TY - JOUR A1 - Mathes, Markus A1 - Stoidner, Christoph A1 - Schwarzkopf, Roland A1 - Heinzl, Steffen A1 - Dörnemann, Tim A1 - Dohmann, Helmut A1 - Freisleben, Bernd T1 - Time-constrained services: a framework for using real-time web services in industrial automation JF - Service Oriented Computing and Applications N2 - The use of web services in industrial automation, e.g. in fully automated production processes like car manufacturing, promises simplified interaction among the manufacturing devices due to standardized protocols and increased flexibility with respect to process implementation and reengineering. Moreover, the adoption of web services as a seamless communication backbone within the overall industrial enterprise has additional benefits, such as simplified interaction with suppliers and customers (i.e. horizontal integration) and avoidance of a break in the communication paradigm within the enterprise (i.e. vertical integration). The Time-Constrained Services (TiCS) framework is a development and execution environment that empowers automation engineers to develop, deploy, publish, compose, and invoke time-constrained web services. TiCS consists of four functional layers—tool support layer, real-time infrastructural layer, real-time service layer, and hardware layer—which contain several components to meet the demands of a web service based automation infrastructure. This article gives an overview of the TiCS framework. More precisely, the general design considerations and an architectural blueprint of the TiCS framework are presented. Subsequently, selected key components of the TiCS framework are discussed in detail: the SOAP4PLC engine for equipping programmable logic controllers with a web service interface, the SOAP4IPC engine for processing web services in real-time on industrial PCs, the WS-TemporalPolicy language for describing time constraints, and the TiCS Modeler for composing time-constrained web services into a time-constrained BPEL4WS workflow. Y1 - 2009 UR - https://link.springer.com/article/10.1007/s11761-009-0050-y VL - 3 SP - 239 EP - 262 PB - Springer London ER - TY - CHAP A1 - Mathes, Markus A1 - Schwarzkopf, Roland A1 - Dörnemann, Tim A1 - Heinzl, Steffen A1 - Freisleben, Bernd T1 - Composition of Time-Constrained BPEL4WS Workflows Using the TiCS Modeler T2 - 13th IFAC Symposium on Information Control Problems in Manufacturing N2 - The adoption of service-oriented architectures based on web services in industrial automation promises increased interoperability and exibility. Since the development and deployment of web services requires in-depth programming knowledge, adequate tools to ease the work of automation engineers are required. In particular, the orchestration of existing web services to workflows is a challenging task that is complicated by the fact that manufacturing processes have time constraints, especially real-time constraints. This paper presents the Time-Constrained Services (TiCS) Modeler that supports the assisted orchestration of BPEL4WS workflows with time constraints. Y1 - 2009 U6 - https://doi.org/https://doi.org/10.3182/20090603-3-RU-2001.0104 VL - 42 IS - 4 SP - 888 EP - 893 PB - Elsevier ER - TY - CHAP A1 - Stoidner, Christoph A1 - Mathes, Markus A1 - Freisleben, Bernd T1 - Sequence-Controlled Web Services for Programmable Logic Controllers T2 - 13th IFAC Symposium on Information Control Problems in Manufacturing N2 - The use of service-oriented architectures based on web services in the manufacturing layer of industrial enterprises enables vertical integration and promises increased interoperability. Unfortunately, the differing execution patterns—cyclic execution on programmable logic controllers vs. on-demand execution on industrial PCs—complicate the use of web services in the manufacturing layer. This paper introduces sequence-controlled web services that permit to easily export a control module as a web service. An automation engineer can use familiar IEC 61131-3 programming languages to implement the control application and subsequently can export selected modules as web services. Y1 - 2009 U6 - https://doi.org/https://doi.org/10.3182/20090603-3-RU-2001.0128 VL - 42 IS - 2 SP - 396 EP - 401 PB - Elsevier ER - TY - CHAP A1 - Dörnemann, Tim A1 - Mathes, Markus A1 - Schwarzkopf, Roland A1 - Juhnke, Ernst A1 - Freisleben, Bernd T1 - DAVO: A Domain-Adaptable, Visual BPEL4WS Orchestrator T2 - Proceedings of the 23rd IEEE International Conference on Advanced Information Networking and Applications N2 - 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. Y1 - 2009 U6 - https://doi.org/10.1109/AINA.2009.78 SP - 121 EP - 128 PB - IEEE Computer Society Press ER - TY - CHAP A1 - Heinzl, Steffen A1 - Mathes, Markus A1 - Stadelmann, Thilo A1 - Seiler, Dominik A1 - Diegelmann, Marcel A1 - Dohmann, Helmut A1 - Freisleben, Bernd T1 - The Web Service Browser: Automatic Client Generation and Efficient Data Transfer for Web Services T2 - Proceedings of the 7th IEEE International Conference on Web Services N2 - Web services are supported by almost all major software vendors, but nevertheless there is still a certain barrier that prevents a broader user community to actually use them. The barrier is the lack of appropriate clients offered in conjunction with the services. This paper presents a Web Service Browser that automatically generates a dynamic user interface when the user browses to the location of the service description and additionally handles the invocation of the service. To ease the use of the service, the browser takes care of data management by using an implementation of the Flex-SwA architecture. Results are presented to the user in a human-readable manner. When the result contains multimedia data, an audio or video player is used to present the result. Use cases demonstrate the benefits of the browser. With the Web Service Browser, web services simply become a usable component offered in the WWW. Y1 - 2009 U6 - https://doi.org/10.1109/ICWS.2009.22 SP - 743 EP - 750 PB - IEEE Computer Society Press ER - TY - CHAP A1 - Mathes, Markus A1 - Stoidner, Christoph A1 - Heinzl, Steffen A1 - Freisleben, Bernd T1 - SOAP4PLC: Web Services for Programmable Logic Controllers T2 - 17th Euromicro International Conference on Parallel, Distributed, and Network-Based Processing N2 - 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. Y1 - 2009 U6 - https://doi.org/https://doi.org/10.1109/PDP.2009.42 SP - 210 EP - 219 PB - IEEE Computer Society Press ER - TY - CHAP A1 - Mathes, Markus A1 - Gärtner, Jochen A1 - Dohmann, Helmut A1 - Freisleben, Bernd T1 - SOAP4IPC: A Real-Time SOAP Engine for Industrial Automation T2 - 17th Euromicro International Conference on Parallel, Distributed, and Network-Based Processing N2 - 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. Y1 - 2009 U6 - https://doi.org/https://doi.org/10.1109/PDP.2009.21 SP - 220 EP - 226 PB - IEEE Computer Society Press ER - TY - JOUR A1 - Mathes, Markus A1 - Heinzl, Steffen A1 - Schwarzkopf, Roland A1 - Freisleben, Bernd ED - Müller, P. ED - Neumair, B. ED - Rodosek, G. D. T1 - F&L-Grid: Eine generische Backup und Recovery Infrastruktur für das D-Grid JF - 2. DFN-Forum Kommunikationstechnologien N2 - Grid Computing wird oftmals zur Durchführung zeitintensiver Experimente, die eine enorme Menge an Daten produzieren, verwendet. Da existierende Backup und Recovery Lösungen basierend auf GridFTP oder RFT detaillierte technische Kenntnisse bezüglich Konfiguration und Nutzung erfordern, sind diese nicht unbedingt für alle Anwender geeignet. Viele Wissenschaftler bevorzugen eine möglichst einfache und bedienungsfreundliche Lösung, um ihre experimentellen Ergebnisse zu sichern. Das F&L-Grid Projekt, welches die Entwicklung eines Grids für Forschung und Lehre beabsichtigt, ist ein Teil des D-Grid. Hauptziel von F&L-Grid ist der Entwurf und die Entwicklung einer generischen Backup und Recovery Infrastruktur für beliebige Grid-Umgebungen. Dieser Beitrag diskutiert den aktuellen Projektstatus von F&LGrid und skizziert den Entwurf und die Implementierung der generischen Backup und Recovery Infrastruktur. Y1 - 2009 SP - 55 EP - 67 PB - Gesellschaft für Informatik e.V. CY - Bonn ER - TY - CHAP A1 - Mathes, Markus A1 - Heinzl, Steffen A1 - Freisleben, Bernd T1 - Towards a Generic Backup and Recovery Infrastructure for the German D-Grid Initiative T2 - Tagungsband der