Nico Roos

Nico Roos
Maastricht University | UM · Department of Advanced Computing Sciences

Dr. Ir. Ing.

About

94
Publications
9,494
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801
Citations
Additional affiliations
January 1995 - December 2012
Maastricht University
August 1991 - August 1997
Research Institute for Knowledge Systems
Research Institute for Knowledge Systems
Position
  • Consultant

Publications

Publications (94)
Article
Full-text available
Reiter's Default Logic [14] 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, howe...
Article
Full-text available
Models used for Model-Based Diagnosis usually assume that observations, and predictions based on the system description are accurate. In some domains, however, this assumption is invalid. Observations may not be accurate or the behavior model of the system does not allow for accurate predictions. Therefore, the accuracy of predictions, which is a f...
Article
Full-text available
Diagnosis of plan failures is an important subject in both single- and multi-agent planning. Plan diag- nosis may provide information that can improve the way the plan failures are dealt with in three ways: (i) it provides information necessary for the adjust- ment of the current plan or for the development of a new plan, (ii) it can be used to poi...
Article
Full-text available
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,...
Article
Full-text available
Humans can make a plan by refining abstract actions. Dynamic logic, which enables reasoning about the dynamics of actions, does not support this form of planning. This paper investigates the extension of dynamic logic with a refinement relation that specifies how an abstract action can be refined into a more specific (composite) action. The paper i...
Preprint
Full-text available
Learning arguments is highly relevant to the field of explainable artificial intelligence. It is a family of symbolic machine learning techniques that is particularly human-interpretable. These techniques learn a set of arguments as an intermediate representation. Arguments are small rules with exceptions that can be chained to larger arguments for...
Conference Paper
Full-text available
Human reasoning under uncertainty is conjectured to use Mental Models as a representation format. Each Mental Model characterizes a possible state of the world based on and constrained by the available information. Conclusion about the world must hold in each of these Mental Models. An important task in human reasoning is the construction these Men...
Conference Paper
Full-text available
Learning arguments is highly relevant to the field of explainable artificial intelligence. It is a family of symbolic machine learning techniques that is particularly human-interpretable. These techniques learn a set of arguments as an intermediate representation. Arguments are small rules with exceptions that can be chained to larger arguments for...
Chapter
Full-text available
A semantic tableau method, called an argumentation tableau, that enables the derivation of arguments, is proposed. First, the derivation of arguments for standard propositional and predicate logic is addressed. Next, an extension that enables reasoning with defeasible rules is presented. Finally, reasoning by cases using an argumentation tableau is...
Chapter
Full-text available
This paper proposes a new form of diagnosis and repair based on reinforcement learning. Self-interested agents learn locally which agents may provide a low quality of service for a task. The correctness of learned assessments of other agents is proved under conditions on exploration versus exploitation of the learned assessments.
Article
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This paper contributes to the literature on energy efficient gaits on unknown terrains for humanoid robots, the locomotion system of which has anthropomorphic characteristics. In this work, we firstly present an energy efficient gait for humanoid robots. The main feature of the new gait is the absence of an area of support. The stiffness-free foot...
Conference Paper
Full-text available
Motion segmentation for 2D videos is usually based on tracked 2D point motions, obtained for a sequence of frames. However, the 3D real world motion consistency is easily lost in the process, due to projection from 3D space to the 2D image plane. Several approaches have been proposed in the literature to recover 3D motion consistency from 2D point...
Chapter
Since its start in 1992, the bachelor’s programme Knowledge Engineering has had a strong focus on research and practical applications through its project-centred learning (PCL) approach. PCL has been a key factor for the programme’s high ranking over the last 20 years. The introduction of MaRBLe in the bachelor Data Science and Knowledge Engineerin...
Conference Paper
In the previous work we presented a new gait for humanoid robots, such as the Nao developed by Aldebaran. This new gait implemented on a Nao, reduces the energy consumption by 41 %. Then main feature of the new gait is the absence of an area of support. The foot can rotate freely around the ankle joint. This feature makes the gait suited for uneven...
