Enterprise application systems rarely live in isolation as creating a single huge application that runs a complete business is almost impossible. Thus, enterprises typically run hundreds or even thousands of different application systems. Because most of these application systems typically need to work together to support common business processes and to share data across application systems, these application systems need to be integrated. Enterprise application integration needs to provide efficient, reliable and secure data exchange between multiple enterprise applications.

An important aspect of application integration is to keep the integrated application system inde-pendent. This is important in order to enable the different application systems to evolve without affecting each other and thus making the overall solution more flexible and tolerant to changes. This is often referred to as Loose Coupling.

Because integrating enterprise applications is a challenging topic some frequently recurring prob-lems and their solution has been described in form of patterns. Patterns are a technique to docu-ment expert knowledge and experience. The book “Enterprise Integration Patterns” by Gregor Hohpe and Bobby Woolf [HW03] describes a collection of patterns, residing in the domain of en-terprise application integration using messaging.

With companies starting to shift more and more from applications run on-premise to applications delivered in a Software as a Service (SaaS) delivery model, new integration challenges arise as these applications also need to be integrated with each other and with existing applications run on-premise. To tackle the integration challenges of both, software delivered as SaaS and software run on-premise, [SML08] proposes to offer enterprise integration patterns in a SaaS business model. Offering enterprise integration patterns as SaaS has the advantage of liberating companies from having to setup and maintain a complex integration infrastructure.

The main objective of this work is to analyze how these patterns can be delivered in the SaaS busi-ness model and how they can be connected to form a complete integration scenario.