Capabilities : describing what services can do

The ability of agents and services to automatically locate and interact with unknown partners is a goal for both the semantic web and web services. This, \serendipitous interoperability", is hindered by the lack of an explicit means of describing what services (or agents) are able to do, that is, their capabilities. At present, informal descriptions of what services can do are found in \documentation" elements; or they are somehow encoded in operation names and signatures. We show, by ref- erence to existing service examples, how ambiguous and imprecise capa- bility descriptions hamper the attainment of automated interoperability goals in the open, global web environment. In this paper we propose a structured, machine readable description of capabilities, which may help to increase the recall and precision of service discovery mechanisms. Our capability description draws on previous work in capability and process modeling and allows the incorporation of external classi¯cation schemes. The capability description is presented as a conceptual meta model. The model supports conceptual queries and can be used as an extension to the DAML-S Service Pro¯le.

Information extraction from web services : a comparison of Tokenisation algorithms

Most web service discovery systems use keyword-based search algorithms and, although partially successful, sometimes fail to satisfy some users information needs. This has given rise to several semantics-based approaches that look to go beyond simple attribute matching and try to capture the semantics of services. However, the results reported in the literature vary and in many cases are worse than the results obtained by keyword-based systems. We believe the accuracy of the mechanisms used to extract tokens from the non-natural language sections of WSDL files directly affects the performance of these techniques, because some of them can be more sensitive to noise. In this paper three existing tokenization algorithms are evaluated and a new algorithm that outperforms all the algorithms found in the literature is introduced.

Deriving artefact-centric interfaces for overloaded web services

We present a novel framework and algorithms for the analysis of Web service interfaces to improve the efficiency of application integration in wide-spanning business networks. Our approach addresses the notorious issue of large and overloaded operational signatures, which are becoming increasingly prevalent on the Internet and being opened up for third-party service aggregation. Extending upon existing techniques used to refactor service interfaces based on derived artefacts of applications, namely business entities, we propose heuristics for deriving relations between business entities, and in turn, deriving permissible orders in which operations are invoked. As a result, service operations are refactored on business entity CRUD which then leads to behavioural protocols generated, thus supportive of fine-grained and flexible service discovery, composition and interaction. A prototypical implementation and analysis of web services, including those of commercial logistic systems (Fedex), are used to validate the algorithms and open up further insights into service interface synthesis.

Discovering behavioural interfaces for overloaded web services

The growth of APIs and Web services on the Internet, especially through larger enterprise systems increasingly being leveraged for Cloud and software-as-a-service opportuni- ties, poses challenges to improving the efficiency of integration with these services. Interfaces of enterprise systems are typically larger, more complex and overloaded, with single operation having multiple data entities and parameter sets, supporting varying requests, and reflecting versioning across different system releases, compared to fine-grained operations of contemporary interfaces. We propose a technique to support the refactoring of service interfaces by deriving business entities and their relationships. In this paper, we focus on the behavioural aspects of service interfaces, aiming to discover the sequential dependencies of operations (otherwise known as protocol extraction) based on the entities and relationships derived. Specifically, we propose heuristics according to these relationships, and in turn, deriving permissible orders in which operations are invoked. As a result of this, service operations can be refactored on business entity CRUD lines, with explicit behavioural protocols as part of an interface definition. This supports flexible service discovery, composition and integration. A prototypical implementation and analysis of existing Web services, including those of commercial logistic systems (Fedex), are used to validate the algorithms proposed through the paper.

Uso de ontologia em serviço de contexto e descoberta de recursos para autoadaptação de sistemas.

Aplicações cientes de contexto precisam de mecanismos para recuperar informações sobre o seu contexto de execução. Com base no contexto atual, tais aplicações são capazes de se autoadaptar para fornecer informações e serviços adequados aos seus usuários. A abordagem comum para infraestruturas de apoio às aplicações sensíveis ao contexto fornece serviços para a descoberta de recursos através da utilização de pares e motores que executam apenas correspondência sintática. Esta abordagem não considera as possíveis relações semânticas entre as palavras-chave usadas. Portanto, a sua expressividade semântica limitada, leva a um serviço de descoberta que provê baixa taxa de recuperação e baixa acurácia. Este trabalho apresenta a utilização de uma outra abordagem para o serviço de contexto e descoberta, que utiliza ontologias para representar os recursos do contexto de execução e capturar a semântica da consulta do usuário, melhorando assim o processo de descoberta para a autoadaptação de sistemas sensíveis ao contexto. A abordagem proposta oferece também pontos de extensão para as aplicações clientes através da utilização de outras ontologias. Esta abordagem foi integrada à infraestrutura CDRF, de forma a adicionar semântica aos serviços desenvolvidos neste projeto. Exemplos de aplicações são também propostos para demonstrar a utilização dos novos serviços.