ITG/GI-Fachtagung Kommunikation in Verteilten Systemen (KiVS) N2 - Grid computing is often used for conducting time-consuming experiments that produce large amounts of data. Since existing backup and recovery solutions based on GridFTP or RFT require in-depth knowledge, they are not suited for scientists who are not Grid computing experts. Most scientists prefer an easy to use solution to back up and recover their experimental results. The F&L-Grid project (a Grid providing services for research and education) is part of the German Grid Initiative (D-Grid) and is aimed at the design and development of the first generic backup and recovery infrastructure suitable for arbitrary Grid environments. This paper presents the current status of the ongoing F&L-Grid project and outlines the generic backup and recovery infrastructure in detail. Y1 - 2009 UR - https://link.springer.com/content/pdf/10.1007/978-3-540-92666-5.pdf?pdf=button SP - 229 EP - 240 PB - Springer ER - TY - CHAP A1 - Heinzl, Steffen A1 - Mathes, Markus A1 - Freisleben, Bernd T1 - The Grid Browser: Improving Usability in Service-Oriented Grids by Automatically Generating Clients and Handling Data Transfers T2 - Proceedings of the 4th IEEE International Conference on e-Sciencee N2 - This paper presents a grid browser as a familiar environment for accessing a service-oriented grid. To relieve the service developer from developing a graphical user interface and a grid service client, and to relieve the service provider from installing and maintaining a grid portal, the proposed grid browser can be used instead of a grid portal. A grid browser is a Web browser that renders WSDL files similar to HTML files. Surfing to the location of the WSDL description of a grid service results in the automatic generation of a graphical frontend in the grid browser which a user can easily fill out to invoke a service or submit a job. Furthermore, data transfers are integrated into the grid browser by integrating an implementation of the Flex-SwA architecture, such that data transmission and service invocation can be done efficiently in a single step. An implementation of the proposed grid browser to improve the usability of a service-oriented grid is presented. A use case points out the advantages of the grid browser. Y1 - 2008 U6 - https://doi.org/10.1109/eScience.2008.19 SP - 269 EP - 276 PB - IEEE Computer Society Press ER - TY - CHAP A1 - Mathes, Markus A1 - Heinzl, Steffen A1 - Freisleben, Bernd T1 - Towards a time-constrained web service infrastructure for industrial automation T2 - Proceedings of the 13th IEEE International Conference on Emerging Technologies and Factory Automation (ETFA) N2 - 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. Y1 - 2008 U6 - https://doi.org/10.1109/ETFA.2008.4638496 SP - 846 EP - 853 PB - IEEE Computer Society Press ER - TY - CHAP A1 - Mathes, Markus A1 - Schwarzkopf, Roland A1 - Dörnemann, Tim A1 - Heinzl, Steffen A1 - Freisleben, Bernd T1 - Orchestration of Time-Constrained BPEL4WS workflows T2 - Proceedings of the 13th IEEE International Conference on Emerging Technologies and Factory Automation (ETFA) N2 - 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. Y1 - 2008 U6 - https://doi.org/10.1109/ETFA.2008.4638349 SP - 1 EP - 4 PB - IEEE Computer Society Press ER - TY - CHAP A1 - Mathes, Markus A1 - Heinzl, Steffen A1 - Freisleben, Bernd T1 - WS-TemporalPolicy: A WS-Policy Extension for Describing Service Properties with Time Constraints T2 - 32nd Annual IEEE International Computer Software and Applications Conference N2 - 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. Y1 - 2008 U6 - https://doi.org/10.1109/COMPSAC.2008.105 SP - 1180 EP - 1186 PB - IEEE Computer Society Press ER - TY - CHAP A1 - Heinzl, Steffen A1 - Mathes, Markus A1 - Freisleben, Bernd T1 - A Web Service Communication Policy for Describing Non-standard Application Requirements T2 - Proceedings of the 8th IEEE/IPSJ Symposium on Applications and the Internet (SAINT) N2 - 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. Y1 - 2008 U6 - https://doi.org/10.1109/SAINT.2008.14 SP - 40 EP - 47 PB - IEEE Computer Society Press ER - TY - CHAP A1 - Schwarzkopf, Roland A1 - Mathes, Markus