The temporal perspective in business process modeling: a survey and research challenges

Dynamic Controllability of Processes without Surprises

Dynamic controllability guarantees that a process control can steer the execution of a business process without violating any temporal constraints although some tasks have uncontrollable durations. However, it has been shown that dynamic controllability may lead to process executions with the undesirable property that tasks have to be started or ended on extremely short notice. Sudden termination forces the agent to immediately terminate the execution of a process task without any prior notice in order to meet some temporal constraints. Semi-dynamic controllability guarantees dynamic controllability and the absence of sudden termination. Here, we show that dynamic controllability may also lead to the problem of sudden start, which forces the immediate start of a process task without prior notice. We formalize all constellations of temporal constraints causing sudden start and sudden termination in a process. We propose a technique to design processes in which activities can be dynamically dispatched without these surprises, i.e., with advance notice, and extend the notion of semi-dynamic controllability by also considering the sudden start. This leads to a sound and complete algorithm for checking the semi-dynamic controllability of time-constrained processes.

Which Event Happened First? Deferred Choice on Blockchain Using Oracles

First come, first served: Critical choices between alternative actions are often made based on events external to an organization, and reacting promptly to their occurrence can be a major advantage over the competition. In Business Process Management (BPM), such deferred choices can be expressed in process models, and they are an important aspect of process engines. Blockchain-based process execution approaches are no exception to this, but are severely limited by the inherent properties of the platform: The isolated environment prevents direct access to external entities and data, and the non-continual runtime based entirely on atomic transactions impedes the monitoring and detection of events. In this paper we provide an in-depth examination of the semantics of deferred choice, and transfer them to environments such as the blockchain. We introduce and compare several oracle architectures able to satisfy certain requirements, and show that they can be implemented using state-of-the-art blockchain technology.

Scheduling Processes Without Sudden Termination

Dynamic controllability is the most general criterion to guarantee that a process can be executed without time failures. However, it admits schedules with an undesirable property: starting an activity without knowing its deadline. We analyze the specific constellations of temporal constraints causing such a sudden termination. Consequently, we introduce the somewhat stricter notion of semi-dynamic controllability, and present necessary and sufficient conditions to guarantee that a process can be executed without time failures and without sudden termination. A sound and complete algorithm for checking whether a process is semi-dynamically controllable complements the approach.