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Nico Roos

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18 papers
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18

ECAI Conference 2014 Conference Paper

An argumentation system for reasoning with LPm

  • Wenzhao Qiao
  • Nico Roos

Inconsistent knowledge-bases can entail useful conclusions when using the three-valued semantics of the paraconsistent logic LP. However, the set of conclusions entailed by a consistent knowledge-base under the three-valued semantics is smaller than set of conclusions entailed by the knowledge-base under a two-valued semantics. Preferring conflict-minimal interpretations of the logic LP; i. e. , LPm, reduces the gap between these two sets of conclusions.

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ECAI Conference 2014 Conference Paper

The semantics of behavior

  • Nico Roos

The BDI architecture is one of the most popular architectures for agents with symbolic reasoning capabilities. To formally define the notions of Beliefs, Desires and Intentions, different formal logics have been proposed in the literature. Although these proposals often refer to the work of Bratman [2], none, however, correctly capture the form of practical reasoning that Bratman describes. What is lacking, is a proper characterization of the agent's behavior. The formal logics proposed so far, do not allow for an adequate characterization of the refinement of behaviors that Bratman describes.

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AAAI Conference 2012 Conference Paper

Exploiting Shared Resource Dependencies in Spectrum Based Plan Diagnosis

  • Shekhar Gupta
  • Nico Roos
  • Cees Witteveen
  • Bob Price
  • Johan DeKleer

In case of a plan failure, plan-repair is a more promising solution than replanning from scratch. The effectiveness of plan-repair depends on knowledge of which plan action failed and why. Therefore, in this paper, we propose an Extended Spectrum Based Diagnosis approach that efficiently pinpoints failed actions. Unlike Model Based Diagnosis (MBD), it does not require the fault models and behavioral descriptions of actions. Our approach first computes the likelihood of an action being faulty and subsequently proposes optimal probe locations to refine the diagnosis. We also exploit knowledge of plan steps that are instances of the same plan operator to optimize the selection of the most informative diagnostic probes. In this paper, we only focus on diagnostic aspect of planrepair process.

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AAMAS Conference 2009 Conference Paper

Stable Multi-project Scheduling of Airport Ground Handling Services by Heterogeneous Agents

  • Xiaoyu Mao
  • Nico Roos
  • Alfons Salden

This paper addresses decentralized multi-project scheduling under uncertainty. The problem instance we study is the scheduling of airport ground handling services, where aircraft turnarounds can be seen as multiple projects, ground handling services as activities, and service providers as resources. In this environment aircraft requiring ground handling services and the corresponding service providers are self-interested autonomous parties. Moreover, the environment is well-known for its large number of disturbances. We employ a heterogeneous multiagent scheduling framework with two types of autonomous agents representing aircraft and ground service providers respectively. We use online scheduling to cope with uncertainty in the release time of project: the uncertainty in aircraft arrival time at an airport. To balance the interests of the two types of agents in this heterogeneous multiagent system, we propose a marketbased mechanism to assign time slots to aircraft turnaround activities. We study the use of this mechanism in a cooperative and a non-cooperative setting. In a dynamic environment such as airport ground handling, the execution of project schedules may be invalidated by various disruptions. As a result project agents may incur high costs if they have to reschedule some of their activities. The insertion of slack time between activities is a well known solution. The delay cost incurred by inserting slack should balance the expected costs of rescheduling some activities. Since in a dynamic multiagent system it is hard to analytically calculate optimal slack time between activities, we propose that agents determine these slack time using a co-evolutionary learning approach. Experiment show that our decentralized scheduling approach scores on average as high as well-established ORbased heuristics, and that slack times to keep a schedule stable can be learned.

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ECAI Conference 2008 Conference Paper

Diagnosis of Simple Temporal Networks

  • Nico Roos
  • Cees Witteveen

In many domains successful execution of plans requires careful monitoring and repair. Diagnosis of plan execution supports this process by identifying causes of plan failure.

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AAMAS Conference 2008 Conference Paper

Multi-Agent Plan Diagnosis and Negotiated Repair

  • Huib Aldewereld
  • Pieter Buzing
  • Geert Jonker
  • Femke de Jonge
  • Frank Dignum
  • John-Jules Ch. Meyer
  • Nico Roos
  • Cees Witteveen

In the complex, dynamic domain of Air Traffic Control (ATC) many unexpected events can happen during the execution of a plan. Sometimes these disruptions make the plan infeasible and require a change of the original plan. Unexpected events may disrupt the execution of a plan leading to conflicts concerning the use of shared resources. By monitoring the possibly disrupted execution of a plan, air traffic controllers identify and repair conflicts before they occur, making the plan ‘healthy’ again. Model-based diagnosis helps to identify the causes of observed disruptions in the execution of a plan. This information enables the creation of better plan repairs. These repairs should efficient, but moreover they should be fair, i. e. , one airline should not be the victim of conflicts caused by another. Due to the complexity of planning tasks, it is beneficial to provide a distributed solution such that the workload is spread instead of centralised. Moreover, since the choice between various possible solutions to a conflict in the plan execution directly influence different parties (with diverting interests), the decision about which solution to choose should not be made by a single (central) decision maker, but agreed upon by the different parties involved. The Multi-Agent Diagnosis and negotiated repair (MAD) demonstrator combines our previous research done on model-based diagnosis, planning and scheduling techniques, and methods for multi-agent negotiation to solve this problem in a distributed manner. The resulting tool is a system to support the control and adaptation of distributed plan execution in the domain of ATC.

