Abstract: The provision of advanced location-based services in indoor environments is based on the possibility of estimating the positions of mobile devices with sufficient accuracy and robustness. An algorithm to allow a software agent hosted on a mobile device to estimate the position of its device in a known indoor environment is proposed under the ordinary assumption that fixed beacons are installed in the environment at known locations. Rather than making use of geometric considerations to estimate the position of the device, the proposed algorithm first transforms the localization problem into a related optimization problem, which is then solved by means…of interval arithmetic to provide the agent with accurate and robust position estimates. The adopted approach solves a major problem that severely limits the accuracy of the position estimates that ordinary geometric algorithms provide when the beacons are positioned to maximize line-of-sight coverage. Experimental results confirm that the proposed algorithm provides position estimates that are independent of the positions of the beacons, and they show that the algorithm outperforms a well-known geometric algorithm.
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Keywords: Localization as optimization, indoor localization, software agents
Abstract: This paper introduces an instantiation of the constraint logic programming scheme called CLP(PolyFD) in which variables take values from finite subsets of the integers and constraints are expressed as equalities, inequalities, and disequalities of polynomials with integer coefficients. Such constraints, which we call polynomial constraints over finite domains, can be treated effectively by means of a specific solver under the assumption that initial approximations of the domains of variables are available. The proposed solver deals with constraints in a canonical form and it uses the modified Bernstein form of polynomials to detect the satisfiability of constraints. The solver is complete…and a preliminary assessment of its performance is reported.
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Abstract: Software agents are normally expected to operate in open and dynamic environments, and therefore they are often supposed to face situations that significantly deviate from the nominal course of events. The effective management of exceptional situations is of paramount importance to provide agents with the needed means to operate in their environments, mostly because these situations should be considered as the norm in open and dynamic environments. This paper presents some recent additions to the Jadescript agent-oriented programming language that were specifically designed to provide agents with the needed capabilities to effectively detect and manage exceptional situations. The first part…of this paper motivates the need of sophisticated exception handling capabilities, also by relating the proposed language features with the state of the art documented in the literature. Then, the second part of this paper discusses the proposed language features, also considering the conceptual similarities and differences with the related features normally available in mainstream programming languages. In particular, the proposed language features are presented in terms of three language improvements: the general-purpose support to handle exceptions, the specific support to handle behaviour failures, and the specific support to handle stale messages. Finally, before concluding with some indications on future research activities, the third part of this paper describes a concrete example intended to practically present the actual use of the new language features.
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