors, 20th Australian Joint Conference on Artificial Intelligence, AI 2007, LNAI 4830, pages 486-496. Springer, 2007. Copyrigth © 2007 Springer.
Abstract: We provide a conceptual analysis of several kinds of deadlines, represented in Temporal Modal Defeasible Logic. The paper presents a typology of deadlines, based on the following parameters: deontic operator, maintenance or achievement, presence or absence of sanctions, and persistence after the deadline. The deadline types are illustrated by a set of examples.
 
Guido Governatori, Mehmet A. Orgun, and Chuchang Liu.
Modal tableaux for verifying stream authentication protocols. Journal of Autonomous Agents and Multi Agent Systems, 2008., Copyrigth © 2008 Springer.
Abstract: To develop theories to specify and reason about various aspects of multi-agent systems, many researchers have proposed the use of modal logics such as belief logics, logics of knowledge, and logics of norms. As multi-agent systems operate in dynamic environments, there is also a need to model the evolution of multi-agent systems through time. In order to introduce a temporal dimension to a belief logic, we combine it with a linear-time temporal logic using a powerful technique called fibring for combining logics. We describe a labelled modal tableaux system for the resulting fibred belief logic (FL) which can be used to automatically verify correctness of inter-agent stream authentication protocols. With the resulting fibred belief logic and its associated modal tableaux, one is able to build theories of trust for the description of, and reasoning about, multi-agent systems operating in dynamic environments.
 
Guido Governatori, Vineet Padmanabhan and Rotolo. Antonino.
Rule-Based Agents in Temporalised Defeasible Logic. In Qiang Yang and Geoff Webb, editor, Ninth Pacific Rim International Conference on Artificial Intelligence, Guilin, 7-11 August. pages 31-40. LNAI 4099. Springer, Berlin, 2006. The original publication is available atwww.springerlink.com
Abstract: This paper provides a framework based on temporal defeasible logic to reason about deliberative rule-based cognitive agents. Compared to previous works in this area our framework has the advantage that it can reason about temporal rules. We show that for rule-based cognitive agents deliberation is more than just deriving conclusions in terms of their mental components. Our paper is an extension of ai05,lpar05 in the area of cognitive agent programming
 
Guido Governatori and Antonino Rotolo.
Changing legal systems: Abrogation and annulment. Part I: Revision of defeasible theories. In Ron van der Meyden and Leon van der Torre, editors, 9th International Conference on Deontic Logic in Computer Science (DEON2008), Lecture Notes in Computer Science. Springer, 2008. Copyrigth © 2008 Springer.
Abstract: In this paper we investigate how to model legal abrogation and annulment in Defeasible Logic. We examine some options that embed in this setting, and similar rule-based systems, ideas from belief and base revision. In both cases, our conclusion is negative, which suggests to adopt a different logical model.
 
Guido Governatori and Antonino Rotolo.
Changing legal systems: Abrogation and annulment. Part II: Temporalised defeasible logic. In Guido Boella, Harko Verhagen, and Muindhar Singh, editors, Proceedings of Normative Multi Agent Systems (NorMAS 2008, Luxembourg 15-16 July 2008.
Abstract: In this paper we propose a temporal extension of Defeasible Logic to model legal modifications, such as abrogation and annulment. Hence, this framework overcomes the difficulty, discussed elsewhere \cite{deon-part1}, of capturing these modification types using belief and base revision.
 
Guido Governatori, Antonino Rotolo, Régis Riveret, Monica Palmirani and Giovanni Sartor.
Variations of Temporal Defeasible Logic for Modelling Norm Modifications. In Radboud Winkels, editor, Proceedings of 11th International Conference on Artificial Intelligence and Law, pp. 155-159. ACM Press, New York, 2007. Copyright © 2007 ACM
Abstract: This paper proposes some variants of Temporal Defeasible Logic (TDL) to reason about normative modifications. These variants make it possible to differentiate cases in which, for example, modifications at some time change legal rules but their conclusions persist afterwards from cases where also their conclusions are blocked.
 
Guido Governatori, Antonino Rotolo and Giovanni Sartor.
Temporalised Normative Positions in Defeasible Logic. In Anne Gardner, editor, 10th International Conference on Artificial Intelligence and Law (ICAIL05), Bologna, June 6-11, pages 25-34. ACM Press, 2005. Copyright © ACM Press
Abstract: We propose a computationally oriented non-monotonic multi-modal logic arising from the combination of temporalised agency and temporalised normative positions. We argue about the defeasible nature of these notions and then we show how to represent and reason with them in the setting of Defeasible Logic.
 