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JAAMAS Journal 2008 Journal Article

Primary and secondary diagnosis of multi-agent plan execution

  • Femke de Jonge
  • Nico Roos
  • Cees Witteveen

Abstract Diagnosis of plan failures is an important subject in both single- and multi-agent planning. Plan diagnosis can be used to deal with plan failures in three ways: (i) to provide information necessary for the adjustment of the current plan or for the development of a new plan, (ii) to point out which equipment and/or agents should be repaired or adjusted to avoid further violation of the plan execution, and (iii) to identify the agents responsible for plan-execution failures. We introduce two general types of plan diagnosis: primary plan diagnosis identifying the incorrect or failed execution of actions, and secondary plan diagnosis that identifies the underlying causes of the faulty actions. Furthermore, three special cases of secondary plan diagnosis are distinguished, namely agent diagnosis, equipment diagnosis and environment diagnosis.

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AAMAS Conference 2007 Conference Paper

Diagnosis of Plan Step Errors and Plan Structure Violations

  • Cees Witteveen
  • Nico Roos
  • Adriaan ter Mors
  • Xiaoyu Mao

Failures in plan execution can be attributed to errors in the execution of plan steps or violations of the plan structure. While in previous work we have concentrated on the first type of failures, in this paper we introduce the idea of diagnosing violations in the plan structure. The structure of a plan prescribes which actions have to be performed and which precedence constraints between them have to be respected. Especially in multi-agent environments violations of plan structure might easily occur as the consequence of synchronization errors. Using a formal framework for plan diagnosis, we show how Model-Based Diagnosis can applied to identify these violations of plan structure specifications and we analyze the computational complexity of the associated diagnostic problems.

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JAAMAS Journal 2007 Journal Article

Models and methods for plan diagnosis

  • Nico Roos
  • Cees Witteveen

Abstract We consider a model-based diagnosis approach to the diagnosis of plans. Here, a plan performed by some agent(s) is considered as a system to be diagnosed. We introduce a simple formal model of plans and plan execution where it is assumed that the execution of a plan can be monitored by making partial observations of plan states. These observed states are used to compare them with states predicted based on (normal) plan execution. Deviations between observed and predicted states can be explained by qualifying some plan steps in the plan as behaving abnormally. A diagnosis is a subset of plan steps qualified as abnormal that can be used to restore the compatibility between the predicted and the observed partial state. Besides minimum and subset minimal diagnoses, we argue that in plan-based diagnosis maximum informative diagnoses should be considered as preferred diagnoses, too. The latter ones are diagnoses that make the strongest predictions with respect to partial states to be observed in the future. We show that in contrast to minimum diagnoses, finding a (subset minimal) maximum informative diagnosis can be achieved in polynomial time. Finally, we show how these diagnoses can be found efficiently if the plan is distributed over a number of agents.

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AIJ Journal 1998 Journal Article

Reasoning by cases in default logic

  • Nico Roos

Reiter's Default Logic is one of the most popular formalisms for describing default reasoning. One important defect of Default Logic is, however, the inability to reason by cases. Over the years, several solutions for this problem have been proposed. All these proposals deal with deriving new propositions through reasoning by cases. None, however, discuss the propositions that should no longer be derivable as a result of reasoning by cases. This paper discusses the latter subject. It shows that an intuitively plausible way of dealing with propositions that should no longer be derivable as a result of reasoning by cases, can have far reaching consequences. One of the consequences is that disjunctions must be viewed as describing possible extensions.

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AIJ Journal 1992 Journal Article

A logic for reasoning with inconsistent knowledge

  • Nico Roos

In many situations humans have to reason with inconsistent knowledge. These inconsistencies may occur due to not fully reliable sources of information. In order to reason with inconsistent knowledge, it is not possible to view a set of premisses as absolute truths as is done in predicate logic. Viewing the set of premisses as a set of assumptions, however, it is possible to deduce useful conclusions from an inconsistent set of premisses. In this paper a logic for reasoning with inconsistent knowledge is described. This logic is a generalization of the work of Rescher [12]. In the logic a reliability relation is used to choose between incompatible assumptions. These choices are only made when a contradiction is derived. As long as no contradiction is derived, the knowledge is assumed to be consistent. This makes it possible to define an executable deduction process for the logic. For the logic a semantics based on the ideas of Shoham [14, 15] is defined. It turns out that the semantics for the logic is a preferential semantics according to the definition of Kraus, Lehmann and Magidor [9]. Therefore the logic is a logic of system P and possesses all the properties of an ideal nonmonotonic logic.

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v2026.09.13