Системи виявлення Web-сервісів в сервіс-орієнтованій архітектурі: проблеми і рішення

З появою парадигми сервіс-орієнтованого обчислення і зростаючою кількістю доступних Web-сервісів в Інтернеті посилюється запит на засоби для виконання виявлення, вибору, композиції і виклику Web-сервісів. На сьогодні запропонована велика кількість підходів щодо виявлення Web-сервісів, яка обумовлена низкою задач та їх можливими рішеннями при побудові систем виявлення Web-сервісів. У цій статті проведено аналітичний огляд задач, які постають при розробці і функціонуванні таких систем, та наведені існуючі підходи до їх вирішення. Показано, що проблема виявлення Web-сервісів може бути висвітлена в дескриптивній логіці на основі «найкращого покриття»

Uma abordagem para composição semiautomática de serviços baseada em sugestões semânticas

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Ciência da Computação, Florianópolis, 2015.O uso de semântica na Web tem o intuito de permitir que as informações possam sem processadas por máquinas, geralmente através de significados definidos por ontologias, que são uma especificação formal e explícita de um conceito compartilhado. Com Web Services é possível a invocação de funcionalidade de softwares através de interfaces bem definidas. A utilização de semântica para descrição de Web Services possibilita ainda a automação, total ou parcial, do processo de criação de composições de serviços, que mostra-se necessária quando um único serviço não consegue prover toda a funcionalidade desejada pelo cliente. Na literatura existem vários esforços para buscar automação no processo de composição de serviços com base na utilização de descrição semântica. A completa automação do processo de composição de serviço vem associada ao alto custo computacional e à exclusão do usuário do processo. Esse trabalho apresenta uma abordagem hibrida, semiautomática, chamada de S3M, na qual há participação do usuário no processo de composição de serviços, somada a sugestões de operações que são compatíveis com a composição sendo criado. Isso é feito através do match semântico entre as entradas das operações candidatas junto às saídas das operações contidas na composição sendo criada, somada a outras métricas. Como a qualidade da sugestão depende diretamente das ontologias associadas ao serviços, a avaliação da proposta ficou limitada a testes de desempenho e simulação do comportamento do algoritmo em determinados cenários. Abstract : The use of semantic in the Web aims to make possible the processing of information by machines, usually through a well defined meaning in ontologies, i.e. a formal explicit specification of a shared conceptualization. With Web Service it is possible the invocacional of software functionality through interfaces. Semantic is used to add meaning to Web Services operations, inputs and outputs. The use of semantic description in Web Services also allows either full or partial automation of the service composition creation process, which is necessary when a single service cannot provide all features required by the client. There are several efforts in literature seeking automation of the service composition process based on the use of semantic descriptions. The complete automation on the service composition process results in a high computational cost and in excluding the user from the process. This work presents a hybrid (i.e. semi-automatic) approach, called S3M. In which the user takes part in the service composition process, receiving suggestions of services that are compatible with the composition during its creation. This is made through the semantic match between the inputs of the candidates operations and the outputs of the operations inside the composition been designed, with another metrics. The quality of the suggestion are directly dependent with the ontologies associated with the services, making the evaluation of the presented work limited to performance tests and simulation, where the behavior of de suggestion mechanism could be analyzed

Uma abordagem automática para descoberta e composição de serviços web semânticos

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Ciência da Computação, Florianópolis, 2012A adição de semântica à descrição de Serviços Web visa permitir a automação dos processos de descoberta e composição de serviços. Para que isso seja possível, é necessário que sejam desenvolvidas ferramentas que façam com que esses processos sejam realizados dinamicamente, sem a necessidade de intervenção humana. Diversos trabalhos na área de Web Semântica têm explorado a descoberta e a composição de Serviços Web através da descrição semântica das suas funcionalidades. Este trabalho apresenta uma abordagem para a descoberta e a composição de Serviços Web Semânticos de forma automática. Mediante o envio de uma requisição com a descrição das funcionalidades de um serviço, a abordagem proposta possibilita que composições sejam estabelecidas quando um único Serviço Web não é suficiente para atender as necessidades dos usuários. Por meio de anotações semânticas baseadas em SAWSDL (Semantic Annotations for WSDL), a abordagem proposta realiza o matching semântico das funcionalidades dos serviços web disponíveis em repositórios de serviços com as informações enviadas na requisição e constrói um grafo de composições. No final da construção do grafo, um algoritmo analisa se dois ou mais caminhos levam à mesma informação desejada pelo usuário. Caso isso aconteça, uma função é aplicada para cada caminho, a fim de selecionar aquele com o menor grau de divergência semântica. A proposta da abordagem apresentada é criar composições de serviços web em tempo de requisição de modo que sejam capazes de combinar serviços pré-existentes para criar um novo serviço, tirando proveito das funcionalidades oferecidas por cada um e combinando-as a fim de oferecer funcionalidades ainda mais complexas e até inexistentes. Dessa forma, a abordagem torna o processo de busca e composição de serviços web capaz de informar não apenas serviços individuais, mas também composições de serviços. Como contribuições deste trabalho citam-se: um algoritmo para a seleção de composições baseado na qualidade semântica das mesmas e um protótipo em conjunto com uma infraestrutura para a descoberta e a composição de serviços web.Abstract : The addition of semantic to web services description allows the automation of the discovery and composition process. However, tools must be developed to allow these processes be performed dynamically without human intervention. Several studies in the area of the Semantic Web have explored the discovery and composition of Web Services through semantic description of its functionality. This work presents an approach for automatic discovery and composition of semantic web services. By sending a request with the description of a service functionality, the proposed approach enables compositions to be established when a single web service is not sufficient to meet the user needs. Through semantic annotations based on SAWSDL (Semantic Annotations for WSDL), the proposed approach performs the semantic matching of Web services capabilities available in services repositories with the information sent in the request and builds a composition graph. At the end of the construction of the graph, an algorithm analyzes if two or more paths lead to the same information desired by the user. If this happens, a function is applied to each path in order to select the one with the lowest semantic mismatch degree. The purpose of the presented approach is to create compositions of web services at request time so that they are able to combine pre-existing services to create a new service, taking advantage of the functionality offered by each and combining them to provide functionality yet more complex and even non-existent. Thus, the approach makes the process of discovery and composition of web services return not only individual services, but also compositions of services. The main contributions of this work are: an algorithm for selection of compositions based on its semantics quality, a prototype and an infrastructure for discovery and composition of web services