支持广域网的协作式服务发现机制

服务发现是网络分布式环境下进行信息共享、数据集成、流程协作的前提。广域网下的服务发现机制必须在无可直接利用的广播和组播机制上解决系统的规模伸缩性问题,以合理的代价为用户提供高效的服务发现机制。采用覆盖网络体系结构,并实际构建了具有一定可伸缩性的服务发现系统Service CatalogNet。Service CatalogNet基于分布存储的服务信息和后缀树形式的服务信息索引,实现了协作式服务发现机制,特别提供了QoS感知的服务发现机制,即可基于客户的QoS指标生成应用层选播/多播路由,进而实现服务发现。实验结果表明,该服务发现机制在发现性能上优于LDAP实现。

一种网格环境的服务查找算法

网格计算为大规模Internet应用提供了必要的基础架构，服务查找是网格计算的重要研究内容之一。但是目前常见的服务查找算法不太适应于网格环境的分散性和松耦合等特点。提出了一种分布式的、综合考虑网络延迟和节点负载情况及处理能力、适合于网格环境的服务查找算法DDCA。实验结果表明，DDCA算法能有效提高网格环境下应用的整体性能。

移动Ad hoc网络服务发现协议

介绍移动Ad hoc网络的应用前景和主要研究内容,阐述服务协议的重要性以及服务发现协议中的基本概念,针对现有的移动Ad hoc网络服务发现协议的核心技术和设计思想进行分析,选取几种典型的服务发现协议进行对比,总结得出各类服务发现协议的优缺点和适用范围,并指出该领域的进一步研究方向.

普适环境下服务发现的语义支持机制

随着计算能力和通信能力的增强，计算设备所占用的体积也越来越小，各种新形态的传感器、移动设备及无线网络设备日趋普及。这极大地促进了以无线、移动和嵌入式设备为基础的普适计算模式的形成和发展。普适环境下的服务发现机制可使得用户能够使用各种移动设备无缝的、随时随地的共享和访问各种服务信息。 普适环境中的网络异构性和动态性，以及服务的多样性和异构性，均对服务发现提出了新的挑战。目前学术界和工业界在服务发现方面进行了不少的探索和研究，当前的一些服务发现协议或系统比如SLP、UPnP、INS等，一般基于语法的方法描述服务，主要关注服务的功能性需求，但基于关键字来匹配请求和服务描述，在普适环境下常常会导致较差的匹配结果。 针对服务发现在普适环境中的新需求，本文基于XML定义了一种轻量级的服务语义建模语言SML，SML定义了丰富的数据类型，以模板和属性的方式定义各领域的实体，可以表达丰富的语义知识；同时，本文以轻量级的推理引擎Jess为依托，将用服务建模语言定义的各应用领域的服务模板和语义知识自动转换成Jess的推理规则和事实。本文定义了一种类似XPath的服务查询语言规范，并在支持精确匹配的基础上，提出了服务的近似匹配策略，提供了各种的近似计算规则。鉴于不同用户对服务的各属性有不同的偏好程度，还提出了基于用户偏好的服务匹配策略。动态的上下文信息是服务匹配过程的重要考虑因素。本文以Jess规则来匹配服务和用户的上下文，选择适合于用户当前情况的服务。对服务各种QoS的描述支持也是服务语义建模语言提供的功能之一，为此，本文还提出了一种基于Pareto最优的服务选择策略，根据服务的QoS以及服务与请求的匹配程度来选择Pareto最优的服务。本文的上述工作已实现到服务发现系统Service CatalogNet Extended中。

多服务发现协议的互操作框架研究

服务发现协议（Service Discovery Protocol）是支持程序和设备自动发现并访问网络中所需服务的协议，是分布式环境特别是普适环境下进行资源共享、数据集成、流程协作的前提。目前学术界和工业界已经提出了多种服务发现协议，如UPnP SSDP、SLP、Salutation、Bluetooth SDP。这些服务发现协议提供了类似的功能，但在适用网络类型、描述模型、发现机制、服务使用方式等方面存在着高度的异构性，导致使用不同服务发现协议的设备之间无法直接进行交互，从而限制了服务使用者和服务提供者之间的交互范围及交互能力。同时这其中的一些协议已经成为事实上的工业标准，但目前并没有一个能够适用于所有场景并占据整个市场，并且在很长的一段时间内不可能出现一个通用的协议来取而代之，同时，要求服务请求者和服务提供者同时支持多种服务发现协议是不现实的，因此迫切需要一种互操作框架来实现各种服务发现协议之间的互操作，从而允许服务使用者能够以其自有的方式在网络上发现并使用所需的各种服务，而不用考虑服务发布所采用的具体服务发现协议及调用方式的不同。 目前学术界和工业界在服务发现协议的互操作方面进行了不少探索和研究，但在互操作对象的可扩展性及互操作的透明性、范围方面仍存在不少问题尚未得到有效地解决。 本文主要研究跨网络环境下的服务发现协议的互操作。本文基于抽象语义信息的互操作模型，综合考虑了上下文信息，采用分阶段事件驱动的技术处理并发请求，设计并实现了具有透明性、可扩展性、高效性的服务发现协议互操作框架（Service CatlogNet Interoperable Framework，SCNIF），本文设计与实现了三种服务发现协议（UPnP SSDP、SLP、SCN）的互操作插件，还给出了新加入服务发现协议的互操作插件的实现方案。

