Niels Lohmann’s research while affiliated with University of Rostock and other places

Business process modeling is still a challenging task — especially since more and more aspects are added to the models, such as data lifecycles, security constraints, or compliance rules. At the same time, formal methods allow for a detection of errors in the early modeling phase. Detected errors are usually explained with a path from the initial to the error state. These paths can grow unmanageably and make the understanding and fixing of errors very time consuming. This paper addresses this issue and proposes a novel explanation of errors: Instead of listing the actions on the path to the error, only the decisions that lead to it are reported and highlighted in the original model. Furthermore, we exploit concurrency to create a compact artifact to explain errors.

Despite the correct deployment of access control mechanisms, information leaks can persist and threaten the reliability of business process execution. This paper presents an automated and effective approach for the verification of information flow control for business process models. Building on the concept of place-based non-interference and declassification, the core contribution of this paper is the application of Petri net reachability to detect places in which information leaks occur. Such a feature allows for the use of state-of-the-art tool support to model-check business process models and detect leaks. We show that the approach is sound and complete, and present the Anica tool to identify leaks. An extensive evaluation comprising over 550 industrial process models is carried out and shows that information flow analysis of process models can be done in milliseconds. This motivates a tight integration of business process modeling and non-interference checking.

We consider services as units in interorganizational business processes. Following trends in the business process management community, we switch from an activity-centric description of processes to artifact-centric descriptions. In the interorganizational setting, unique problems arise. For instance, an artifact hub that is crucial for present-day enactment of artifact-centric processes, can hardly be shared between different organizations since the stored information may be subject to trade secrets. We propose a solution that involves the translation of an artifact-centric model into an activity-centric model. In this course, we consider artifacts as entities that may be sent around between organizations. The location of an artifact may imply access restrictions for one or the other organization. We propose both a formal model and algorithms to show the effectiveness of our approach. © 2014 Springer Science+Business Media New York. All rights are reserved.

This document presents the results of the Model Checking Contest held at Petri Nets 2013 in Milano. This contest aimed at a fair and experimental evaluation of the performances of model checking techniques applied to Petri nets. This is the third edition after two successful editions in 2011 and 2012. The participating tools were compared on several examinations (state space generation and evaluation of several types of formul{\ae} -- reachability, LTL, CTL for various classes of atomic propositions) run on a set of common models (Place/Transition and Symmetric Petri nets). After a short overview of the contest, this paper provides the raw results from the contest, model per model and examination per examination. An HTML version of this report is also provided (http://mcc.lip6.fr).

One driver of business process management is the opportunity to reduce costs by outsourcing certain tasks to third-party organizations. At the same time, it is undesirable that delicate information (e.,g., trade secrets) "leak" to the involved third parties, be it for legal or economic reasons. The absence of such leaks - called noninterference - can be checked automatically. Such a check requires an assignment of each task of the business process as either confidential or public. Drawbacks of this method are that (1) this assignment of every task is cumbersome, (2) an unsuccessful check requires a corrected confidentiality assignment although (3) the diagnosis and correction of information leaks is a nontrivial task. This paper presents a modeling prototype that integrates the noninterference check into the early design phase of an interorganizational business process. It not only allows for instant feedback on confidentiality assignments, but also for an automated completion of partial assignments toward guaranteed noninterference.

This book constitutes the thoroughly refereed post-workshop proceedings of the 9th International Workshop on Web Services and Formal Methods, WS-FM 2012, held in Tallinn, Estonia, in September 2012. The 9 papers presented were carefully reviewed and selected from 19 submissions. They cover aspects such as the modeling and analysis of web services, service discovery, and service coordination with formal methods like BPEL, CSP, Maude, and Petri nets.

This article presents the results of the Model Checking Contest held at Petri Nets 2012 in Hambourg. This contest aimed at a fair and experimental evaluation of the performances of model checking techniques applied to Petri nets. This is the second edition after a successful one in 2011. The participating tools were compared on several examinations (state space generation and evaluation of several types of formulae - structural, reachability, LTL, CTL) run on a set of common models (Place/Transition and Symmetric Petri nets). After a short overview of the contest, this paper provides the raw results from the context, model per model and examination per examination.