Mapping Fusion and Synchronized Hyperedge Replacement into Logic Programming

In this paper we compare three different formalisms that can be used in the area of models for distributed, concurrent and mobile systems. In particular we analyze the relationships between a process calculus, the Fusion Calculus, graph transformations in the Synchronized Hyperedge Replacement with Hoare synchronization (HSHR) approach and logic programming. We present a translation from Fusion Calculus into HSHR (whereas Fusion Calculus uses Milner synchronization) and prove a correspondence between the reduction semantics of Fusion Calculus and HSHR transitions. We also present a mapping from HSHR into a transactional version of logic programming and prove that there is a full correspondence between the two formalisms. The resulting mapping from Fusion Calculus to logic programming is interesting since it shows the tight analogies between the two formalisms, in particular for handling name generation and mobility. The intermediate step in terms of HSHR is convenient since graph transformations allow for multiple, remote synchronizations, as required by Fusion Calculus semantics.Comment: 44 pages, 8 figures, to appear in a special issue of Theory and Practice of Logic Programming, minor revisio

Primitives for Contract-based Synchronization

We investigate how contracts can be used to regulate the interaction between processes. To do that, we study a variant of the concurrent constraints calculus presented in [1], featuring primitives for multi-party synchronization via contracts. We proceed in two directions. First, we exploit our primitives to model some contract-based interactions. Then, we discuss how several models for concurrency can be expressed through our primitives. In particular, we encode the pi-calculus and graph rewriting.Comment: In Proceedings ICE 2010, arXiv:1010.530

05081 Abstracts Collection -- Foundations of Global Computing

From 20.02.05 to 25.02.05, the Dagstuhl Seminar 05081 on ``Foundations of Global Computing\u27\u27 was held in the International Conference and Research Center (IBFI), Schloss Dagstuhl. During the seminar, several participants presented their current research, and ongoing work and open problems were discussed. Abstracts of the presentations given during the seminar as well as abstracts of seminar results and ideas are put together in this paper. The first section describes the seminar topics and goals in general. Links to extended abstracts or full papers are provided, if available

04241 Abstracts Collection -- Graph Transformations and Process Algebras for Modeling Distributed and Mobile Systems

Recently there has been a lot of research, combining concepts of process algebra with those of the theory of graph grammars and graph transformation systems. Both can be viewed as general frameworks in which one can specify and reason about concurrent and distributed systems. There are many areas where both theories overlap and this reaches much further than just using graphs to give a graphic representation to processes. Processes in a communication network can be seen in two different ways: as terms in an algebraic theory, emphasizing their behaviour and their interaction with the environment, and as nodes (or edges) in a graph, emphasizing their topology and their connectedness. Especially topology, mobility and dynamic reconfigurations at runtime can be modelled in a very intuitive way using graph transformation. On the other hand the definition and proof of behavioural equivalences is often easier in the process algebra setting. Also standard techniques of algebraic semantics for universal constructions, refinement and compositionality can take better advantage of the process algebra representation. An important example where the combined theory is more convenient than both alternatives is for defining the concurrent (noninterleaving), abstract semantics of distributed systems. Here graph transformations lack abstraction and process algebras lack expressiveness. Another important example is the work on bigraphical reactive systems with the aim of deriving a labelled transitions system from an unlabelled reactive system such that the resulting bisimilarity is a congruence. Here, graphs seem to be a convenient framework, in which this theory can be stated and developed. So, although it is the central aim of both frameworks to model and reason about concurrent systems, the semantics of processes can have a very different flavour in these theories. Research in this area aims at combining the advantages of both frameworks and translating concepts of one theory into the other. The Dagsuthl Seminar, which took place from 06.06. to 11.06.2004, was aimed at bringing together researchers of the two communities in order to share their ideas and develop new concepts. These proceedings4 of the do not only contain abstracts of the talks given at the seminar, but also summaries of topics of central interest. We would like to thank all participants of the seminar for coming and sharing their ideas and everybody who has contributed to the proceedings

