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Haythem O. Ismail

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4 papers

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JELIA Conference 2021 Conference Paper

Trust Is All You Need: From Belief Revision to Information Revision

Yasser Ammar
Haythem O. Ismail

Abstract Belief revision is a hallmark of knowledge representation, logic, and philosophy. However, despite the extensive research in the area, we believe a fresh take on belief revision is needed. To that end, it is our conviction that believing a piece of information depends on trust in information sources that conveyed said piece and that trust in information sources is affected by changes in beliefs. Trust is also an impress of philosophy and all time favorite of psychology and multi-agent systems. Hence, many approaches were developed for trust representation, yet, in isolation from belief revision. While admittedly crucial to a realistic treatment of belief revision, trust revision, to our dismay, did not receive the same level of attention. In this paper, we argue that a formal treatment for the joint interdependent revision of belief and trust is called for. Moreover, we propose a new framework called information revision that captures the joint revision of belief and trust. Further, we provide postulates that govern such process of revision. Finally, we provide a class of operators called relevant change propagation operators and provide their representation theorem.

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TARK Conference 2019 Conference Paper

A Unified Algebraic Framework for Non-Monotonicity

Nourhan Ehab
Haythem O. Ismail

Tremendous research effort has been dedicated over the years to thoroughly investigate non-monotonic reasoning. With the abundance of non-monotonic logical formalisms, a unified theory that enables comparing the different approaches is much called for. In this paper, we present an algebraic graded logic we refer to as LogAG capable of encompassing a wide variety of non-monotonic formalisms. We build on Lin and Shoham's argument systems first developed to formalize non-monotonic commonsense reasoning. We show how to encode argument systems as LogAG theories, and prove that LogAG captures the notion of belief spaces in argument systems. Since argument systems capture default logic, autoepistemic logic, the principle of negation as failure, and circumscription, our results show that LogAG captures the before-mentioned non-monotonic logical formalisms as well. Previous results show that LogAG subsumes possibilistic logic and any non-monotonic inference relation satisfying Makinson's rationality postulates. In this way, LogAG provides a powerful unified framework for non-monotonicity.

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ECAI Conference 2010 Conference Paper

High-Level Perception as Focused Belief Revision

Haythem O. Ismail
Nasr Kasrin

We present a framework for incorporating perception-induced beliefs into the knowledge base of a rational agent. Normally, the agent accepts the propositional content of perception and other propositions that follow from it. Given the fallibility of perception, this may result in contradictory beliefs. Hence, we model high-level perception as belief revision. We overcome difficulties imposed by the highly idealistic classical belief revision in two ways. First, we adopt a belief revision operator based on relevance logic, thus limiting the derived beliefs to those that relevantly follow from the new percept. Second, we focus belief revision on only a subset of the agent's set of beliefs-those that we take to be within the agent's current focus of attention.

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AAAI Conference 2000 Short Paper

Reasoning and Acting in Time

Haythem O. Ismail

A natural language competent embodied cognitive agent should satisfy two requirements. First, it should interleave reasoning and acting in a changing world where errors and interrupts may occur. Second, it should be able to communicate in natural language about the past, present, and future states of its environment. This imposes certain restrictions on the logic and reasoning engine used by the agent. The logical language needs to be suitable for representing natural language utterances, knowledge about acts, and perceptual information. In addition, it should include a representation of the notion of the present that reflects the semantics of the English "now". In our model, the present is represented by a NOW pointer that moves whenever the agent senses a change in the world. Reasoning problems emerge when the agent is reasoning about NOW, and the very process of reasoning results in NOW moving.

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