On the application of the service-oriented architectural style to heterogeneous application landscapes

This thesis investigates the application of the service-oriented architectural style in the context of industrial enterprises. This style provides a commonly perceived paradigm to organize distributed software systems. However, beyond the attention this style attracts, little description exists on what differentiates service orientation from already more mature styles, such as component orientation. This dissertation argues that the service-oriented style is an approach that centralizes control over distributed functionality that is provided by the application systems of an organization. This means that service orientation is a paradigm for application integration. Moreover, we argue that it is not possible to fully formalize the inherent principles of service orientation as part of an architectural style description. In fact, soft design principles are a differentiator of this style. These principles, however, are rarely implied in the context of industrial enterprises. This is why we analyze how such design principles could be objectively described and what attention should be paid to them. This analysis is performed by categorizing the potential benefits of this style and assigning the respective principles to the identified benefits. Subsequently, a reference architecture is defined on the basis of these findings. This architecture focuses on structuring service-oriented applications — so-called composite applications. In order to apply the defined reference architecture in the context of actual projects, we describe a design methodology for composite applications. This design methodology focuses on predominantly using business processes to design various types of services and their interconnections as they are described by the reference architecture. To achieve this, a service design algorithm is included that derives services for business processes by incorporating the results of a statistical analysis of service design principles. The deliverable of this methodology is the platform-independent design of a composite application that incorporates the restrictions of the application landscape in which a composite will be deployed. To allow the realization of composite applications, we informally map the platform-independent reference architecture to a platform that is widely used in industrial enterprises. This mapping is, together with the design methodology and the reference architecture, applied to an industry-scale use case. This way the applicability of the concepts is demonstrated.