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Beschreibung:
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 ...