Ontology-Based Interactive Information Extraction From Scientific Abstracts

Over recent years, there has been a growing interest in extracting information automatically or semi-automatically from the scientific literature. This paper describes a novel ontology-based interactive information extraction (OBIIE) framework and a specific OBIIE system. We describe how this system enables life scientists to make ad hoc queries similar to using a standard search engine, but where the results are obtained in a database format similar to a pre-programmed information extraction engine. We present a case study in which the system was evaluated for extracting co-factors from EMBASE and MEDLINE

Recovering from Modeling Faults in GOLOG

In this paper we study the problem of detection, classification and recovery from discrepancies due to faulty modeling of controlled systems. We do this by extending the existing Execution Monitoring mechanism for the high-level robot programming language GOLOG [ De Giacomo et al., 1998 ] by introducing a revision technique that transforms the faulty underlying situation calculus theory to a theory that reflects the controlled system more adequately. 1 Introduction Execution Monitoring (EM) has been widely studied by AI researchers (see e.g. [ Ambros-Ingerson and Steel, 1988; Knoblock, 1995; Simmons et al., 1997; Doyle et al., 1986; Beetz and McDermott, 1994 ] ) and can be defined as an agent's process of identifying discrepancies between observations of the actual world and the prediction and expectations derived from its representation of the world, classifying such discrepancies, and recover from them. While most of the previous work on EM has focused on monitoring of plan execut..

Execution Monitor Synthesis for Hybrid Systems

Formal verification methods for hybrid controllers have received a lot of attention during the last decade and so has the problem of synthesizing specifications of hybrid controllers. Such specifications do then fulfill given requirements, such as timing constraints or safety properties. However, the problem of automatically implementing the actual control programs has received much less attention, and one of the reasons for this is that industrial controllers necessarily have to be able to effectively handle every conceivable situation that might occur in reality, which make the construction of the specification very difficult. In this preliminary report, we take one step towards automatic generation of control systems by proposing that not only the control program should be synthesized from a specification, but also an Execution Monitor that is able to detect and classify discrepancies between the model of the closed-loop system and the actual effects of control actions. We show how..

Exploiting Bipartiteness to Identify Yet Another Tractable Subclass of CSP

The class of constraint satisfaction problems (CSPs) over finite domains has been shown to be NP-complete, but many tractable subclasses have been identified in the literature. In this paper we are interested in restrictions on the types of constraint relations in CSP instances. By a result of Jeavons et al. we know that a key to the complexity of classes arising from such restrictions is the closure properties of the sets of relations. It has been shown that sets of relations that are closed under constant, majority, affine, or associative, commutative, and idempotent (ACI) functions yield tractable subclasses of CSP. However, it has been unknown whether other closure properties may generate tractable subclasses. In this paper we introduce a class of tractable (in fact, SL-complete) CSPs based on bipartite graphs. We show that there are members of this class that are not closed under constant, majority, affine, or ACI functions, and that it, therefore, is incomparable with..

Ontological Control

Execution monitoring has been defined as an agent's process of observing the world for discrepancies between the actual world and its internal representation, and recovering from such discrepancies. Although there exists a body of research in this area, few researchers have taken interest in classifications of the discrepancies, especially the distinction between discrepancies due to unobservable uncontrollable actions, and discrepancies due to the fact that the representation does not reflect the world in an adequate way. In Ontological Control we are interested in object-level execution systems, i.e. control systems that are in immediate contact with the world via sensors and actuators. In sufficiently complex control situations there are always a number of unmodelled assumptions, which necessarily must hold for the control system to be valid. In this paper we show how violations of such ontological assumptions can be correctly classified in a PLC setting, and we define a recovery pr..

Reasoning about Action in Polynomial Time

Although many formalisms for reasoning about action exist, surprisingly few approaches have taken computational complexity into consideration. The contributions of this paper are the following: a temporal logic with a restriction for which deciding satisfiability is tractable, a tractable extension for reasoning about action, and NP-completeness results for the unrestricted problems. Many interesting reasoning problems can be modelled, involving nondeterminism, concurrency and memory of actions. The reasoning process is proved to be sound and complete. 145 1 Introduction Although many formalisms for reasoning about action exist, surprisingly few approaches have taken computational complexity into consideration. One explanation for this might be that many interesting AI problems are (at least) NP-hard, and that tractable subproblems that are easily extracted, tend to lack expressiveness. This has led a large part of the AI community to rely on heuristics and incomplete systems to s..

Reasoning by Regression: Pre- and Postdiction Procedures for Logics of Action and Change with Nondeterminism

In this paper we introduce regression-based pre- and postdiction procedures for PMON, a nonmonotonic logic for action and change with explicit time. We also provide an in depth analysis of problems with regression that occur when nondeterministic actions are introduced. We do this by employing Dijkstra's weakest liberal precondition operator, wlp. The presented work is related to recent work by Lin in situation calculus, and we identify and deal with three problems with his approach. Our conjecture is that our approach can be mapped back to situation calculus. 1 Introduction The contributions of this paper are the following: Regression-based pre- and postdiction procedures for PMON with metric time, and an in depth analysis of problems with regression that occur when nondeterministic actions are introduced. We also identify and deal with problems in previous work by Lin [ 1996 ] . Lin [ 1996 ] proposes a causal minimization framework in SitCalc (Situation Calculus), where effects of ..

Synthesizing Discrete Controllers from Hybrid Automata

The task of synthesizing and verifying a specification of a controller for a hybrid system is different from the task of synthesizing an executable controller. Specifications of controllers are very useful for the verification of the closedloop system, but the verification procedure often requires that the system behaves in an ideal way. In, e.g., automata approaches, it is typically required that the initial state is known, and that the actual system under control behaves according to its model. In industrial applications such requirements are unrealistic; an industrial controller can never make assumptions about the initial state, and it must be able to handle desynchronizations, i.e. deviations from the expected effects of control actions. In this paper we present preliminary results on how to synthesize robust discrete controllers from a class of Rectangular Hybrid Automata. The language used for the synthesized controllers is Nils Nilsson's Teleo-Reactive Trees. We prove that the ..