Article
Full-text available
Ontology mapping is a crucial task for the facilitation of information exchange and data integration. A mapping system can use a variety of similarity measures to determine concept correspondences. This paper proposes the integration of word-sense disambiguation techniques into lexical similarity measures. We propose a disambiguation methodology wh...
Conference Paper
Full-text available
Matching ontologies which utilize significantly heterogeneous terminologies is a challenging task for existing matching techniques. These techniques typically exploit lexical resources in order to enrich the ontologies with additional terminology such that more terminological matches can be found. However, they are limited by the availability of an...
Conference Paper
Full-text available
Computing alignments between ontologies is a crucial task for the facilitation of information exchange between knowledge systems. An alignment is a mapping consisting of a set of correspondences, where each correspondence denotes two ontology concepts denoting the same information. In this domain, it can occur that a partial alignment is generated...
Conference Paper
Full-text available
The BDI architecture is one of the most popular archi-tectures 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...
Conference Paper
Full-text available
This paper presents a framework to generate energy efficient dynamic human-like walk for a Nao humanoid robot. We first extend the inverted pendulum model with the goal of finding an energy efficient and stable walking gait. In this model, we propose a leg control policy which utilizes joint stiffness control. We use policy gradient reinforcement l...
Article
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The semantic web is an open and distributed environment in which it is hard to guarantee consistency of knowledge and information. Under the standard two-valued semantics everything is entailed if knowledge and information is inconsistent. The semantics of the paraconsistent logic LP offers a solution. However, if the available knowledge and inform...
Article
Full-text available
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-...
Conference Paper
Full-text available
Ontology mapping is a crucial step for the facilitation of information exchange between knowledge sources. In the industry this process is of-ten performed semi-automatically, with a domain expert supervising the process. Such an expert can supply a partial alignment, known as an-chors, which can be exploited with more elaborate mapping techniques...
Conference Paper
Full-text available
Facilitating information exchange is a crucial service for ontology-based knowl-edge systems. This can be achieved by the mapping of two heterogenous on-tologies. Many mapping frameworks utilize language-based knowledge resources such as WordNet. By coupling all ontology concepts to a corresponding entry in WordNet, one can quantify the lexical rel...
Article
Paraconsistent logic is an attractive approach when dealing with a huge amount of knowledge in an open, dynamic and collaborative environment. It allows users to draw useful conclusions in the presence of inconsistencies. In this sense, introducing paraconsistent reasoning into standard reasoning system not only economizes resources used for fixing...
Conference Paper
Full-text available
This paper summarizes the results of the participation of MaasMatch in the Ontology Alignment Evaluation Initiative (OAEI) of 2012. We provide a brief description of the techniques that have been applied, with the emphasis being on the utilized similarity measures and the performed improvements over the system that participated in the year 2011. Ad...
Article
Full-text available
Matching ontologies is a crucial process when facilitating system interoperability and information exchange. A reoccurring problem in this process is that names can be ambiguous, yielding uncertainty to whether entities of two heterogeneous ontologies are actually related. Linguistic ontologies provide a clear structure of meanings, rather than nam...
Article
Full-text available
Although the preferential model semantics is the standard se- mantics for non-monotonic reasoning systems, it is not used for argumentation frameworks. For argumentation frame- works, instead, argumentation semantics are used. This paper studies the relation between the two types of semantics. Sev- eral argumentation semantics are related to additi...
Conference Paper
Full-text available
In constraint satisfaction, decomposition is a common technique to split a problem in a number of parts in such a way that the global solution can be efficiently assembled from the solutions of the parts. In this paper, we study the decomposition problem from an autonomous agent perspective. Here, a con- straint problem has to be solved by differen...
Article
Full-text available
We consider a model-based diagnosis approach to the diagnosis of plans. Here, a plan executed by some agent(s) is considered as a system to be di- agnosed. 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 observations...
