Service Discovery and Composition Based on Contracts and Choreographic Descriptions

The authors discuss the interplay between the notions of contract compliance, contract refinement, and choreography conformance in the context of service oriented computing, by considering both synchronous and asynchronous communication. Service contracts are specified in a language independent way by means of finite labeled transition systems. In this way, the theory is general and foundational as the authors abstract away from the syntax of contracts and simply assume that a contract language has an operational semantics defined in terms of a labeled transition system. The chapter makes a comparative analysis of synchronous and asynchronous communication. Concerning the latter, a realistic scenario is considered in which services are endowed with queues used to store the received messages. In the simpler context of synchronous communication, the authors are able to resort to the theory of fair testing to provide decidability results.

Structural Interoperability as a Basis for Service Adaptability

Web Services appeared essentially as an interoperability solution and REST as a closer match to the semantics of protocols such as HTTP. Clearly influenced by the original browsing goals of the Web, these technologies are not native solutions to the service-oriented paradigm, exhibit limitations to interoperability, and behavior has to be implemented in a separate language. Web Services offer a WSDL document to describe them, but assume that complex data use the same schema in both interacting services, which increases their coupling. This chapter discusses interoperability, from the perspective of both the consumer (compliance) and provider (conformance) services, and it argues that compliance is a weaker requirement for service interoperability than conformance and should be the cornerstone to decrease coupling and to favor adaptability. Structural interoperability is used, given that the lifecycles of distributed resources are decoupled. Metrics to quantify adaptability, based on similarity and decoupling, are proposed.

Flexible Coordination Techniques for Dynamic Cloud Service Collaboration

The provision of individual, but also composed services is central in cloud service provisioning. The authors describe a framework for the coordination of cloud services, based on a tuple-space architecture which uses an ontology to describe the services. Current techniques for service collaboration offer limited scope for flexibility. They are based on statically describing and compositing services. With the open nature of the web and cloud services, the need for a more flexible, dynamic approach to service coordination becomes evident. In order to support open communities of service providers, there should be the option for these providers to offer and withdraw their services to/from the community. For this to be realised, there needs to be a degree of self-organisation. The authors’ techniques for coordination and service matching aim to achieve this through matching goal-oriented service requests with providers that advertise their offerings dynamically. Scalability of the solution is a particular concern that will be evaluated in detail.

A Framework for Situation-Aware Adaptation of Service-Based Applications

This work presents Situation Action Networks, a new framework for modeling Service-Based Application adaptation triggered by interesting or critical situations. The framework is based on a goal model able to track at run time the fulfillment of goals. Situation Action Networks are tree-like hierarchical structures which enable goal decomposition into sub-goals and primitive actions in a recursive fashion which provides goal seeking execution plans, as a sequence of primitive actions. Situation Action Networks are dynamic and can evolve at runtime by using their inherent planning capabilities.

From SOA to Pervasive Service Ecosystems

Emerging pervasive computing scenarios require open service frameworks promoting situated adaptive behaviors and supporting diversity in services and long-term ability to evolve. The authors argue that this calls for a nature-inspired approach in which pervasive services are modeled and deployed as autonomous individuals in an ecosystem of other services, data sources, and pervasive devices. They discuss how standard service-oriented architectures have to evolve to tackle the above issues, present a general architecture based on a shared spatial substrate mediating interactions of all the individual services of the pervasive computing system, and finally show that this architecture can be implemented relying primarily on standard W3C Semantic Web technologies, like RDF and SPARQL. A use case of adaptive pervasive displays for crowd steering applications is exploited as reference example.

Mining Lifecycle Event Logs for Enhancing Service-based Applications

Service-Oriented Architectures (SOAs), and traditional enterprise systems in general, record a variety of events (e.g., messages being sent and received between service components) to proper log files, i.e., event logs. These files constitute a huge and valuable source of knowledge that may be extracted through data mining techniques. To this end, process mining is increasingly gaining interest across the SOA community. The goal of process mining is to build models without a priori knowledge, i.e., to discover structured process models derived from specific patterns that are present in actual traces of service executions recorded in event logs. However, in this work, the authors focus on detecting frequent sequential patterns, thus considering process mining as a specific instance of the more general sequential pattern mining problem. Furthermore, they apply two sequential pattern mining algorithms to a real event log provided by the Vienna Runtime Environment for Service-oriented Computing, i.e., VRESCo. The obtained results show that the authors are able to find services that are frequently invoked together within the same sequence. Such knowledge could be useful at design-time, when service-based application developers could be provided with service recommendation tools that are able to predict and thus to suggest next services that should be included in the current service composition.

Towards Event-Driven Context-Aware Web Services

Web services provide a successful way to communicate distributed applications, in a platform-independent and loosely coupled manner. Even though there are examples of good practice for the design, development, and management of web services, getting services to be context-aware is still under investigation. Current proposals require communication with an external context server or manager, slowing down service performance. In this work, the authors propose an architecture which utilizes complex event processing for detecting context events relevant to the services in question and an aspect-oriented adaptation, maintaining a loosely coupled service implementation as well as keeping its main functionality structure without adding any context-related intrusive code.

Reusing Services through Context-Aware Discovery and Adaptation in Pervasive Systems

Reusing of software entities, such as components or services, to develop software systems has matured in recent years. However, it has not become standard practice yet, since using pre-existing software requires the selection, composition, adaptation, and evolution of prefabricated software parts. Recent research approaches have independently tackled the discovery, composition, or adaptation processes. On the one hand, the discovery process aims at discovering the most suitable services for a request. On the other hand, the adaptation process solves, as automatically as possible, mismatch cases which may be given at the different interoperability levels among interfaces by generating a mediating adaptor based on an adaptation contract. In this chapter, the authors present the DAMASCo framework, which focuses on composing services in mobile and pervasive systems accessed through their public interfaces, by means of context-aware discovery and adaptation. DAMASCo has been implemented and evaluated on several examples.

Adaptive ESB Infrastructure for Service Based Systems

Service-based systems increasingly need adaptation capabilities to agilely respond to unexpected changes in their business or execution environment. Although service orientation constitutes a promising approach to achieve this goal, current methods and technologies do not fully support automatic and dynamic adaptation at runtime. In turn, the Enterprise Service Bus (ESB), one of the preferred middleware technologies to support the development of service-based systems, provides several built-in mediation capabilities (e.g. message transformation), which can be used to perform adaptation actions. However, the configuration of these capabilities cannot usually be performed at runtime. This chapter proposes an Adaptive ESB Infrastructure which, based on the mediation capabilities provided by ESBs, can respond to adaptation requirements in service-based systems in an automatic and dynamic way at runtime. The chapter also specifies how the proposed solutions can be used to deal with concrete situations including response time degradation, services saturation, and changes in services contracts.

Adaptive Future Internet Applications

Adaptive capabilities are essential to guarantee the proper execution of Web services and service-oriented applications once dynamic changes are not exceptions but the rule. The importance of adaptive capabilities significantly increases in the context of Future Internet (FI) applications will have to autonomously adapt to changes on service provisioning, availability of things and content, computing resources, and network connectivity. Current solutions for adaptive Web services and adaptive service-based applications will be challenged in such a setting because they fall short to support essential characteristics of FI applications. This chapter analyzes and justifies the need for the transition from adaptive Web services and service-based applications to adaptive FI applications. Based on two real-world use cases from multimedia and logistics, the authors examine where current solutions fall short to properly address the adaptive needs of FI applications. They propose future research challenges that should be considered in adaptive FI applications.