Guido Governatori and Paolo Terenziani.
Temporal extensions to defeasible logic. In Mehmet A. Orgun and John Thornton, editors, 20th Australian Joint Conference on Artificial Intelligence, AI 2007, LNAI 4830, pages 476-485. Springer, 2007. Copyrigth © 2007 Springer.
Abstract: In this paper, we extend Defeasible Logic (a computationally-oriented non-monotonic logic) in order to deal with temporalised rules. In particular, we extend the logic to cope with durative facts, as well as with delays between the antecedent and the consequent of rules. We showed that the extended temporalised framework is suitable to model different types of causal relations which have been identified by the specialised literature. We also prove that the computational properties of the original logic are still retained by the extended approach.
 
Ruopeng Lu, Shazia Sadiq and Guido Governatori.
Utilizing Successful Work Practice for Business Process Evolution. In Witold Abramowicz and Heinrich C. Mayr, editors, Business Information Systems (BIS 2006), Klagenfurt, Austria, May 31-June 2. pages 58-76. LNI 85. GI, Berlin, 2006. Copyright © GI
Abstract: Business process management (BPM) has emerged as a dominant technology in current enterprise systems and business solutions. However, business processes are always evolving in current dynamic business environments where requirements and goals are constantly changing. Whereas literature reports on the importance of domain experts in process modelling and adaptations, current solutions have not addressed this issue effectively. In this paper, we present a framework that utilizes successful work practice to support business process evolution. The framework on one hand provides the ability to use domain expert knowledge and experience to tailor individual process instances according to case specific requirements; and on the other, provides a means of using this knowledge through learning techniques to guide subsequent process changes.
 
Ruopeng Lu, Shazia Sadiq, and Guido Governatori.
On managing business processes variants. Data and Knowledge Engineering, 2009.
Abstract: Variance in business process execution can be the result of several situations, such as disconnection between documented models and business operations, workarounds in spite of process execution engines, dynamic change and exception handling, flexible and ad-hoc requirements, and collaborative and/or knowledge intensive work. It is imperative that effective support for managing process variances be extended to organizations mature in their BPM (Business Process Management) uptake so that they can ensure organization wide consistency, promote reuse and capitalize on their BPM investments. This paper presents an approach for managing business processes that is conducive to dynamic change and the need for flexibility in execution. The approach is based on the notion of process constraints. It further provides a technique for effective utilization of the adaptations manifested in process variants. In particular, we will present a facility for discovery of preferred variants through effective search and retrieval based on the notion of process similarity, where multiple aspects of the process variants are compared according to specific query requirements. The advantage of this approach is the ability to provide a quantitative measure for the similarity between process variants, which further facilitates various BPM activities such as process reuse, analysis and discovery.
 
Ruopeng Lu, Shazia Sadiq, Guido Governatori, and Xiaoping Yang.
Defining adaptation constraints for business process variants. In 12th International Conference on Business Information Systems, Lecture Notes in Business Information Processing 7. Springer, 2009, Copyrigth © 2009 Springer.
Abstract: In current dynamic business environment, it has been argued that certain characteristics of ad-hocism in business processes are desirable. Such business processes typically have a very large number of instances, where design decisions for each process instance may be made at runtime. In these cases, predictability and repetitiveness cannot be counted upon, as the complete process knowledge used to define the process model only becomes available at the time after a specific process instance has been instantiated. The basic premise is that for a class of business processes it is possible to specify a small number of essential constraints at design time, but allow for a large number of execution possibilities at runtime. The objective of this paper is to conceptualise a set of constraints for process adaptation at instance level. Based on a comprehensive modelling framework, business requirements can be transformed to a set of minimal constraints, and the support for specification of process constraints and techniques to ensure constraint quality are developed.
 
Ruopeng Lu, Shazia Sadiq, Vineet Padmanabhan and Guido Governatori.
Using a Temporal Constraint Network for Business Process Execution. In Gillian Dobbie and James Bailey, editor, Seventeenth Australasian Database Conference (ADC2006), Hobart, Australia, 16-19 January. pages 157-166. CRPIT. ACS, Sydney, 2006. Copyright © ACS
Abstract: Business process management (BPM) has emerged as a dominant technology in current enterprise systems and business solutions. However, the technology continues to face challenges in coping with dynamic business environments where requirements and goals are constantly changing. In this paper, we present a modelling framework for business processes that is conducive to dynamic change and the need for flexibility in execution. This framework is based on the notion of process constraints. Process constraints may be specified for any aspect of the process, such as task selection, control flow, resource allocation, etc. Our focus in this paper is on a set of scheduling constraints that are specified through a temporal constraint network. We will demonstrate how this specification can lead to increased flexibility in process execution, while maintaining a desired level of control. A key feature and strength of the approach is to use the power of constraints, while still preserving the intuition and visual appeal of graphical languages for process modelling.
 
