108,044 research outputs found
Updates by Reasoning about States
It has been argued that some sort of control must be introduced in order to perform update operations in deductive databases. Indeed, many approaches rely on a procedural semantics of rule based languages and often perform updates as side-effects. Depending on the evaluation procedure, updates are generally performed in the body (top-down evaluation) or in the head of rules (bottom-up evaluation). We demonstrate that updates can be specified in a purely declarative manner using standard model based semantics without relying on procedural aspects of program evaluation. The key idea is to incorporate states as first-class objects into the language. This is the source of the additional expressiveness needed to define updates. We introduce the update language Statelog+-, discuss various domains of application and outline how to implement computation of the perfect model semantics for Statelog+- programs
Hidden protocols: Modifying our expectations in an evolving world
When agents know a protocol, this leads them to have expectations about future observations. Agents can update their knowledge by matching their actual observations with the expected ones. They eliminate states where they do not match. In this paper, we study how agents perceive protocols that are not commonly known, and propose a semantics-driven logical framework to reason about knowledge in such scenarios. In particular, we introduce the notion of epistemic expectation models and a propositional dynamic logic-style epistemic logic for reasoning about knowledge via matching agentsÊ expectations to their observations. It is shown how epistemic expectation models can be obtained from epistemic protocols. Furthermore, a characterization is presented of the effective equivalence of epistemic protocols. We introduce a new logic that incorporates updates of protocols and that can model reasoning about knowledge and observations. Finally, the framework is extended to incorporate fact-changing actions, and a worked-out example is given. © 2013 Elsevier B.V
A Dynamic Epistemic Logic for Abstract Argumentation
This paper introduces a multi-agent dynamic epistemic logic for abstract argumenta-
tion. Its main motivation is to build a general framework for modelling the dynamics
of a debate, which entails reasoning about goals, beliefs, as well as policies of com-
munication and information update by the participants. After locating our proposal
and introducing the relevant tools from abstract argumentation, we proceed to build a
three-tiered logical approach. At the first level, we use the language of propositional
logic to encode states of a multi-agent debate. This language allows to specify which
arguments any agent is aware of, as well as their subjective justification status. We
then extend our language and semantics to that of epistemic logic, in order to model
individuals’ beliefs about the state of the debate, which includes uncertainty about the
information available to others. As a third step, we introduce a framework of dynamic
epistemic logic and its semantics, which is essentially based on so-called event models
with factual change. We provide completeness results for a number of systems and
show how existing formalisms for argumentation dynamics and unquantified uncerSynthese
tainty can be reduced to their semantics. The resulting framework allows reasoning
about subtle epistemic and argumentative updates—such as the effects of different
levels of trust in a source—and more in general about the epistemic dimensions of
strategic communication
State-of-the-art on evolution and reactivity
This report starts by, in Chapter 1, outlining aspects of querying and updating resources on
the Web and on the Semantic Web, including the development of query and update languages
to be carried out within the Rewerse project.
From this outline, it becomes clear that several existing research areas and topics are of
interest for this work in Rewerse. In the remainder of this report we further present state of
the art surveys in a selection of such areas and topics. More precisely: in Chapter 2 we give
an overview of logics for reasoning about state change and updates; Chapter 3 is devoted to briefly describing existing update languages for the Web, and also for updating logic programs;
in Chapter 4 event-condition-action rules, both in the context of active database systems and
in the context of semistructured data, are surveyed; in Chapter 5 we give an overview of some relevant rule-based agents frameworks
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