Horst Pichler

Personal schedules for workflow systems

Personal schedules allow workflow participants to improve their performance of activity executions. Participants are no longer surprised by the entries in their work-lists but receive advance information about (potential) future activity assignments, allowing better possibilities for work-planning. The personal schedule system is based on a probabilistic workflow time management system using duration histograms. A personal schedule collects future activity assignments together with their probability and their timing requirements and allows to analyze the workload of a participant and to support the scheduling of activities with the goal of reduced turn-around times and reduced number of violations of temporal constraints.

Duration Histograms for Workflow Systems

Web-based interorganizational workflows need efficient time management. Variations of activity durations and branching distributions on or-split nodes make it necessary that we treat time management in workflows in a probabilistic way. We introduce the notion of duration histograms for capturing the available temporal information about workflow execution, define the necessary operations for computing timed execution plans for workflows and discuss the application of this new concepts for workflow design as well as time aware workflow execution management.

Transforming Workflow Graphs

Workflow management systems are very useful for integrating separately developed application systems by controlling flows of execution. For various purposes (e.g. distribution of activities, workflow evolution, time calculation, etc.) it is necessary to change the representation of a workflow, the structure of a workflow graph without changing it’s semantics. We provide an equivalence definition of workflow graphs and introduce a set of basic transformation operations defined on workflow graphs which keep the semantics. We show how these basic operations can be combined to achieve complex transformations and briefly describe a prototypical transformation tool.

Composing Time-Aware Web Service Orchestrations

Workflow time management deals with the calculation of temporal thresholds for process activities, which allows forecasts about looming deadline violations. We present a novel approach to transform a web service orchestration into a time-aware orchestration, that contains temporal assessment and intervention logic. During process execution intervention strategies are triggered pro-actively to speed up a late process and to avoid upcoming violations of temporal constraints.

Probabilistic calculation of execution intervals for workflows

The comprehensive treatment of time and time constraints is crucial in designing and managing business processes. Process managers need tools that help them predict execution durations, anticipate time problems, pro-actively avoid time constraint violations, and make decisions about the relative process priorities and timing constraints when significant or unexpected delays occur. Variations of activity durations and branching decisions at run-time make it necessary that we treat time management in workflows in a probabilistic way. Therefore we introduce the notion of probabilistic time management and discuss the application of this new concept for workflow design as well as time aware, predictive and proactive workflow execution management.

View-based interorganizational workflows

We propose a new architecture for modeling and enacting of interorganizational business processes which captures both control flow and data flow aspects of web service orchestrations and choreographies. A major modeling concepts is a view mechanism to balance the problems of openness, privacy and coupling in cross-organization interactions. The view concept cares both for process abstraction and for data transformation between business partners. To cope with interoperability problems that arise from different data formats and internal schemas used by different choreography participants we support transformation of XML-based data types through our views. The approach allows a to enact interorganizational business processes in a fully distributed way without the need for any central coordinator.

Probabilistic Time Management of Choreographies

Temporal conformance of web service compositions guarantees the timely execution of service calls, decreases follow-up costs and increases QoS by avoiding deadline violations. Since it is impossible to make certain statements about the execution intervals of upcoming web service executions - mainly due to varying activity durations and hard-to-predict branching behavior - we propose a probabilistic approach to model flow structures and temporal information, and show how to validate the temporal conformance of web service compositions.

Avoidance of deadline-violations for inter-organizational business processes

Workflow time management allows the prediction of eventually arising deadline violations and enables proactive initiation of evasive actions. This saves time, avoids compensation tasks and therefore decreases costs. Current time management approaches assume that communication with external tasks, which are enacted by the process, is conducted in a blocking or synchronous manner. As inter-organizational processes frequently communicate in a non-blocking manner we examined basic asynchronous communication patterns and provided a mapping for each pattern in order to use it for time management purposes

Business Process Modelling and Workflow Design

Detailed knowledge about the structure and functionality of a business process within an enterprise is of utter importance for a thorough understanding of organizational sequences. This is a crucial requirement in business process management (BPM) and business process re-engineering (BPR), which cover the entire process lifecycle, from modeling and design, to execution, monitoring, and optimization. Throughout this lifecycle, process models are required to represent an enterprise’s processes, so that they can be documented, communicated, verified, simulated, analyzed, automated, evaluated, or improved. This chapter provides an overview of business process modeling and workflow design, discusses their commonalities and differences, explains how different process perspectives aremodeled, and gives an overview of several business process modeling related research topics.

An architecture for proactive timed web service compositions

Web Services-based business processes spread over the boundaries of companies, requiring the integration of customers, suppliers and partners to achieve inter-organizational business goals. According to organizational rules temporal constraints, like deadlines, must be defined for processes. Violation of these constraints usually results in increased cost and reduced quality of service. Advanced workflow time management approaches allow the prediction of eventually arising time constraint violations and enables proactive initiation of evasive ”self healing” actions. This saves time, avoids unnecessary task-compensations and therefor decreases costs. In this paper we present an architecture for Web Service Composition environments which enables the usage of advanced predictive and proactive time management features.