Automated Analysis of Compositional Multi-Agent Systems

Abstract. An approach for handling the complex dynamics of a multi-agent system is based on distinguishing aggregation levels. The behaviour at a given aggregation level is specified by a set of dynamic properties at that level, expressed in some (temporal) language. Such behavioural specifications may be complex and difficult to analyse. To enable automated analysis of system specifications, a simpler format is required. To this end, a specification at a lower aggregation level can be created, describing basic steps in the processes of a system. This paper presents a method and tool to support the automated creation of such a specification, as a refinement of a given higher level specification. The generated specification has a simple format which can easily be used for analysis. This paper describes an approach for automated verification of logical consequences of specifications using model checking techniques

Automatic Sequences and Zip-Specifications

We consider infinite sequences of symbols, also known as streams, and the decidability question for equality of streams defined in a restricted format. This restricted format consists of prefixing a symbol at the head of a stream, of the stream function `zip', and recursion variables. Here `zip' interleaves the elements of two streams in alternating order, starting with the first stream. For example, the Thue-Morse sequence is obtained by the `zip-specification' {M = 0 : X, X = 1 : zip(X,Y), Y = 0 : zip(Y,X)}. Our analysis of such systems employs both term rewriting and coalgebraic techniques. We establish decidability for these zip-specifications, employing bisimilarity of observation graphs based on a suitably chosen cobasis. The importance of zip-specifications resides in their intimate connection with automatic sequences. We establish a new and simple characterization of automatic sequences. Thus we obtain for the binary zip that a stream is 2-automatic iff its observation graph using the cobasis (hd,even,odd) is finite. The generalization to zip-k specifications and their relation to k-automaticity is straightforward. In fact, zip-specifications can be perceived as a term rewriting syntax for automatic sequences. Our study of zip-specifications is placed in an even wider perspective by employing the observation graphs in a dynamic logic setting, leading to an alternative characterization of automatic sequences. We further obtain a natural extension of the class of automatic sequences, obtained by `zip-mix' specifications that use zips of different arities in one specification. We also show that equivalence is undecidable for a simple extension of the zip-mix format with projections like even and odd. However, it remains open whether zip-mix specifications have a decidable equivalence problem

A generic multibody simulation

Described is a dynamic simulation package which can be configured for orbital test scenarios involving multiple bodies. The rotational and translational state integration methods are selectable for each individual body and may be changed during a run if necessary. Characteristics of the bodies are determined by assigning components consisting of mass properties, forces, and moments, which are the outputs of user-defined environmental models. Generic model implementation is facilitated by a transformation processor which performs coordinate frame inversions. Transformations are defined in the initialization file as part of the simulation configuration. The simulation package includes an initialization processor, which consists of a command line preprocessor, a general purpose grammar, and a syntax scanner. These permit specifications of the bodies, their interrelationships, and their initial states in a format that is not dependent on a particular test scenario

A scene model of exosolar systems for use in planetary detection and characterisation simulations

Instrumental projects that will improve the direct optical finding and characterisation of exoplanets have advanced sufficiently to trigger organized investigation and development of corresponding signal processing algorithms. The first step is the availability of field-of-view (FOV) models. These can then be submitted to various instrumental models, which in turn produce simulated data, enabling the testing of processing algorithms. We aim to set the specifications of a physical model for typical FOVs of these instruments. The dynamic in resolution and flux between the various sources present in such a FOV imposes a multiscale, independent layer approach. From review of current literature and through extrapolations from currently available data and models, we derive the features of each source-type in the field of view likely to pass the instrumental filter at exo-Earth level. Stellar limb darkening is shown to cause bias in leakage calibration if unaccounted for. Occurrence of perturbing background stars or galaxies in the typical FOV is unlikely. We extract galactic interstellar medium background emissions for current target lists. Galactic background can be considered uniform over the FOV, and it should show no significant drift with parallax. Our model specifications have been embedded into a Java simulator, soon to be made open-source. We have also designed an associated FITS input/output format standard that we present here.Comment: 9 pages (+5 of appendices), 7 figures, accepted for publication in Astronomy & Astrophysic

Providing Meteorological and Hydrographic Information via AIS Application-Specific Messages: Challenges and Opportunities