服务发现机制的设计与实现

随着网络的普及和各类设备的智能化、移动化，普遍互联和动态移动构成了当前计算环境的主要特征。服务发现协议帮助用户在各类分布式环境下找到所需的服务，即，存在于网络中，可以被发布、发现和使用的任何软件或硬件资源。服务发现是网络分布式环境下进行信息共享、数据集成、流程协作的前提，更是普适计算环境的基础设施。 学术界和工业界在服务发现方面已经进行了不少的探索和研究，但是目前Internet/Intranet、MANET的规模越来越大，网络中的服务种类与数量剧增，适用于上述网络环境的服务发现系统应该具备高效、准确、低通信量和规模可伸缩的特性，另外，由于网络的动态性，系统需要具有一定的容错能力。针对于上述网络环境的服务发现研究相对较少且不成熟，还存在较多问题需要解决。 本文以服务描述模型SDMDHD为基础，针对于稠密部署的大规模MANET环境，设计了相应的服务发现机制，并在SCN4M（Service CatalogNet for MANET）系统中实现了该发现机制；针对于服务种类丰富、数量很大的大规模Internet/Intranet环境，设计了相应的服务发现机制，并将该机制实现在SCN4I（Service CatalogNet for Internet/Intranet）系统中。两个系统均对服务信息进行了摘要，并以服务信息的摘要为基础构建了分布式后缀树索引机制，它确保了高效、准确、低通信量的服务发现过程，从而使得系统具备规模可伸缩性。以索引机制为基础，两个系统提供了基于协作的选播/多播服务发现策略。针对网络动态性，两个系统均采用分布式信息冗余存储策略，一定程度上解决了节点失效引发的信息丢失问题。另外，SCN4M实现了基于内容寻址的应用层路由方案，SCN4I实现了虚拟环状空间中基于内容的消息转发机制，为解决节点动态加入和离开问题奠定了基础。

