Towards Consistency-Based Reliability Assessment

International audienceMOTIVATION : Merging information provided by several sources is an important issue and merging techniques have been extensively studied. When the reliability of the sources is not known, one can apply merging techniques such as majority or arbitration merging or distancebasedmerging for solving conflicts between information. At the opposite, if the reliability of the sources is known, either represented in a quantitative or in a qualitative way, then it can be used to manage contradictions: information provided by a source is generally weakened or ignored if it contradicts information provided by a more reliable source [1, 4, 6]. Assessing the reliability of information sources is thus crucial. The present paper addresses this key question. We adopt a qualitative point of view for reliability representation by assuming that the relative reliability of information sources is represented by a total preorder. This works considers that we have no information about the sources and in particular, we do not know if they are correct (i.e they provide true information) or not. We focus on a preliminary stage of observation and assessment of sources. We claim that during that stage the key issue is a consistency analysis of information provided by sources, whether it is the consistency of single reports or consistency w.r.t trusted knowledge or the consistency of different reports together. We adopt an axiomatic approach: first we give some postulates which characterize what this reliability preorder should be, then we define a generic operator for building this preorder in agreement with the postulates

Consistency-Based Reliability Assessment

International audienceThis paper addresses the question of assessing the relative reliability of unknown information sources. We propose to consider a phase during which the consistency of information they report is analysed, whether it is the consistency of each single report, or the consistency of a report w.r.t. some trusted knowledge or the consistency of different reports together. We adopt an axiomatic approach by first giving postulates which characterize how the resulting reliability preorder should be; then we define a family of operators for building this preorder and demonstrate that it satisfies the proposed postulates

Agents adapt to majority behaviours

Agents within a group can have different perceptions of their working environment and autonomously fulfil their goals. However, they can be aware of beliefs and goals of the group as well as other members so that they can adjust their behaviours accordingly. To model these agents, we explicitly include knowledge commonly shared by the group and that obtained from other agents. By avoiding actions which violate ``mental attitudes'' shared by the majority of the group, agents demonstrate their social commitment to the group. Defeasible logic is chosen as our representation formalism for its computational efficiency, and for its ability to handle incomplete and conflicting information. Hence, our agents can enjoy the low computational cost while performing ``reasoning about others''. Finally, we present the implementation of our multi-agent system

Consistency-Based Reliability Assessment

This paper addresses the question of assessing the relative reliability of unknown information sources. We propose to consider a phase during which the consistency of information they report is analysed, whether it is the consistency of each single report, or the consistency of a report w.r.t. some trusted knowledge or the consistency of different reports together. We adopt an axiomatic approach by first giving postulates which characterize how the resulting reliability preorder should be; then we define a family of operators for building this preorder and demonstrate that it satisfies the proposed postulates

Weighted logics for artificial intelligence : an introductory discussion

International audienceBefore presenting the contents of the special issue, we propose a structured introductory overview of a landscape of the weighted logics (in a general sense) that can be found in the Artificial Intelligence literature, highlighting their fundamental differences and their application areas

Cyber-physical security of a chemical plant

The increasing number of cyber attacks on industries demands immediate attention for providing more secure mechanisms to safeguard industries and minimize risks. A supervisory control and data acquisition (SCADA) system employing the distributed networks of sensors and actuators that interact with the physical environment is vulnerable to attacks that target the interface between the cyber and physical subsystems. These cyber attacks are typically malicious actions that cause undesired results in the cyber physical world, for example, the Stuxnet attack that targeted Iran\u27s nuclear centrifuges. An attack that hijacks the sensors in an attempt to provide false readings to the controller can be used to feign normal system operation for the control system, while the attacker can hijack the actuators to send the system beyond its safety range. Cyber physical systems (CPS) being used in industries such as oil and gas, chemical process plants and the like are termed Industrial Control Systems (ICS). Control system security is aimed at preventing intentional or unintentional interference with the proper operation of ICS. This thesis proposes a process-aware approach with the use of invariant equations based on the physical and chemical properties of the process and a Multiple Security Domain Nondeducibility (MSDND) framework to detect when a sensor signal is being maliciously manipulated. We have taken a benzene production plant as case study to illustrate our approach and its effectiveness in determining the state of the system. A system without any MSDND secure information flows between the CPS and cyber monitors has fewer weaknesses that can be exploited --Abstract, page iii

An approach for formal analysis of the security of a water treatment testbed

This thesis focuses on securing critical infrastructures such as chemical plants, manufacturing units, and power generating plants against attacks that disrupt the information flow from one component to another. Such systems are controlled by an Industrial Control System (ICS) that includes controllers communicating with each other, and with physical sensors and actuators, using a communications network. Traditional security models partition the security universe into two worlds, secure and insecure, but in the real world the partitions often overlap and information is leaked even through the physical observation which makes it much harder to analyze a Cyber physical system (CPS). To overcome these, this thesis focus on the Multiple Security Domain Nondeducibility (MSDND) model to identify the vulnerable points of attack on the system that hide critical information as in the STUXNET virus rather than theft of information. It is shown how MSDND analysis, conducted on a realistic multi-stage water treatment testbed, is useful in enhancing the security of a water treatment plant. Based on the MSDND analysis, this thesis offers a thorough documentation on the vulnerable points of attack, invariants used for removing the vulnerabilities, and suggested design decisions that help in developing invariants --Abstract, page iii