AIS Application-Specific Messages (ASMs) transmitted in binary format will be increasingly used to digitally communicate maritime safety/security information between participating vessels and shore stations. This includes time-sensitive metrological and hydrographic (met/hydro) information that is critical for safe vessel transits and efficient ports/waterways management. IMO recently published a new Safety-of-Navigation Circular (SN.1./Circ.289) that includes a number of meteorological and hydrographic message applications and data parameters. While there are no specific display standards for AIS ASMs on shipborne or shore-based systems, IMO Has also issued general guidance for the presentation/display of ASMs (SN.1/Circ.290). It includes specific mention of conforming to the e-Navigation concept-of-operation. For any new IHO S-57 or S-100-related product specifications dealing with dynamic met/hydro information, IHO and its Member States should use the same data content fields and parameters that are defined in IMO SN.1/Circ.289. Also, there is a need to consider the implications of IMO guidance regarding the presentation/display of AIS ASMs on ECDIS

An overview of the ciao multiparadigm language and program development environment and its design philosophy

We describe some of the novel aspects and motivations behind the design and implementation of the Ciao multiparadigm programming system. An important aspect of Ciao is that it provides the programmer with a large number of useful features from different programming paradigms and styles, and that the use of each of these features can be turned on and off at will for each program module. Thus, a given module may be using e.g. higher order functions and constraints, while another module may be using objects, predicates, and concurrency. Furthermore, the language is designed to be extensible in a simple and modular way. Another important aspect of Ciao is its programming environment, which provides a powerful preprocessor (with an associated assertion language) capable of statically finding non-trivial bugs, verifying that programs comply with specifications, and performing many types of program optimizations. Such optimizations produce code that is highly competitive with other dynamic languages or, when the highest levéis of optimization are used, even that of static languages, all while retaining the interactive development environment of a dynamic language. The environment also includes a powerful auto-documenter. The paper provides an informal overview of the language and program development environment. It aims at illustrating the design philosophy rather than at being exhaustive, which would be impossible in the format of a paper, pointing instead to the existing literature on the system

S-100 Overlays: A Brave New World?

Marine Information Overlay (MIO) is a generic term used to describe chart and navigation related information that supplement the content that is already contained in an ENC. This includes both static and dynamic information such as tide/water level, current flow, meteorological, oceanographic, and environmental protection. With the advent of S-100 and S-101, there is increased interest in providing a wide variety of ‘new’ overlay information. This paper provides a brief history of S-57 MIOs. Examples of navigational and non-navigation MIOs are given in terms of how currently used, by who, and for what purpose. Recommendations are provided for making a transition from S-57 MIOs to S-100 overlays that can be used with the ‘Next Generation’ ENC. More specifically, what has been proposed, how should they work, who will provide, and some future challenges/opportunities related to implementation

Integration of CasADi and JModelica.org

This paper presents the integration of two open source softwares: CasADi, which is a framework for efficient evaluation of expressions and their derivatives, and the Modelica-based platform JModelica.org. The integration of the tools is based on an XML format for exchange of DAE models. The JModelica.org platform supports export of model in this XML format, whereas CasADi supports import of models expressed in this format. Furthermore, we have carried out comparisons with ACADO, which is a multiple shooting package for solving optimal control problems. CasADi, in turn, has been interfaced with ACADO Toolkit, enabling users to define optimal control problems using Modelica and Optimica specifications, and use solve using direct multiple shooting. In addition, a collocation algorithm targeted at solving large- scale DAE constrained dynamic optimization problems has been implemented. This implementation explores CasADi’s Python and IPOPT interfaces, which offers a convenient, yet highly efficient environment for development of optimization algorithms. The algorithms are evaluated using industrially relevant benchmark problems

Combinatorial synthesis of oxysulfides in the lanthanum-bismuth-copper system

Establishing synthesis methods for a target material constitutes a grand challenge in materials research, which is compounded with use-inspired specifications on the format of the material. Solar photochemistry using thin film materials is a promising technology for which many complex materials are being proposed, and the present work describes application of combinatorial methods to explore the synthesis of predicted La–Bi–Cu oxysulfide photocathodes, in particular alloys of LaCuOS and BiCuOS. The variation in concentration of three cations and two anions in thin film materials, and crystallization thereof, is achieved by a combination of reactive sputtering and thermal processes including reactive annealing and rapid thermal processing. Composition and structural characterization establish composition-processing-structure relationships that highlight the breadth of processing conditions required for synthesis of LaCuOS and BiCuOS. The relative irreducibility of La oxides and limited diffusion indicate the need for high temperature processing, which conflicts with the temperature limits for mitigating evaporation of Bi and S. Collectively the results indicate that alloys of these phases will require reactive annealing protocols that are uniquely tailored to each composition, motivating advancement of dynamic processing capabilities to further automate discovery of synthesis routes