A1 - Heinzl, Steffen A1 - Freisleben, Bernd A1 - Dohmann, Helmut T1 - Java RMI versus .NET Remoting Architectural Comparison and Performance Evaluation T2 - Proceedings of the 7th International Conference on Networking (ICN) N2 - 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. Y1 - 2008 U6 - https://doi.org/10.1109/ICN.2008.88 SP - 398 EP - 407 PB - IEEE Computer Society Press ER - TY - CHAP A1 - Dörnemann, Tim A1 - Heinzl, Steffen A1 - Dörnemann, Kay A1 - Mathes, Markus A1 - Smith, Matthew A1 - Freisleben, Bernd T1 - Secure Grid Service Engineering for Industrial Optimization T2 - Proceedings of the 7th International Conference on Optimization: Techniques and Applications (ICOTA) Y1 - 2007 SP - 371 EP - 372 ER - TY - BOOK A1 - Mathes, Markus T1 - Time-Constrained Web Services for Industrial Automation N2 - Service-oriented architectures based on web services have become the de facto standard for the design and implementation of distributed applications. Due to their standardization, web services are widely adopted for inter-organizational communication, but their use for intra-organizational communication is challenging, especially within enterprises of the manufacturing domain. Business processes within an industrial enterprise have to satisfy predefined time constraints. More precisely, the manufacturing process has to guarantee real-time, i.e. predefined deadlines have to be kept. Todays industrial enterprises use specialized hard- and software at the manufacturing layer - industrial PCs (IPCs) and programmable logic controllers (PLCs) - that run under vendor-specific operating systems and are implemented using vendor-specific tools. This mixture of technologies of different vendors leads to numerous breaks in the communication paradigm. The interconnection of these technologies results in additional costs and is often quite error-prone. This thesis investigates the seamless use of web services as a homogeneous communication backbone throughout the overall industrial enterprise with a focus on the manufacturing layer. The common layered organization of an industrial enterprise - consisting of the business layer, the intermediate layer, and the manufacturing layer - is avoided by using web services as the communication backbone. The need for real-time makes the use of web services in industrial automation challenging. Web service standards (e.g. SOAP for the invocation and WSDL for the description of web services) and technologies (e.g. available SOAP engines) have emerged from the Internet domain where processing is based on a best-effort basis (time constraints are of little or no interest). The Time-Constrained Services (TiCS) framework presented in this thesis is a technical foundation for using web services in time-constrained environments with a specific focus on industrial automation. TiCS is a tool suite for the development, deployment, publication, composition, and execution of web services with time constraints, especially real-time constraints. TiCS consists of several components to ease the entire development process for automation engineers who are normally not familiar with web service technologies. The main components of the TiCS framework can be distinguished according to their functionality: - permit access to the manufacturing layer using web services - permit the composition of several web services to a value-added workflow that represents a production process - offer a mechanism to describe the time constraints of web services and workflows - permit the efficient transmission of binary web service parameters To access the manufacturing layer using web services, the TiCS framework offers a real-time SOAP engine for IPCs called SOAP4IPC and for PLCs called SOAP4PLC. Both engines permit an evolutionary change to a web service based communication backbone, since existing hardware can be used further. Most real-world production processes consist of several steps. Due to this reason, it is necessary to combine web services to a multi-step workflow. The TiCS Modeler supports an automation engineer to define such workflows with regard to the required time constraints. The WS-TemporalPolicy language permits the