A Semantically Enhanced Approach for Orchestration of Web Services in Factory Automation Systems

The Service-oriented Architecture (SOA) paradigm makes it possible to build systems from several independent components. Most typically, web services are chosen as the building blocks of such a system. A web service is essentially a passive software entity, which listens for request messages sent to it over the network, possibly reacts to the requests by performing some operations, and finally sends response messages to the request senders. The traditional application domain of web services belongs to the so-called IT domain. While opening new horizons in software development life-cycles, web services have been adopted in various new application domains, including the domain of factory automation (software development for factory automation). Indeed, recent research projects have experimented with controlling production system equipment through web service interfaces. When migrated from pure software to the physical realm involving industrial equipment, web services set additional demands for the application domains. For example, since the domains involve operations with physical effects, roll-back or application recovery procedures become challenging. This research work targets the orchestration of factory automation systems encapsulated as web services and presents various techniques for overcoming the difficulties. Orchestrating web services to accomplish a complicated production task can be difficult due to the transitoriness of both production equipment states and the set of available web services. Nevertheless, the selection of appropriate web services can be facilitated by augmenting each service with semantic information describing its conditions and effects. Web services augmented with such descriptions are termed semantic web services. While Web Ontology Language, OWL, is ideal for describing application domain concepts and property relationships, the OWL-S ontology, which is based on OWL, has been specifically developed for describing web services. Once the semantic service descriptions have been analyzed to find the appropriate web services, the selected services can be invoked using their syntactic WSDL descriptions. In addition to automated web service selection, semantic descriptions allow the composition of web services to achieve production tasks. Service composition involves first analyzing the descriptions to determine the appropriate service invocation process for achieving the desired goal and then executing the process. This dissertation presents an approach in which the production equipment and their states are represented using an ontology, and the model is dynamically used in decision-making. In particular, the devices in the considered production systems provide web service interfaces through which they can be controlled, while semantic web service descriptions formulated in OWL-S make it possible to determine the conditions and effects of invoking the web services. The approach presented in this research work additionally involves a set of specialized web services that co-operate to achieve production goals using the domain web services. One of the services maintains a semantic model of the current system state, while another uses the model to compose the domain web services so that they jointly achieve the desired goals. The semantic model of the system is automatically updated based on event notifications sent by the domain services. Software agents controlling production devices must maintain an up-to-date view of the physical world state in order to efficiently reason and plan their actions. Especially in a factory automation system, the world state undergoes rapid evolution, and the world view must remain synchronized with the changes. This research discusses two approaches to updating the world view based on event notifications sent by web services representing production devices in a manufacturing system. One of the approaches is based on separately specified update rules, and one automatically uses semantic web service descriptions formulated in OWL-S. While all of the examples presented in this research work specifically focus on the factory automation domain, the presented approaches are applicable to all domains involving semantic web services. Semantic Web Service descriptions facilitate the automated discovery and composition of web services. Particularly in the production system domain, the service condition and effect descriptions are essential in selecting the appropriate service or service composition for a given task. OWL-S is one of the most popular semantic web service description languages, and due to its XML syntax, OWL-S can be effortlessly incorporated into service WSDL descriptions. However, developing OWL-S documents for each service instance is laborious. This dissertation presents an approach to automatically generating executable OWL-S descriptions from semantically annotated service WSDL files. Computing clouds facilitate rapid and effortless resource allocation. Cloud consumers can generally be ignorant of the physical computing resources used or their geographical location, as the resources are abstracted into a commodity that can be dynamically leased from the cloud provider. In particular, Infrastructure-as-a-Service clouds allow clients to dynamically lease virtual machines that behave similarly to physical servers. However, executing an application by directly using computing cloud resources is complicated and typically involves similar steps as installing and executing an application on a physical machine. Moreover, starting numerous application instances on a single virtual machine may result in poor performance. Thus, this dissertation considers the development of a web service that facilitates the use of cloud resources by abstracting them. When the web service is used, an application can be effortlessly started in a computing cloud by invoking simple web service operations. Furthermore, when multiple applications are started, the workload can be automatically distributed between several virtual machines, resulting in higher performance. To conclude, the results presented in this research work demonstrate that semantic web service descriptions can indeed facilitate automatic web service composition and invocation. However, the effort of developing semantic web service descriptions can partly undermine the benefits achieved through their application. Therefore, new tools and methods should be developed to minimize the effort of developing such descriptions