No abstract

Cyber physical systems (CPS) react to changes in the environment and have become widely adopted in many domains. One key functionality to achieve this reactivity is the processing of event streams. To profit from this reactive behavior in serviceoriented architectures (SOA), event stream processing needs to be encapsulated in a service-like manner. We thus introduce the concept of event applets, in short Eventlets, to provide developers and architects alike with a generic and reusable component model for encapsulating event stream processing logic. Eventlets have a managed lifecycle and are activated automatically upon arrival of appropriate events. We introduce our distributed Eventlet middleware architecture and implementation based on industrystrength message-oriented middleware. Our evaluation shows that Eventlets simplify the development of reactive components and that they can compete with traditional event processing approaches in terms of performance. Eventlets enable easy distribution of event stream processing components and are a suitable foundation for scalable applications that combine SOA with CPS.

Abstract. Today's production processes are characterized by global supply chains, short lifecycles, and an increasing personalization of goods. To satisfy the demands for agility we must integrate the production with the logistics processes and knowledge about the underlying transportation services and infrastructure. This requires continuous monitoring and reacting to events. Service-oriented architectures have provided a platform for structuring services within and across enterprises. However, for an effective monitoring and timely reaction to emerging situations it is crucial to integrate event processing and service orientation. In this position paper we show how event processing and service orientation can be combined into an effective delivery platform for an integrated coordination of the flow of goods. We show how simple events, e.g. RFID tag detections or simple sensor readings, can be integrated into abstract events that are meaningful to invoke logistics services and improve the celerity of responses. We propose filtering, aggregating, and on-the-fly analysis of the continuous flow of events and make events persistent in an event warehouse for auditability and input to future planning processes.

The Internet of Things and Cyber-physical Systems provide enormous amounts of real-time data in form of streams of events. Businesses can benefit from the integration of this real-world data; new services can be provided to customers, or existing business processes can be improved. Events are a wellknown concept in business processes. However, there is no appropriate abstraction mechanism to encapsulate event stream processing in units that represent business functions in a coherent manner across the process modeling, process execution, and IT infrastructure layer. In this paper we present Event Stream Processing Units (SPUs) as such an abstraction mechanism. SPUs encapsulate application logic for event stream processing and enable a seamless transition between process models, executable process representations, and components at the IT layer. We derive requirements for SPUs and introduce a BPMN extension to model SPUs. We present a runtime infrastructure that executes SPUs and supports implicit invocation and completion semantics. We illustrate our approach using a logistics process as running example.

Implicit invocations are a popular mechanism for exchanging information between software components without binding these strongly. This decoupling is particularly important in distributed systems when interacting components are not known until runtime. In most realistic distributed systems though, components require some information about each other, be it only about their presence or their number. Runtime systems for implicit invocations-so-called publish/subscribe systems-are thus often combined with other systems providing such information.Given the variety of requirements for information about interacting components across applications, this paper proposes a generic augmentation of implicit invocations: rather than extending a given publish/subscribe API and system in order to convey a particular type of information across interacting components, we describe domain-specific joinpoints that can be used to advise application-level invocation routers-so-called brokers-used by publish/subscribe systems. This enables aggregation of application-specific information to and from components in a scalable manner.After presenting our domain-specific joinpoint model, we describe its implementation inside the REDS publish/subscribe middleware. The empirical evaluation of our approach shows that: (a) it outperforms external aggregation systems, by collecting and distributing information with a limited overhead; (b) the deployment of new functionalities has virtually no overhead, even if it occurs while the publish/subscribe system is running.