Conference Paper
Full-text available
This paper addresses decentralized multi-project scheduling under uncertainty. The problem instance we study is the scheduling of airport ground handling services, where air- craft turnarounds can be seen as multiple projects, ground handling services as activities, and service providers as re- sources. In this environment aircraft requiring ground...
Article
Full-text available
Models used for Model-Based Diagnosis usually assume that the inaccuracy of data is smaller than the precision with which the data is described. In some domains, however, this assumption is invalid. Obser-vations may not be accurate or the behavior model of the system does not allow for accurate predictions. Therefore, the accuracy of predictions,...
Conference Paper
Full-text available
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. Most plans have to satisfy temporal constraints. An important and common occurring problem during plan execution are violations of temporal plan constraints. This paper addres...
Conference Paper
Full-text available
The most common reason for plan repair are the violation of a plan's temporal constraints. Air Traffic Control is an example of an area in which viola- tions of the plan's temporal constraints is rather a rule than an exception. In such domains there is a need for identifying the underlying causes of the constraint violations in order to improve pl...
Conference Paper
Full-text available
Failures in plan execution can be attributed to errors in the execution of plan steps or violations of the plan structure. The structure of a plan prescribes which actions have to be performed and which precedence con- straints between them have to be respected. Especially in multi-agent envi- ronments violations of plan structure might easily occu...
Conference Paper
Full-text available
In real-life multi-agent planning problems, long-term plans will often be invalidated by changes in the environment during or after the planning process. When this happens, short-term operational plan- ning and scheduling methods have to be applied in order to deal with these changed situations. In addition to the dynamic environment, in such plann...
Conference Paper
Full-text available
Failures in plan execution can be attributed to errors in the execution of plan steps or violations of 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 environ- ments violations of plan structure might easily occur...
Conference Paper
Full-text available
Many multi-agent systems are intended to operate together with or as a service to humans. Typically, multi-agent systems are designed assuming perfectly rational, self-interested agents, according to the principles of classical game theory. However, research in the field of behavioral economics shows that humans are not purely self-interested; they...
Article
Full-text available
The most common reason for plan repair are the violation of a plan's temporal constraints. Air Traffic Control is an example of an area in which violations of the plan's temporal constraints is rather a rule than an exception. In such domains there is a need for identifying the underlying causes of the constraint vio-lations in order to improve pla...
Article
Full-text available
Results from disaster research suggest that methods for coordination between individual emergency responders and organizations should recognize the independence and autonomy of these actors. These actor features are key factors in effective adaptation and improvisation of response to emergency situations which are inherently uncertain. Autonomy and...
Data
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Article
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This paper investigates the combination of expert critiquing systems and formal medical protocols. Medical protocols might serve as a suitable basis for an expert critiquing system because of the ongoing acceptance of medical protocols and the rise of both evidence-based practice and evidence-based protocols. A prerequisite for a critiquing system...
Conference Paper
Full-text available
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) it provides information necessary for the adjustment of the current plan or for the development of a new plan, (ii) it can be used to point out which equipment and/or agents should be...
Article
Full-text available
The planning and scheduling of the deicing and anti-icing activities is an important and challenging part of airport departure planning. Deicing planning has to be done in a highly dynamic environment involving several autonomous and self-interested parties. Traditional centralized scheduling approaches do not ac-knowledge the autonomy of parties i...
Article
Full-text available
Expert critiquing systems were introduced to assist physicians in decision making, without forcing them to comply to a gold standard of care. Critiquing systems do this by providing critique on a physician's decisions, rather than telling him/her exactly what to do. In order to perform this task, a critiquing system must have knowledge of the diagn...
Conference Paper
Full-text available
Unexpected events during the execution of a plan may lead to conflicts: we then say that the plan execution is unhealthy. This paper presents a new model that enables agents (1) to control plan-execution health and (2) to regain health when necessary. The agents can utilize the model to predict consequences of occurring disruptions and thus detect...
