Papers and Publications, Center of Excellence in Command, Control, Communications, and Intelligence
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This collection contains papers written by members and fellows of the C4I Center.
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Browsing Papers and Publications, Center of Excellence in Command, Control, Communications, and Intelligence by Subject "Bayesian networks"
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Item An Application of Bayesian Networks to Antiterrorism Risk Management for Military Planners(2005-11-18T20:51:11Z) Hudson, Linwood D.; Ware, Bryan S.; Laskey, Kathryn B.; Mahoney, Suzanne M.Recent events underscore the need for effective tools for managing the risks posed by terrorists. Assessing the threat of terrorist attack requires combining information from multiple disparate sources, most of which involve intrinsic and irreducible uncertainties. This paper describes Site Profiler® Installation Security Planner, a tool initially built to assist antiterrorism planners at military installations to draw inferences about the risk of terrorist attack. Site Profiler applies knowledge-based Bayesian network construction to allow users to manage a portfolio of hundreds of threat/asset pairs. The constructed networks combine evidence from analytic models, simulations, historical data, and user judgments. Site Profiler was constructed using our generic application development environment that combines a dynamically generated object model, a Bayesian inference engine, a graphical editor for defining the object model, and persistent storage for a knowledge base of Bayesian network fragment objects. Site Profiler's human-computer interaction system is tailored to mathematically unsophisticated users. Future extensions to Site Profiler will use data warehousing to allow analysis and validation of the network’s ability to predict the most effective antiterrorism risk management solutions.Item Bayesian ontologies in AI systems(2006-07-30T03:10:44Z) Costa, Paulo C. G.; Laskey, Kathryn B.; AlGhamdi, GhaziOntologies have become ubiquitous in current-generation information systems. An ontology is an explicit, formal representation of the entities and relationships that can exist in a domain of application. Following a well-trodden path, initial research in computational ontology has neglected uncertainty, developing almost exclusively within the framework of classical logic. As appreciation grows of the limitations of ontology formalisms that cannot represent uncertainty, the demand from user communities increases for ontology formalisms with the power to express uncertainty. Support for uncertainty is essential for interoperability, knowledge sharing, and knowledge reuse. Bayesian ontologies are used to describe knowledge about a domain with its associated uncertainty in a principled, structured, sharable, and machine-understandable way. This paper considers Multi-Entity Bayesian Networks (MEBN) as a logical basis for Bayesian ontologies, and describes PR-OWL, a MEBN-based probabilistic extension to the ontology language OWL. To illustrate the potentialities of Bayesian probabilistic ontologies in the development of AI systems, we present a case study in information security, in which ontology development played a key role.Item Credibility Models for Multi-Source Fusion(2006-07) Wright, Edward J.; Laskey, Kathryn B.This paper presents a technical approach for fusing information from diverse sources. Fusion requires appropriate weighting of information based on the quality of the source of the information. A credibility model characterizes the quality of information based on the source and the circumstances under which the information is collected. In many cases credibility is uncertain, so inference is necessary. Explicit probabilistic credibility models provide a computational model of the quality of the information that allows use of prior information, evidence when available, and opportunities for learning from data. This paper provides an overview of the challenges, describes the advanced probabilistic reasoning tools used to implement credibility models, and provides an example of the use of credibility models in a multi-source fusion process.Item MEBN: A Logic for Open-World Probabilistic Reasoning(2006-02-03T18:07:33Z) Laskey, Kathryn B.Uncertainty is a fundamental and irreducible aspect of our knowledge about the world. Probability is the most well-understood and widely applied logic for computational scientific reasoning under uncertainty. As theory and practice advance, general-purpose languages are beginning to emerge for which the fundamental logical basis is probability. However, such languages have lacked a logical foundation that fully integrates classical first-order logic with probability theory. This paper presents such an integrated logical foundation. A formal specification is presented for multi-entity Bayesian networks (MEBN), a knowledge representation language based on directed graphical probability models. A proof is given that a probability distribution over interpretations of any consistent, finitely axiomatizable first-order theory can be defined using MEBN. A semantics based on random variables provides a logically coherent foundation for open world reasoning and a means of analyzing tradeoffs between accuracy and computation cost. Furthermore, the underlying Bayesian logic is inherently open, having the ability to absorb new facts about the world, incorporate them into existing theories, and/or modify theories in the light of evidence. Bayesian inference provides both a proof theory for combing prior knowledge with observations, and a learning theory for refining a representation as evidence accrues. The results of this paper provide a logical foundation for the rapidly evolving literature on first-order Bayesian knowledge representation, and point the way toward Bayesian languages suitable for general-purpose knowledge representation and computing. Because first-order Bayesian logic contains classical first-order logic as a deterministic subset, it is a natural candidate as a universal representation for integrating domain ontologies expressed in languages based on classical first-order logic or subsets thereof.Item Modeling Insider Behavior Using Multi-Entity Bayesian Networks(2006-03-06T15:01:08Z) AlGhamdi, Ghazi; Laskey, Kathryn B.; Wright, Edward J.; Barbará, Daniel; Chang, K.C.This paper tackles a key aspect of the information security problem: modeling the behavior of insider threats. The specific problem addressed by this paper is the identification of malicious insider behavior in trusted computing environments. Although most security techniques in intrusion detection systems (IDS’s) focus on protecting the system boundaries from outside attacks, defending against an insider who attempts to misuse privileges is an equally significant problem for network security. It is usually assumed that users who are given access to network resources can be trusted. However, the eighth annual CSI/FBI 2003 report found that insider abuse of network access was the most cited form of attack or abuse. 80% of respondents were concerned about insider abuse, although 92% of the responding organizations employed some form of access control mechanism [7]. Therefore, though insider users are legally granted access to network resources, it is essential to protect against misuse by insiders. This paper presents a scalable model to represent insider behavior. We provide simulation experiments to demonstrate the ability of the model to detect threat behavior. Information security objectives can be accomplished through a layered approach that represents several lines of defense. This approach constitutes one of these lines of defense.Item PR-OWL: A Framework for Bayesian Ontologies(IOS Press, 2006-11) Costa, Paulo C.G.; Laskey, Kathryn B.Across a wide range of domains, there is an urgent need for a wellfounded approach to incorporating uncertain and incomplete knowledge into formal domain ontologies. Although this subject is receiving increasing attention from ontology researchers, there is as yet no broad consensus on the definition of a probabilistic ontology and on the most suitable approach to extending current ontology languages to support uncertainty. This paper presents two contributions to developing a coherent framework for probabilistic ontologies: (1) a formal definition of a probabilistic ontology, and (2) an extension of the OWL Web Ontology Language that is consistent with our formal definition. This extension, PR-OWL, is based on Multi-Entity Bayesian Networks (MEBN), a first-order Bayesian logic that unifies Bayesian probability with First-Order Logic. As such, PR-OWL combines the full representation power of OWL with the flexibility and inferential power of Bayesian logic.