Sonja Zaplata

Mobile process description and execution

Mobile devices are increasingly aware of their respective locations and vicinity and tend to communicate rather loosely with each other; therefore asynchronous communication paradigms are used predominately so far for corresponding mobile applications. However, while such communication mechanisms are suitable for simple activities, they may become insufficient for more complex tasks which consist of longer sequences of related activities tied together in application-oriented processes. This is of particular importance if the resulting operating sequence spans several mobile devices in frequently changing vicinities. Therefore, the work presented here provides a concept for integrating explicit support for such mobile processes into mobile system infrastructures and for distributing their execution over different nodes in the network. For this purpose, a corresponding middleware platform (extension) for context-aware mobile applications is proposed. It supports such migrating processes and helps to execute them under the restrictions typically imposed by realistic mobile applications. In particular, this paper proposes a corresponding process description language and an execution model for mobile and distributed (business) processes in the context of the project DEMAC (Distributed Environment for Mobility-Aware Computing).

Mobile Processes: Enhancing Cooperation in Distributed Mobile Environments

Currently, context awareness is one of the main trends in distributed mobile computing environments. Against this background, the demand for more complex – and additionally long-term – mobile applications increases continuously. Nevertheless, most current available mobile applications – as well as their supporting middleware platforms – are still relatively monolithic and closed systems, concentrating on only short-term activities. As a consequence, most present appliances are still restricted to rather simple tasks and are therefore rather insufficient for more complex ones which consist of sequences of related long-term activities tied together in respective application-oriented processes. In order to overcome the resource and capability restrictions of mobile environments, such application processes may profit from, e.g., cooperation between devices in the mobile vicinity – a fact which is hardly supported by existing systems. Therefore, this paper introduces a concept for integrating explicit support for mobile processes into mobile system infrastructures and for distributing their execution over different nodes in the network. Additionally, a corresponding middleware platform for context-aware and cooperative mobile applications is proposed. This framework has been designed and realized in the context of project DEMAC (Distributed Environment for Mobility-Aware Computing) which supports such migrating processes and helps to execute them under the restrictions imposed by realistic mobile applications. In particular, this paper proposes a corresponding process description language and an execution model for such mobile (business) processes.

Enabling Context-Based Cooperation: A Generic Context Model and Management System

In order to realise complex service-based applications on system platforms for context-aware ubiquitous computing environments, mobile processes have been introduced to support cooperation among (mobile) devices by exchanging and executing arbitrary (business) processes. In such a view, middleware platforms that support the execution and migration of mostly a priori unknown processes need a generic and also application-independent context system. Accordingly, this paper presents an approach for a generic context model and management platform to support such context-based cooperation as currently developed and used in the project DEMAC (Distributed Environment for Mobility-Aware Computing).

Towards runtime migration of WS-BPEL processes

The decentralized execution of business process instances is a promising approach for enabling flexible reactions to contextual changes at runtime. Most current approaches address such process distribution by physical fragmentation of processes and by dynamic assignment of resulting static process parts to different business partners. In order to enable a more dynamic segmentation of such responsibilities at runtime, this paper proposes to use process runtime migration as a means of logical process fragmentation. Accordingly, the paper presents a general migration metadata model and a corresponding basic privacy and security mechanism for enhancing existing process models with the ability for runtime migration while respecting the intensions and privacy requirements of both process modelers and initiators. The approach is conceptually evaluated by applying it to WS-BPEL processes and comparing the results to the general concept of process fragmentation.

Structured context prediction: a generic approach

Context-aware applications and middleware platforms are evolving into major driving factors for pervasive systems. The ability to also make accurate assumptions about future contexts further enables such systems to proactively adapt to upcoming situations. However, the provision of a reusable system component to facilitate the development of such future-context-aware applications is still challenging - as it requires to be generic but, at the same time, as efficient and accurate as possible. To address these requirements, this paper presents the approach of Structured Context Prediction which constitutes a framework to facilitate the application of existing prediction methods. It allows application developers to integrate domain-specific knowledge by creating a customized prediction model at design time and to select, implement and combine prediction methods for the intended purpose. Feasibility is evaluated by applying a prototype system component to two mobile application scenarios, showing that both high accuracy and efficiency are possible.

Towards mobile process as a service

Process as a Service (PaaS) addresses modeling, execution and management of business processes without running extensive and costly process management software. Such a flexible outsourcing strategy is especially advantageous in the context of mobile devices and services which are increasingly relevant for contemporary business activities. Based on the concept of context-based cooperation, this paper proposes a PaaS solution for mobile participants which enables them to share existing local and remote resources and to utilize PaaS functionality of cooperating providers in a user-defined way. The approach is realized and evaluated by an extended prototype implementation of the DEMAC (Distributed Environment for Mobility Aware Computing) platform.

Realizing Mobile Web Services for Dynamic Applications

Use of web services also on mobile devices becomes increasingly relevant. However, realizing such mobile web services based on the standard protocol stack is often inappropriate for resource-restricted mobile devices in dynamic networks. On the other hand, using specialized alternative protocols restricts compatibility with traditional service applications. Thus, existing approaches often do not allow to integrate heterogeneous service instances dynamically, as it is, e.g., required for executing mobile service-based business processes.

Designing future-context-aware dynamic applications with structured context prediction

Middleware support for advanced pervasive applications includes dealing with heterogeneous systems and dynamic changes of execution environments. If applications are context aware, they are able to detect such changes at runtime and react to them accordingly. Furthermore, they can also proactively adapt to upcoming situations by making accurate assumptions about future contexts. However, the design of reusable middleware support for such future‐context‐aware applications is still challenging as a supporting prediction system has to be generic, but at the same time has to provide potential for high accuracy and efficiency.

Migratability of BPMN 2.0 process instances

The migration of running process instances allows for a dynamic distribution of individual business processes at runtime. However, a widely-used standardized process description language and an agreed format for the exchange of process instance data are vital for the applicability of such concept. The newly evolved standard of the Business Process Model and Notation (BPMN 2.0) is currently gaining acceptance in many organizations and is supported by a growing number of process engines. In order to leverage BPMN for the dynamic distribution of business processes, this paper presents an analysis on the migratability of running BPMN process instances. The results include a mapping of BPMN 2.0 control flow elements to an existing migration model and a novel migration concept for process instances which contain BPMN-specific elements such as events, pools and user tasks. In addition, the effort for extending a BPMN process engine is evaluated by a prototype implementation based on the open source Activiti process engine.

Towards NFC-Aware Process Execution for Dynamic Environments

A flexible execution of business processes requires to deal with dynamic environments and to adapt to specific situations detected at runtime. However, flex- ibility needs to be restricted in a reasonable way which fits the requirements of the process initiator. An important aspect is the specification of user-defined constraints with respect to the non-functional characteristics (NFCs) of the execution. However, most existing approaches for such descriptions and corresponding service selection mechanisms are computationally complex and thus hinder a flexible runtime dis- tribution of the process including resource-restricted clients such as, e.g., mobile devices. This paper addresses the problem of NFC-aware process execution in such dynamic environments. Therefore, the paper presents an NFC meta-model and a correspond- ing language to support process modelers in expressing their non-functional require- ments in a way which facilitates runtime decomposition and to dynamically derive local NFC specifications from remaining global requirements on process level by more simple heuristic approaches. Based on that, an initial algorithm is introduced in order to evaluate NFCs during runtime.