Conference Paper
Full-text available
We discuss the application of Model-Based Diagnosis in (agent- based) planning. Here, a plan together with its executing agent is considered as a system to be diagnosed. It is assumed that the execution of a plan can be moni- tored by making partial observations of the results of actions. These observations are used to explain the observed deviatio...
Conference Paper
Full-text available
We discuss the application of Model-Based Diagnosis in (agent-based) planning. Here, a plan together with its executing agent is considered as a system to be diagnosed. It is assumed that the execution of a plan can be monitored by making partial observations of the results of actions. These observations are used to explain the observed deviations...
Conference Paper
Resource management problems are problems in which the goal is to optimize the utilization of resources over time. Dependencies between resources make it necessary to plan the proper utilization of these resources. Such a planning must often be constructed in an environment that is non-deterministic, for example due to competing agents. Traditional...
Conference Paper
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We propose a new framework to study problem solving in a computational society. Such a society consists of computational agents able to use information about the direct and indirect computational experiences of other agents. Our history-based computing framework generalizes existing computational frameworks that might be used in a computational age...
Conference Paper
Full-text available
We present a novel approach to multiagent planning for self-interested agents. The main idea behind our approach is that multiagent planning systems should be built upon (single-agent) plan repair systems. In our system agents can exchange goals and subgoals through an auction, using their own (planning) heuristics and utility functions to determin...
Article
Full-text available
We discuss the application of Model Based Diagnosis in agent-based planning. We model a plan as a system to be diagnosed and assume that agents can monitor the execution of the plan by making partial observations during plan execution. These observations are used by the agents to explain plan deviations (errors) by qualifying some action instances...
Article
Full-text available
This paper examines the principles that de- fine resource management games, popular and challenging constructive computer games such as SIMCITY and VIRTUAL U. From these principles, it is possible to derive requirements for intelligent programs designed to play such games, as a replacement of a human player. A first step for research in the domain...
Article
Full-text available
We discuss the application of model based diagnosis to (multi-) agent based planning. First, we model a plan as a system to be diagnosed, taking into account the behavioural relations that might exist between several instances of actions occurring in a plan. Then we consider the case of a spatially distributed agent planning system where different...
Article
Full-text available
This paper proposes a domain independent method for handling interoperability problems by learning a mapping between ontologies. The learning method is based on exchanging instances of concepts that are defined in the ontologies. The method starts with identifying pairs of instances of concepts denoting the same entity in the world using informatio...
Article
Full-text available
We consider the problem of finding a commonly agreed upon diagnosis for errors observed in a system monitored by a number of different expert agents. Each agent is assumed to have its own specialized (expert) view on the system and collectively, the agents have to agree on one or more diagnoses based on their views. Reaching an agreement is complic...
Conference Paper
Full-text available
This paper proposes a domain independent method for handling interoperability problems by learning a mapping between ontologies. The learning method is based on exchanging instances of concepts that are defined in the ontologies. The method starts with identifying pairs of instances of concepts denoting the same entity in the world using informatio...
Article
Full-text available
This paper presents an algorithm for plan health repair in multi-agent plan exe- cution. Plan-execution health repair aims at avoiding conflicts that might arise due to disruptions in the execution of a plan. This can be achieved by adjusting the execu- tions of tasks instead of replanning the tasks. For this purpose, established methods from the d...
Conference Paper
Full-text available
In a large distributed system it is often infeasible or even impossible to perform diagnosis using a single model of the whole system. Instead, several spatially distributed local models of the system have to be used to detect possible faults. Traditional diagnostic tools, however, are not suitable to deal with such a set of spatially distributed l...
Article
Full-text available
The paper introduces a knowledge-based multimedia approach to multimedia information retrieval. The approach uses domain knowledge to augment a user' s query, performs automatic ontology mapping to search different multimedia databases, and combines the results in a multimedia presentation. The texts in the presentation are generated from the domai...
