Resource Oriented Modelling: Describing Restful Web Services Using Collaboration Diagrams

The popularity of Resource Oriented and RESTful Web Services is increasing rapidly. In these, resources are key actors in the interfaces, in contrast to other approaches where services, messages or objects are. This distinctive feature necessitates a new approach for modelling RESTful interfaces providing a more intuitive mapping from model to implementation than could be achieved with non-resource methods. With this objective we propose an approach to describe Resource Oriented and RESTful Web Services based on UML collaboration diagrams. Then use it to model scenarios from several problem domains, arguing that Resource Oriented and RESTful Web Services can be used in systems which go beyond ad-hoc integration. Using the scenarios we demonstrate how the approach is useful for: eliciting domain ontologies; identifying recurring patterns; and capturing static and dynamic aspects of the interface

Security for Grid Services

Grid computing is concerned with the sharing and coordinated use of diverse resources in distributed "virtual organizations." The dynamic and multi-institutional nature of these environments introduces challenging security issues that demand new technical approaches. In particular, one must deal with diverse local mechanisms, support dynamic creation of services, and enable dynamic creation of trust domains. We describe how these issues are addressed in two generations of the Globus Toolkit. First, we review the Globus Toolkit version 2 (GT2) approach; then, we describe new approaches developed to support the Globus Toolkit version 3 (GT3) implementation of the Open Grid Services Architecture, an initiative that is recasting Grid concepts within a service oriented framework based on Web services. GT3's security implementation uses Web services security mechanisms for credential exchange and other purposes, and introduces a tight least-privilege model that avoids the need for any privileged network service.Comment: 10 pages; 4 figure

Towards two-stage service representation and reasoning: from lightweight annotations to comprehensive semantics

Semantics are used to mark up a wide variety of data-centric Web resources but are not used to annotate online functionality in significant numbers. That is despite considerable research dedicated to Semantic Web Services (SWS). This has led to the emergence of a new Linked Services approach with simplified and less costly to produce service models, which targets a wider audience and allows even non-SWS developers to annotate services. However, such models merely aim at enabling semantic search by humans or automated service clustering rather than automation of service tasks such as discovery or orchestration. Thus, more expressive solutions are still required to achieve automated discovery and orchestration of services. In this paper, we describe our investigation into combining the strengths of two distinct approaches to modeling semantic Web services – 'lightweight' Linked Services and 'heavyweight' SWS automation - into a coherent SWS framework. In our vision, such integration is achieved by means of model cross-referencing and model transformation and augmentation

Comprehensive service semantics and light-weight Linked Services: towards an integrated approach

Semantics are used to mark up a wide variety of data-centric Web resources but, are not used in significant numbers to annotate online services — that is despite considerable research dedicated to Semantic Web Services (SWS). This is partially due to the complexity of comprehensive SWS models aiming at automation of service-oriented tasks such as discovery, composition, and execution. This has led to the emergence of a new approach dubbed Linked Services which is based on simplified service models that are easier to populate and interpret and accessible even to non-experts. However, such Minimal Service Models so far do not cover all execution-related aspects of service automation and merely aim at enabling more comprehensive service search and clustering. Thus, in this paper, we describe our approach of combining the strengths of both distinct approaches to modeling Semantic Web Services – “lightweight” Linked Services and “heavyweight” SWS automation – into a coherent SWS framework. In addition, an implementation of our approach based on existing SWS tools together with a proof-of-concept prototype used within the EU project NoTube is presented

Web Services-Enhanced Agile Modeling and Integrating Business Processes

In a global business context with continuous changes, the enterprises have to enhance their operational efficiency, to react more quickly, to ensure the flexibility of their business processes, and to build new collaboration pathways with external partners. To achieve this goal, they must use e-business methods, mechanisms and techniques while capitalizing on the potential of new information and communication technologies. In this context, we propose a standards, model and Web services-based approach for modeling and integrating agile enterprise business processes. The purpose is to benefit from Web services characteristics to enhance the processes design and realize their dynamic integration. The choice of focusing on Web services is essentially justified by their broad adoption by enterprises as well as their capability to warranty interoperability between both intra and inter-enterprises systems. Thereby, we propose in this chapter a metamodel for describing business processes, and discuss their dynamic integration by addressing the Web services discovery issue. On the one hand, the proposed metamodel is in line with the W3C Web services standards, namely, WSDL, SAWSDL and WS-Policy. It considers the use of BPMN standard to describe the behavioral aspect of business processes and completes their design using UML diagrams describing their functional, non-functional and semantic aspects. On other hand, our approach for integrating processes is in line with BPEL standard recommended to orchestrate Web services. To realize executable business processes, this approach recommends the use of semantic matching and selection mechanisms in order to produce agile systems.Comment: 26 pages, 9 figures, Book chapte