A logic for application level QoS

Service Oriented Computing (SOC) has been proposed as a paradigm to describe computations of applications on wide area distributed systems. Awareness of Quality of Service (QoS) is emerging as a new exigency in both design and implementation of SOC applications. We do not refer to QoS aspects related to low-level performance and focus on those high-level non-functional features perceived by end-users as application dependent requirements, e.g., the price of a given service, or the payment mode, or else the availability of a resource (e.g., a file in a given format). In this paper we present a logic which includes mechanisms to consider the three main dimensions of systems, namely their structure, behaviour and QoS aspects. The evaluation of a formula is a value of a constraint-semiring and not just a boolean value expressing whether or not the formula holds. This permits to express not only topological and temporal properties but also QoS properties of systems. The logic is interpreted on SHReQ, a formal framework for specifying systems that handles abstract high-level QoS aspects combining Synchronised Hyperedge Replacement with constraint-semirings

Formal aspects of a service oriented execution model

El software distribuido que resulta de los nuevos paradigmas que están emergiendo, tales como el de computación orientada a servicios (SOC), computación en la nube e internet de las cosas, está transformando el mundo de los sistemas de software de modo de dar soporte a aplicaciones capaces de responder y adaptarse a los cambios en su entorno de ejecución, dando impulso a lo que se conoce como la economía de las APIs. La idea que subyace a la economía de las APIs es que es posible construir piezas de software a partir de componer servicios previamente registrados en repositorios y provistos por terceros. Esto promete una generación de aplicaciones ejecutando sobre recursos computacionales y una infraestructura de comunicación globalmente distribuidos que, en tiempo de ejecución son reconfiguradas dinámica y transparentemente mediante la intervención de un middleware dedicado. Esta reconfiguración está sujeta a la negociación de un acuerdo de nivel de servicio - SLA [25]. En este paradigma los servicios de software son accedidos a través de sus APIs. Muchos de los aspectos relacionados con la provisión de fundamentos formales y herramientas para dar soporte a estos nuevos paradigmos han sido resueltos en los últimos años [66], sin embargo algunos permanecen abiertos. En particular la habilidad para proveer una infraestructura capaz de llevar a cabo los procesos de discovery y bindig de manera completamente automática es aún un desafío abierto [33, 59]. En esta tesis contribuimos a este objetivo haciendo foco en dos aspectos del problema: (1) la provisión de elementos formales capaces de capturar las particularidades de estos paradigmas siendo la más relevante el hecho de que no es posible saber en tiempo de diseño qué servicio, si es que alguno, podrá satisfacer un determinado requerimiento y (2) la necesidad de ser capaces de determinar en tiempo de ejecución si existe un servicio particular, en un repositorio dado, capaz de satisfacer un determinado requerimiento. Como contribución al punto (1) proporcionamos una semántica operacional para las Asynchronous Relational Networks [24] que captura tanto las transiciones internas como las acciones de reconfiguración que ocurren durante la ejecución de un servicio. También extendimos esta semántica con la habilidad para capturar reconfiguraciones no incrementales con respecto a la estructura, de modo de dar soporte a la falta de confiabilidad derivada de la infraestructura de ejecución. Como contribución al punto (2) exploramos el uso de CFSMs [9] en nuestro modelo para expresar tanto requerimientos como contratos de provisión de servicio. De esta manera recurrimos al mecanismo dado en [38] para proveer un chequedo de interoperabilidad automático para servicios. También extendimos las CFSMs y las equipamos con datos y condiciones de tipo asunción/garantía en la forma de fórmulas de primer orden sobre esos datos. De este modo transformamos a las CFSMs en un mecanismo apropiado para expresar y chequear contratos funcionales restringidos.Distributed software resulting from emerging paradigms such as serviceoriented computing (SOC), Cloud/Fog computing and the Internet of Things are transforming the world of software systems in order to support applications able to respond and adapt to the changes of their execution environment, giving impulse to what is called the API’s economy. The underlying idea of the API’s economy is that it is possible to construct software artifacts, usually by composing services previously registered in repositories and provided by third parties. This envisages a generation of applications running over globally available computational resources and communication infrastructure, which, at run-time, are dynamically and transparently reconfigured by the intervention of a dedicated middleware, subject to the negotiation of a Service Level Agreement – SLA [25]. Under this paradigm software services are accessed by their API. Many of the aspects related to providing formal foundations and tool support for these new paradigms have been tackled in the last years [66], yet some remain open. In particular the ability to provide a working infrastructure capable of realizing full automatic service discovery and binding is still an open challenge [33, 59]. In this thesis we contribute to this goal by focusing on two facets of the problem: (1) the provision of a formal setting capable of capturing the particularities of these paradigms, being the most relevant the fact that one cannot know at design time which service (if some) will satisfy a requirement and (2) the necessity of being capable of determining at runtime whether there exists a service, in a given repository, capable of satisfying a given requirement. As contribution to aspect (1) we provide an operational semantics for Asynchronous Relational Networks [24] that takes into account both internal and reconfiguration actions. We also extend this semantics with the ability to capture reconfigurations that are not incremental on the structure in order to support unreliability derived from the execution infrastructure. As contribution to aspect (2) we explore the usage of CFSMs [9] in our model to express both requirements and provision contracts. In this way we resort to the mechanism given in [38] to provide an automatic interoperability check for services. We also extended CFSMs in order to equip them with data and assume/guarantee conditions in the form of first order formulae over this data. In this way we transform CFSMs in a suitable mechanism for expressing and checking (restricted) functional contracts.Fil: Vissani, Ignacio. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Occlusion reasoning for multiple object visual tracking