Mehmet A. Orgun, Guido Governatori and Chuchang Liu.
Modal Tableaux for Verifying Security Protocols. In Barbara Dunin-Keplicz and Rineke Verbrugge, editor, Formal Approaches to Multi-Agent Systems (FAMAS 2006), Riva del Garda, Italy, 28 August - 1 September. pages 31-46. 2006.
Abstract: To develop theories to specify and reason about various aspects of multi-agent systems, many researchers have proposed the use of modal logics such as belief logics, logics of knowledge, and logics of norms. As multi-agent systems operate in dynamic environments, there is also a need to model the evolution of multi-agent systems through time. In order to introduce a temporal dimension to a belief logic, we combine it with a linear-time temporal logic using a powerful technique called fibring for combining logics. We describe a labelled modal tableaux system for a fibred belief logic (FL) which can be used to automatically verify correctness of inter-agent stream authentication protocols. With the resulting fibred belief logic and its associated modal tableaux, one is able to build theories of trust for the description of, and reasoning about, multi-agent systems operating in dynamic environments.
 
Mehmet A. Orgun, Ji Ma, Chuchang Liu and Guido Governatori.
Analysing Stream Authentication Protocols in Autonomous Agent-Based Systems. In 2nd IEEE International Symposium on Dependable, Autonomic and Secure Computing (DASC'06), Indiana University, Purdue University, Indianapolis, USA, September 29--October 1. pages 325-332. IEEE Press, Los Alamitos, 2006. Copyright © IEEE Press
Abstract: In stream authentication protocols used for large-scale data dissemination in autonomuous systems, authentication is based on the timing of the publication of keys, and depends on trust of the receiver in the sender and belief on whether an intruder can have prior knowledge of a key before it is published by a protocol. Many existing logics and approaches have successfully been applied to specify other types of authentication protocols, but most of them are not appropriate for analysing stream authentication protocols. We therefore consider a fibred modal logic that combines a belief logic with a linear-time temporal logic which can be used to analyse time-varying aspects of certain problems. With this logical system one is able to build theories of trust for analysing stream authentication protocols, which can deal with not only agent beliefs but also the timing properties of an autonomous agent-based system.
 
Régis Riveret, Guido Governatori and Antonino Rotolo.
Argumentation Semantics for Temporal Defeasible Logic. In Loris Penserini, Pavlos Peppas and Anna Perini, editor, Third European Starting AI Researcher Symposium (STAIRS 2006), Riva del Garda, 28-29 August. pages 267-268. Frontiers in Artificial Intelligence and Applications 142. IOS Press, Amsterdam, 2006.
Abstract: We present an extension of the argumentation semantics for defeasible logic to cover the temporalisation of defeasible logic with permanent and immanent temporal literals
 
Régis Riveret, Antonino Rotolo and Guido Governatori.
Interaction between Normative Systems and Cognitive agents in Temporal Modal Defeasible Logic. In Guido Boella, Leon van der Torre and Harko Verhagen, editors, Normative Multi-agent Systems. Dagstuhl Seminar Proceedings 7122. Internationales Begegnungs- und Forschungszentrum fuer Informatik (IBFI), Schloss Dagstuhl, Germany, Dagstuhl, Germany, 2007.
Abstract: While some recent frameworks on cognitive agents addressed the combination of mental attitudes with deontic concepts, they commonly ignore the representation of time. We propose in this paper a variant of Temporal Modal Defeasible Logic to deal in particular with temporal intervals.
 
Insu Song and Guido Governatori.
Hardware Implementation of Temporal Nonmonotonic Logics. In Abdul Sattar and Byeong Ho Kang, editor, 19th Australian Joint Conference on Artificial Intelligence, Hobart, 4-8 December. pages 808-817. Lecture Notes in Computer Science 4304. Springer, Berlin, 2006. The original publication is available at www.springerlink.com
Abstract: In order to apply nonmonotonic logics for specifying industrial automation controllers, we define (1) a method to extend atemporal nonmonotonic logics with temporal operators and (2) a mapping of these new temporal nonmonotonic logics into a Metric Temporal Logic. This mapping provides a formal specification method for real-time temporal reasoning digital circuits for the temporal nonmonotonic logics. We present our method in the context of synthesizing custom digital hardware (called agent chip) automatically from high level agent specifications.
 
Bela Stantic, Guido Governatori Abdul Sattar.
Handling of Current Time in Native XML Databases. In Gillian Dobbie & James Bailey, editor, Seventeenth Australasian Database Conference (ADC2006), Hobart, Australia. pages 175-182. CRPIT. ACS, Sydney, 2006. Copyright © ACS
Abstract: The introduction of Native XML databases opens many research questions related to the data models used to represent and manipulate data, including temporal data in XML. Increasing use of XML for Valid Web pages warrants an adequate treatment of now in Native XML databases. In this study, we examined how to represent and manipulate now-relative temporal data. We identify different approaches being used to represent current time in XML temporal databases, and introduce the notion of storing variables such as `now' or `UC' as strings in XML native databases. All approaches are empirically evaluated on a query that time-slices the timeline at the current time. The experimental results indicate that the proposed extension offers several advantages over other approaches: better semantics, less storage space and better response time.