Framework for middleware executed on mobile devices

Die ubiquitäre Datenverarbeitung ist ein attraktives Forschungsgebiet des vergangenen und aktuellen Jahrzehnts. Es handelt von unaufdringlicher Unterstützung von Menschen in ihren alltäglichen Aufgaben durch Rechner. Diese Unterstützung wird durch die Allgegenwärtigkeit von Rechnern ermöglicht die sich spontan zu verteilten Kommunikationsnetzwerken zusammen finden, um Informationen auszutauschen und zu verarbeiten. Umgebende Intelligenz ist eine Anwendung der ubiquitären Datenverarbeitung und eine strategische Forschungsrichtung der Information Society Technology der Europäischen Union. Das Ziel der umbebenden Intelligenz ist komfortableres und sichereres Leben. Verteilte Kommunikationsnetzwerke für die ubiquitäre Datenverarbeitung charakterisieren sich durch Heterogenität der verwendeten Rechner. Diese reichen von Kleinstrechnern, eingebettet in Gegenstände des täglichen Gebrauchs, bis hin zu leistungsfähigen Großrechnern. Die Rechner verbinden sich spontan über kabellose Netzwerktechnologien wie wireless local area networks (WLAN), Bluetooth, oder UMTS. Die Heterogenität verkompliziert die Entwicklung und den Aufbau von verteilten Kommunikationsnetzwerken. Middleware ist eine Software Technologie um Komplexität durch Abstraktion zu einer homogenen Schicht zu reduzieren. Middleware bietet eine einheitliche Sicht auf die durch sie abstrahierten Ressourcen, Funktionalitäten, und Rechner. Verteilte Kommunikationsnetzwerke für die ubiquitäre Datenverarbeitung sind durch die spontane Verbindung von Rechnern gekennzeichnet. Klassische Middleware geht davon aus, dass Rechner dauerhaft miteinander in Kommunikationsbeziehungen stehen. Das Konzept der dienstorienterten Architektur ermöglicht die Entwicklung von Middleware die auch spontane Verbindungen zwischen Rechnern erlaubt. Die Funktionalität von Middleware ist dabei durch Dienste realisiert, die unabhängige Software-Einheiten darstellen. Das Wireless World Research Forum beschreibt Dienste die zukünftige Middleware beinhalten sollte. Diese Dienste werden von einer Ausführungsumgebung beherbergt. Jedoch gibt es noch keine Definitionen wie sich eine solche Ausführungsumgebung ausprägen und welchen Funktionsumfang sie haben muss. Diese Arbeit trägt zu Aspekten der Middleware-Entwicklung für verteilte Kommunikationsnetzwerke in der ubiquitären Datenverarbeitung bei. Der Schwerpunkt liegt auf Middleware und Grundlagentechnologien. Die Beiträge liegen als Konzepte und Ideen für die Entwicklung von Middleware vor. Sie decken die Bereiche Dienstfindung, Dienstaktualisierung, sowie Verträge zwischen Diensten ab. Sie sind in einem Rahmenwerk bereit gestellt, welches auf die Entwicklung von Middleware optimiert ist. Dieses Rahmenwerk, Framework for Applications in Mobile Environments (FAME²) genannt, beinhaltet Richtlinien, eine Definition einer Ausführungsumgebung, sowie Unterstützung für verschiedene Zugriffskontrollmechanismen um Middleware vor unerlaubter Benutzung zu schützen. Das Leistungsspektrum der Ausführungsumgebung von FAME² umfasst: • minimale Ressourcenbenutzung, um auch auf Rechnern mit wenigen Ressourcen, wie z.B. Mobiltelefone und Kleinstrechnern, nutzbar zu sein • Unterstützung für die Anpassung von Middleware durch Änderung der enthaltenen Dienste während die Middleware ausgeführt wird • eine offene Schnittstelle um praktisch jede existierende Lösung für das Finden von Diensten zu verwenden • und eine Möglichkeit der Aktualisierung von Diensten zu deren Laufzeit um damit Fehlerbereinigende, optimierende, und anpassende Wartungsarbeiten an Diensten durchführen zu können Eine begleitende Arbeit ist das Extensible Constraint Framework (ECF), welches Design by Contract (DbC) im Rahmen von FAME² nutzbar macht. DbC ist eine Technologie um Verträge zwischen Diensten zu formulieren und damit die Qualität von Software zu erhöhen. ECF erlaubt das aushandeln sowie die Optimierung von solchen Verträgen.

Implementing Policy Management through BDI

The requirement for Grid middleware to be largely transparent to individual users and at the same time act in accordance with their personal needs is a difficult challenge. In e-science scenarios, users cannot be repeatedly interrogated for each operational decision made when enacting experiments on the Grid. It is thus important to specify and enforce policies that enable the environment to be configured to take user preferences into account automatically. In particular, we need to consider the context in which these policies are applied, because decisions are based not only on the rules of the policy but also on the current state of the system. Consideration of context is explicitly addressed, in the agent perspective, when deciding how to balance the achievement of goals and reaction to the environment. One commonly-applied abstraction that balances reaction to multiple events with context-based reasoning in the way suggested by our requirements is the belief-desire-intention (BDI) architecture, which has proven successful in many applications. In this paper, we argue that BDI is an appropriate model for policy enforcement, and describe the application of BDI to policy enforcement in personalising Grid service discovery. We show how this has been implemented in the myGrid registry to provide bioinformaticians with control over the services returned to them by the service discovery process.

Towards a Protocol for the Attachment of Semantic Descriptions to Grid Services

Service discovery in large scale, open distributed systems is difficult because of the need to filter out services suitable to the task at hand from a potentially huge pool of possibilities. Semantic descriptions have been advocated as the key to expressive service discovery, but the most commonly used service descriptions and registry protocols do not support such descriptions in a general manner. In this paper, we present a protocol, its implementation and an API for registering semantic service descriptions and other task/user-specific metadata, and for discovering services according to these. Our approach is based on a mechanism for attaching structured and unstructured metadata, which we show to be applicable to multiple registry technologies. The result is an extremely flexible service registry that can be the basis of a sophisticated semantically-enhanced service discovery engine, an essential component of a Semantic Grid.

State aware WSDL

With the recent innovations in stateful web services, they are now being used to support the construction of distributed systems using software as a service. While the state of web services is preserved, the state is still hidden from clients thus searches for both functionality and state remains a two step process. Proposed in this report is the Resources Via Web Instances (RVWI) framework. RVWI grants to web services the ability to include their state and characteristics in their WSDL. This was done by allowing snapshots (instances) of a web service to be listed in the WSDL of the web service. Instances were utilised as they contain state and characteristic information directly from the web service. Thanks to the inclusion of state and characteristics, queries for web services can now be carried out on the availability of a web service and the 'dimensions' of resources..