Article
Full-text available
This paper analyzes the use of a Multi-Agent System for Model-Based Diagnosis. In a large dynamical system, it is often infeasible or even impossible to maintain a model of the whole system. Instead, several incomplete models of the system have to be used to establish a diagnosis and to detect possible faults. These models may also be physically di...
Conference Paper
Full-text available
The paper describes a peer-to-peer distributed-computing platform, called yaca, based on mobile agents. Next to the client agents, which seek computational resources in a cluster, yaca consists of four agents, who manage the computers within a cluster. (1) The Directory Agent keeps track of the computers belonging to the cluster. These computers ar...
Article
Full-text available
The paper describes a peer-to-peer distributed-computing platform, called YACA, based on mobile agents. Next to the client agents, which seek computational resources in a cluster, YACA consists of four agents, who manage the computers within a cluster. (1) The Directory Agent keeps track of the computers belonging to the cluster. These computers ar...
Conference Paper
Full-text available
Agent communication languages provide a standard for agent communication. For the protocol and the language used in the communication, several standards are available. This is not the case for the ontology used in the communication. The ontology depends on the subject of the communication. Since the number of subjects is almost infinite and since t...
Article
Full-text available
An important practical problem in schedule execution is the occurrence of unfore- seen events. Whether we consider a schedule for a Job Shop or a timetable for a school, an unexpected event, such as machine breakdowns or personnel illness, that disrupt the execution of the schedule will almost certainly occur once in a while. Hence, it be- comes im...
Article
Full-text available
Agent communication languages such as ACL and KQML provide a standard for agent communication. These languages enable an agent to specify the intention and the content of a message as well as the protocol, the language, and the ontology that are used. For the protocol and the language some standards are available and should be known by the communic...
Article
Full-text available
The paper analyzes the use of a Multi Agent System for Model Based Diagnosis. In a large dynamical system, it is often infeasible or even impossible to maintain a model of the whole system. Instead, several incomplete models of the system have to be used to detect possible faults. These models may also be physically be distributed. A Multi Agent Sy...
Conference Paper
Full-text available
Many hard practical problems such as Time Tabling and Scheduling can be formulated as Constraint Satisfaction Problems. For these CSPs, powerful problem-solving methods are available. However, in practice, the problem definition may change over time. Each separate change may invoke a new CSP formulation. The resulting sequence of CSPs is denoted as...
Article
Full-text available
Argument systems are based on the idea that one can construct arguments for propositions; i.e., structured reasons justifying the belief in a proposition. Using defeasible rules, arguments need not be valid in all circumstances, therefore, it might be possible to construct an argument for a proposition as well as its negation. When rguments support...
Article
Full-text available
. Several attempts have been made to give an objective definition of subjective probability. These attempts can be divided into two approaches. The first approach uses an a priori probability distribution over the set of interpretations of the language that we are using to describe information. The idea is to define such an a priori probability dis...
Article
Full-text available
In this paper, an efficient model-based diagnostic process is described for systems whose components possess a causal relation between their inputs and their outputs. In this diagnostic process, a set of focuses on likely broken components is first determined. Secondly, for each focus, the most informative probing point within the focus can be dete...
Conference Paper
In this paper a reasoning process is viewed as a process of constructing a partial model of the world we are reasoning about. This partial model is a syntactic representation of an epistemic partial semantic model. In such a partial model different views on the world we are reasoning about can be represented. Multiple views can be the result of upd...
Article
Full-text available
Developing a conflict-free plan for a multi-agent system in a complex and dynamic environment is a difficult task. Moreover, it is impossible to take into account all possible events that might occur dur-ing the execution of the plan. Unexpected events may cause a plan to be no longer executable with-out leading to conflicts: we then say that its e...
Article
Full-text available
This paper investigates the combination of expert cri-tiquing systems and formal medical guidelines. Medical guidelines might serve as a suitable basis for an expert critiquing system because of the ongoing acceptance of medical guidelines and the rise of both evidence-based practice and evidence-based guidelines. A prerequi-site for a critiquing s...