Steffen Heinzl

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.

A scalable service-oriented architecture for multimedia analysis, synthesis and consumption

Although Service-Oriented Architectures (SOAs) were not designed for multimedia processing, they speed up the development of distributed multimedia applications by allowing the composition or reconfiguration of existing services. For example, the Business Process Execution Language for Web Services (BPEL) is a powerful tool to orchestrate, model and execute workflows. However, due to its process-oriented approach, it is not directly applicable to data-intensive applications, such as those from the multimedia domain. In this paper, a comprehensive service-oriented infrastructure for multimedia applications is presented that (a) overcomes some drawbacks of BPEL for data-intensive applications and (b) provides tools that further ease the development and use of web services for a broad scope of multimedia applications covering video content analysis, audio analysis and synthesis and multimedia consumption. The proposed service-oriented infrastructure can be easily integrated into existing business processes by using BPEL. A dynamic allocation of cloud computing resources ensures the scalability of a multimedia application. To allow efficient and flexible data transfers in BPEL workflows, an implementation of the Flexible SOAP with Attachments (Flex-SwA) architecture is used that allows data transmission in conjunction with SOAP messages. The protocol requirements of services in the case of real-time, streaming or file transfer can be described by a communication policy. Three use cases of multimedia applications are evaluated.

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.

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.

Efficient data transmission in service workflows for distributed video content analysis

Workflows of web services orchestrated by the Business Process Execution Language (BPEL) have been successfully used in many business applications. Although these technologies were not originally designed for multimedia processing, they offer advantages to speed up the development of distributed multimedia analysis applications by allowing the composition or reconfiguration of existing services. However, in the case of service-oriented distributed video content analysis, a huge amount of binary data has to be transferred between different services. As a consequence, service orchestration based on BPEL leads to a performance bottleneck due to indirect message and data transport: the workflow engine receives results (which are potentially very large) from finished services and passes them to a subsequent service. In this paper, we present two novel approaches based on our previously developed Flex-SwA framework to model the binary data transmission between services in BPEL workflows. The proposed approaches circumvent the performance bottleneck at the orchestrating engine and provide efficient possibilities to transfer large data amounts as well as large data units. The first approach models the data flow in BPEL; the services exchange data directly. The second approach models the data flow outside of the BPEL engine and shifts it completely to the Flex-SwA framework. Experimental results for a video analysis workflow demonstrate the advantages of the proposed approaches.

MIRO: a mashup editor leveraging web, Grid and Cloud services

High performance computing resources are currently mainly used by computer scientists or domain experts. With the upcoming Cloud computing infrastructures and the vast amount of data available in the World Wide Web, such computing resources become interesting for end users who want to develop their own computationally demanding applications. In this paper, a service-enabled mashup editor called MIRO is presented to assist end users in the task of developing distributed applications utilizing high performance computing resources. MIRO allows the combination of popular web applications with Grid and Cloud services. The separation of the view into a user and developer view allows both the user and the developer to easily work with the editor. Two use cases are presented to show how Flickr and YouTube search can be combined with multimedia analysis services.

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.

Exposing validity periods of prices for resource consumption to web service users via temporal policies

Web services usually have functional as well as non-functional properties. Functional properties, such as the WSDL description, are usually static, whereas non-functional properties are often dynamic and thus vary over time. One of these non-functional properties are prices for using a web service or the resources it consumes. It is desirable to dynamically set prices depending on criteria such as the time of day or usage patterns and to expose pricing information in several ways. In this paper, we introduce an extended version of our previously proposed temporal policy language to handle these requirements. The extension provides the possibility of adding the exposition of validity periods to service users by weaving an attribute from the temporal policy namespace to WS-Policies. Furthermore, a schema for temporal policies and a state diagram are introduced. A use case from the area of pricing high performance computing resources is presented to demonstrate that exposing validity periods to service users enables them to automatically estimate how long they can use computing resources for a given price.