Markus Mathes

Flex-SwA: Flexible Exchange of Binary Data Based on SOAP Messages with Attachments

SOAP is the standard protocol for message exchange in Web service environments. As an XML-based protocol, SOAP is not suitable for the transmission of large amounts of binary data. This fact has been addressed by the SOAP messages with attachments specification, which regulates the transfer of a SOAP message together with an arbitrary number of binary attachments composed within a MIME multipart/related message. Although this leads to a reduction of transmission overhead, Web service communication using SOAP messages with attachments still lacks communication and processing flexibility. In this paper, we present a novel and more flexible way of handling attachments in SOAP-based Web service environments. In contrast to SOAP messages with attachments, our approach offers message forwarding without additional communication cost and demand-driven evaluation and transmission of binary data, thus providing the opportunity to save time by overlapping service execution and data transmission

WS-TemporalPolicy: A WS-Policy Extension for Describing Service Properties with Time Constraints

A Web service has several functional properties (e.g. its operations) and non-functional properties (e.g. quality of service and security parameters). Functional properties are usually static, whereas non-functional properties are often dynamic and thus vary over time. To describe properties with time constraints, the paper introduces WS-TemporalPolicy. WS-TemporalPolicy empowers a service developer to attach a validity period to the properties described in a WS-policy. The generation, validation, storage and retrieval, and deployment process of temporal policies is supported by the Temporal Policy Runtime Environment. Implementation issues and two use cases are presented to illustrate the use of temporal policies.

SOAP4PLC: Web Services for Programmable Logic Controllers

The use of service-oriented architectures based on web services in the manufacturing layer of industrial enterprises yields vertical integration and promises increased interoperability and flexibility. Unfortunately, two main obstacles complicate the use of web services in the manufacturing layer. First, the hardware/software used in this layer differs from the hardware/software used in other layers. Second, the manufacturing layer is maintained by automation engineers who typically are not familiar with web services. This paper presents the first SOAP engine for programmable logic controllers to advance the use of web services in the manufacturing layer. The engine offers a low memory footprint to respect the low computational power of programmable logic controllers and allows to export web services automatically without intervention of an automation engineer.

A Web Service Communication Policy for Describing Non-standard Application Requirements

Web services are not really suitable for implementing applications with non-standard communication requirements, such as e.g. applications with data streaming and/or realtime requirements, applications depending on the transfer of large files, and legacy applications with complex message exchange patterns. This paper presents a communication policy for Web services based on WS-Policy, which enables the description of real-time and data streaming requirements, of file transfers, and of protocols and clients used by legacy applications. It is used in addition to the WSDL description of a service, and thus complements the service description by exposing the protocols used by the applications for the various requirements. By investigating a video-on-demand application, several limits of Web service technologies and the benefits of using the communication policy to describe such requirements are illustrated.

DAVO: A Domain-Adaptable, Visual BPEL4WS Orchestrator

The Business Process Execution Language for Web Services (BPEL4WS) is the de facto standard for the composition of web services into complex, valued-added workflows in both industry and academia. Since the composition of web services into a workflow is challenging and error-prone, several graphical BPEL4WS workflow editors have been developed. These tools focus on the composition process and the visualization of workflows and mainly address the needs of web service experts.To increase the acceptance of BPEL4WS in new application domains, it is mandatory that non web service experts are also empowered to easily compose web services into a workflow. This paper presents the Domain-Adaptable Visual Orchestrator (DAVO), a graphical BPEL4WS workflow editor which offers a domain-adaptable data model and user interface. DAVO can be easily customized to domain needs and thus is suitable for non web service experts.

Towards a time-constrained web service infrastructure for industrial automation

This paper suggests to seamlessly adopt a service-oriented architecture based on Web services throughout an industrial enterprise as a standardized, homogeneous communication backbone, from the business layer down to the manufacturing layer. Since manufacturing processes typically have time constraints, especially real-time constraints, particular attention has to be paid to the description of such time constraints within a Web service and the timely execution of time-constrained Web services within the proposed infrastructure. Furthermore, an outline of the time-constrained services (TiCS) framework - a framework which empowers automation engineers to develop, deploy, publish, compose and invoke time-constrained services - and a prototypical implementation of two main components of the TiCS framework, namely the TiCS Wizards and the TiCS Real-time Repository, are presented.

SOAP4IPC: A Real-Time SOAP Engine for Industrial Automation

The adoption of service-oriented architectures based on web services in industrial automation promises increased interoperability and flexibility. However, industrial automation requires real-time processing, i.e. a task has to be processed within a specific deadline, which is a large obstacle for utilizing web services in this domain.The Time-Constrained Services (TiCS) framework meets the demands of industrial automation and empowers automation engineers to develop, deploy, publish, compose, and invoke time-constrained web services. This paper presents the TiCS real-time SOAP engine for industrial PCs called SOAP4IPC. It permits the execution of web services in real-time. The architecture of the SOAP4IPC engine, implementation details, and experimental results are discussed.

Java RMI versus .NET Remoting Architectural Comparison and Performance Evaluation

The implementation of distributed applications can be based on a multiplicity of technologies, e.g. plain sockets, Remote Procedure Call (RPC), Remote Method Invocation (RMI), Java Message Service (JMS), .NET Remoting, or Web Services. These technologies differ widely in complexity, interoperability, standardization, and ease of use. To achieve the highest efficiency, the use of plain sockets is advisable, whereas highest interoperability and standardization argue for Web Services. Real world applications requirements are a trade-off between efficiency, development costs, usability, reliability, interoperability, and so on. For example, a multimedia streaming application requires high performance to avoid delays, whereas Internet trading platforms depend on high interoperability, reliability and availability. Since Java RMI and .NET Remoting support fast development of highly efficient applications, many developers choose one of these technologies to realize their applications. Besides differences in design, the two technologies offer diverse performance characteristics. This paper has two main contributions: (1) a comparison of the design and architecture of Java RMI and .NET Remoting is presented, (2) an experimental performance analysis with respect to various aspects of both technologies is conducted.

Mapping Virtual Organizations in Grids to Peer-to-Peer Networks

Virtual organizations in Grid computing environments are arrangements of Grid participants into groups, where each participant may belong to different physical organizations. The combination of Grid computing and peer-to-peer technology causes problems in terms of forming, organizing, and managing virtual organizations in such networks. In this paper, a novel approach to map a Grid to a peer-to-peer network and to map each virtual organization to a group of peers, independent of a particular virtual organization software and peer-to-peer network, is presented. A prototypical implementation based on the Globus Toolkit 4 Grid middleware, the peer-to-peer framework Free Pastry and the virtual organization solutions GridShib/Shibboleth and the Virtual Organization Membership Service, is presented.

Orchestration of Time-Constrained BPEL4WS workflows

The adoption of service-oriented architectures based on Web services in industrial automation promises increased interoperability and flexibility. The orchestration of existing Web services to workflows is a challenging task which is complicated by the fact that manufacturing processes have time constraints, especially real-time constraints. This paper presents the time-constrained services (TiCS) Modeler which supports the assisted orchestration of BPEL4WS workflows with time constraints. The presented prototypical implementation is based on a formal derivation of the time constraints of a workflow.