Thesis (Ph.D.)--Boston UniversityOcclusion reasoning for visual object tracking in uncontrolled environments is a challenging problem. It becomes significantly more difficult when dense groups of indistinguishable objects are present in the scene that cause frequent inter-object interactions and occlusions. We present several practical solutions that tackle the inter-object occlusions for video surveillance applications. In particular, this thesis proposes three methods. First, we propose "reconstruction-tracking," an online multi-camera spatial-temporal data association method for tracking large groups of objects imaged with low resolution. As a variant of the well-known Multiple-Hypothesis-Tracker, our approach localizes the positions of objects in 3D space with possibly occluded observations from multiple camera views and performs temporal data association in 3D. Second, we develop "track linking," a class of offline batch processing algorithms for long-term occlusions, where the decision has to be made based on the observations from the entire tracking sequence. We construct a graph representation to characterize occlusion events and propose an efficient graph-based/combinatorial algorithm to resolve occlusions. Third, we propose a novel Bayesian framework where detection and data association are combined into a single module and solved jointly. Almost all traditional tracking systems address the detection and data association tasks separately in sequential order. Such a design implies that the output of the detector has to be reliable in order to make the data association work. Our framework takes advantage of the often complementary nature of the two subproblems, which not only avoids the error propagation issue from which traditional "detection-tracking approaches" suffer but also eschews common heuristics such as "nonmaximum suppression" of hypotheses by modeling the likelihood of the entire image. The thesis describes a substantial number of experiments, involving challenging, notably distinct simulated and real data, including infrared and visible-light data sets recorded ourselves or taken from data sets publicly available. In these videos, the number of objects ranges from a dozen to a hundred per frame in both monocular and multiple views. The experiments demonstrate that our approaches achieve results comparable to those of state-of-the-art approaches

Evolutionary Computation

This book presents several recent advances on Evolutionary Computation, specially evolution-based optimization methods and hybrid algorithms for several applications, from optimization and learning to pattern recognition and bioinformatics. This book also presents new algorithms based on several analogies and metafores, where one of them is based on philosophy, specifically on the philosophy of praxis and dialectics. In this book it is also presented interesting applications on bioinformatics, specially the use of particle swarms to discover gene expression patterns in DNA microarrays. Therefore, this book features representative work on the field of evolutionary computation and applied sciences. The intended audience is graduate, undergraduate, researchers, and anyone who wishes to become familiar with the latest research work on this field