description of time constraints for web services and entire workflows. Since time constraints may vary over time, e.g. compare processing during peak time and off-peak time, WS-TemporalPolicy permits the definition of a validity period for time constraints. The protocol predominantly used for the invocation of web services is SOAP. Since SOAP is based on XML, it is necessary to encode binary parameters, resulting in a remarkable overhead. For an efficient parameter transmission - a fundamental prerequisite to process a web service within a given deadline - the TiCS framework contains a component called Flex-SwA. Despite the fact that the technologies developed in this thesis focus on industrial automation, they can also be used in related research areas where web services are used as the communication technology. Y1 - 2009 U6 - https://doi.org/10.17192/z2009.0466 ER - TY - CHAP A1 - Heinzl, Steffen A1 - Mathes, Markus A1 - Friese, Thomas A1 - Smith, Matthew A1 - Freisleben, Bernd T1 - Flex-SwA: Flexible Exchange of Binary Data Based on SOAP Messages with Attachments T2 - 2006 IEEE International Conference on Web Services (ICWS'06) N2 - 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 Y1 - 2006 U6 - https://doi.org/10.1109/ICWS.2006.65 SP - 3 EP - 10 PB - IEEE Computer Society Press ER - TY - CHAP A1 - Mathes, Markus A1 - Heinzl, Steffen A1 - Friese, Thomas A1 - Freisleben, Bernd T1 - Enabling Post-Invocation Parameter Transmission in Service-Oriented Environments T2 - International conference on Networking and Services (ICNS'06) N2 - This paper addresses two drawbacks associated with using SOAP RPC to invoke services in service-oriented environments. First, overlapping of parameter production, parameter transmission and service execution is not possible, since all parameters of a service call have to exist prior to service invocation; until all parameters are available, a service caller has to defer service invocation. Second, the XML format of SOAP is not suitable to transfer large binary parameters, because encoding consumes a considerable amount of time. In this paper, a new approach to invoke Web services is presented, which enables post-invocation parameter transmission and efficient transmission of binary parameters, thus enabling the overlapping of parameter production, parameter transmission and service execution to reduce the overall processing time. To realize post-invocation parameter transmission, an extension of WSDL is proposed. It is shown how post-invocation parameter transmission enables the efficient implementation of stream-based production/consumption of parameters and pipelining. Furthermore, measurement results are presented demonstrating a noticeable performance gain Y1 - 2006 U6 - https://doi.org/10.1109/ICNS.2006.44 SP - 55 EP - 62 PB - IEEE Computer Society Press ER - TY - JOUR A1 - Heidinger, Florian A1 - Mathes, Markus A1 - Dohmann, Helmut T1 - Java Message Service (JMS) – Einsatz in der Industrieautomation JF - Automatisierungstechnische Praxis Y1 - 2004 IS - 5 SP - 61 EP - 70 PB - Oldenbourg ER - TY - CHAP A1 - Heidinger, Florian A1 - Mathes, Markus A1 - Dohmann, Helmut T1 - Werkzeug zur Visualisierung und Administration von Kommunikationsbeziehungen in nachrichtenorientierter Middleware T2 - CeBIT 2004 Y1 - 2004 ER - TY - BOOK A1 - Heinzl, Steffen A1 - Mathes, Markus T1 - Middleware in Java BT - Leitfaden zum Entwurf verteilter Anwendungen — Implementierung von verteilten Systemen über JMS — Verteilte Objekte über RMI und CORBA T3 - IT-Professional N2 - Dieses Buch vermittelt beispielhaft das notwendige Know-how zum Entwurf und zur Entwicklung verteilter Anwendungen. Die Umsetzung erfolgt mittels der relevanten Middleware-Technologien in Java. Die Darstellung erfolgt nachvollziehbar anhand praxisnaher Beispiele, Aufgaben helfen das Gelernte aktiv einzuüben. Der Quellcode der vorgestellten Programme und Präsentationen zur Unterstützung von Dozenten und Studenten werden zum Download angeboten. Als besonderer Service für Dozenten werden auch die Lösungen zu den Aufgaben bereitgestellt. Y1 - 2005 SN - 978-3-528-05912-5 U6 - https://doi.org/10.1007/978-3-322-80262-0 PB - Vieweg+Teubner Verlag CY - Wiesbaden ER -