Mobile Life: A Research Foundation for Mobile Services

The telecom and IT industry is now facing the challenge of a second IT-revolution, where the spread of mobile and ubiquitous services will have an even more profound effect on commercial and social life than the recent Internet revolution. Users will expect services that are unique and fully adapted for the mobile setting, which means that the roles of the operators will change, new business models will be required, and new methods for developing and marketing services have to be found. Most of all, we need technology and services that put people at core. The industry must prepare to design services for a sustainable web of work, leisure and ubiquitous technology we can call the mobile life. In this paper, we describe the main components of a research agenda for mobile services, which is carried out at the Mobile Life Center at Stockholm University. This research program takes a sustainable approach to research and development of mobile and ubiquitous services, by combining a strong theoretical foundation (embodied interaction), a welldefined methodology (user-centered design) and an important domain with large societal importance and commercial potential (mobile life). Eventually the center will create an experimental mobile services ecosystem, which will serve as an open arena where partners from academia and industry can develop our vision an abundant future marketplace for future mobile servíces

A Framework for QoS-aware Execution of Workflows over the Cloud

The Cloud Computing paradigm is providing system architects with a new powerful tool for building scalable applications. Clouds allow allocation of resources on a "pay-as-you-go" model, so that additional resources can be requested during peak loads and released after that. However, this flexibility asks for appropriate dynamic reconfiguration strategies. In this paper we describe SAVER (qoS-Aware workflows oVER the Cloud), a QoS-aware algorithm for executing workflows involving Web Services hosted in a Cloud environment. SAVER allows execution of arbitrary workflows subject to response time constraints. SAVER uses a passive monitor to identify workload fluctuations based on the observed system response time. The information collected by the monitor is used by a planner component to identify the minimum number of instances of each Web Service which should be allocated in order to satisfy the response time constraint. SAVER uses a simple Queueing Network (QN) model to identify the optimal resource allocation. Specifically, the QN model is used to identify bottlenecks, and predict the system performance as Cloud resources are allocated or released. The parameters used to evaluate the model are those collected by the monitor, which means that SAVER does not require any particular knowledge of the Web Services and workflows being executed. Our approach has been validated through numerical simulations, whose results are reported in this paper

A metadata service for service oriented architectures

Service oriented architectures provide a modern paradigm for web services allowing seamless interoperation among network applications and supporting a flexible approach to building large complex information systems. A number of industrial standards have emerged to exploit this paradigm with the development o f the J2E E and .N E T infrastructure platforms, communication protocol SOAP, d e scription language WSDL and orchestration languages BPEL, XLANG and WSCI. At the same time the Semantic Web enables automated use of ontologies to describe web services in a machine interpretable language. To enable process composition and large scale resource integration over heterogeneous sources a new research in itiative is needed. Current initiatives have identified the role of Peer-to-Peer networks and Service Oriented Architectures to enable large scale resource communication an d integration. However this approach neglects to identify or utilise the role of Semantic Web technologies to promote greater automation and reliability using service semantics, thus a new framework is required adopting Peer-to-Peer networks, Service Oriented Architectures and Semantic Web technologies. In this context, this thesis presents a management an d storage framework for a distributed service repository over a super peer network to facilitate process composition

Automated analysis of inter-parameter dependencies in web APIs

Web services often impose constraintsthat restrict the way in which two or more input parameters can be combined to form valid calls to the service, i.e. inter-parameter dependencies. Current web API specification languages like the OpenAPI Specification (OAS) pro vide no support for the formal description of such dependencies, making it hardly possible to interact with the services without human intervention. We propose specifying and automatically ana lyzing inter-parameter dependencies in web APIs. To this end, we propose a domain-specific language to describe these dependencies, a constraint programming-aided tool supporting their automated analysis, and an OAS extension integrating our approach and eas ing its adoption. Together, these contributions open a new range of possibilities in areas such as source code generation and testin