Tijs Slaats

Nested dynamic condition response graphs

We present an extension of the recently introduced declarative process model Dynamic Condition Response Graphs (DCR Graphs) to allow nested sub-graphs and a new milestone relation between events. The extension was developed during a case study carried out jointly with our industrial partner Exformatics, a danish provider of case and workflow management systems. We formalize the semantics by giving first a map from Nested to (flat) DCR Graphs with milestones, and then extending the previously given mapping from DCR Graphs to Buchi-automata to include the milestone relation.

Declarative modeling: an academic dream or the future for BPM?

Declarative modeling has attracted much attention over the last years, resulting in the development of several academic declarative modeling techniques and tools. The absence of empirical evaluations on their use and usefulness, however, raises the question whether practitioners are attracted to using those techniques. In this paper, we present a study on what practitioners think of declarative modeling. We show that the practitioners we involved in this study are receptive to the idea of a hybrid approach combining imperative and declarative techniques, rather than making a full shift from the imperative to the declarative paradigm. Moreover, we report on requirements, use cases, limitations, and tool support of such a hybrid approach. Based on the gained insight, we propose a research agenda for the development of this novel modeling approach.

Mixing paradigms for more comprehensible models

Petri nets efficiently model both data- and control-flow. Control-flow is either modeled explicitly as flow of a specific kind of data, or implicit based on the data-flow. Explicit modeling of control-flow is useful for well-known and highly structured processes, but may make modeling of abstract features of models, or processes which are highly dynamic, overly complex. Declarative modeling, such as is supported by Declare and DCR graphs, focus on control-flow, but does not specify it explicitly; instead specifications come in the form of constraints on the order or appearance of tasks. In this paper we propose a combination of the two, using colored Petri nets instead of plain Petri nets to provide full data support. The combined approach makes it possible to add a focus on data to declarative languages, and to remove focus from the explicit control-flow from Petri nets for dynamic or abstract processes. In addition to enriching both procedural processes in the form of Petri nets and declarative processes, we also support a flow from modeling only abstract data- and control-flow of a model towards a more explicit control-flow model if so desired. We define our combined approach, and provide considerations necessary for enactment. Our approach has been implemented in CPN Tools 4.

The Automated Discovery of Hybrid Processes

The declarative-procedural dichotomy is highly relevant when choosing the most suitable process modeling language to represent a discovered process. Less-structured processes with a high level of variability can be described in a more compact way using a declarative language. By contrast, procedural process modeling languages seem more suitable to describe structured and stable processes. However, in various cases, a process may incorporate parts that are better captured in a declarative fashion, while other parts are more suitable to be described procedurally. In this paper, we present a technique for discovering from an event log a so-called hybrid process model. A hybrid process model is hierarchical, where each of its sub-processes may be specified in a declarative or procedural fashion. We have implemented the proposed approach as a plug-in of the ProM platform. To evaluate the approach, we used our plug-in to mine a real-life log from a financial context.

Contracts for Cross-organizational Workflows as Timed Dynamic Condition Response Graphs

We conservatively extend the declarative Dynamic Condition Response (DCR) Graph process model, introduced in the PhD thesis of the second author, to allow for discrete time deadlines. We prove that safety and liveness properties can be verified by mapping finite timed DCR Graphs to finite state transition systems. We exemplify how deadlines can introduce time-locks and deadlocks and violate liveness. We then prove that the general technique for safe distribution of DCR Graphs provided in previous work can be extended to timed DCR Graphs. We exemplify the use of timed DCR Graphs and the distribution technique in praxis on a timed extension of a cross-organizational case management process arising from a previous case study. The example shows how a timed DCR Graph can be used to describe the global contract for a timed workflow process involving several organizations, which can then be distributed as a network of communicating timed DCR Graphs describing the local contract for each organization.

Blockchains for Business Process Management - Challenges and Opportunities

Blockchain technology offers a sizable promise to rethink the way interorganizational business processes are managed because of its potential to realize execution without a central party serving as a single point of trust (and failure). To stimulate research on this promise and the limits thereof, in this article, we outline the challenges and opportunities of blockchain for business process management (BPM). We first reflect how blockchains could be used in the context of the established BPM lifecycle and second how they might become relevant beyond. We conclude our discourse with a summary of seven research directions for investigating the application of blockchain technology in the context of BPM.

Safe distribution of declarative processes

We give a general technique for safe distribution of a declarative (global) process as a network of (local) synchronously communicating declarative processes. Both the global and local processes are given as Dynamic Condition Response (DCR) Graphs. DCR Graphs is a recently introduced declarative process model generalizing labelled prime event structures to a systems model able to finitely represent ω-regular languages. An operational semantics given as a transition semantics between markings of the graph allows DCR Graphs to be conveniently used as both specification and execution model. The technique for distribution is based on a new general notion of projection of DCR Graphs relative to a subset of labels and events identifying the set of external events that must be communicated from the other processes in the network in order for the distribution to be safe. We prove that for any vector of projections that covers a DCR Graph that the network of synchronously communicating DCR Graphs given by the projections is bisimilar to the original global process graph. We exemplify the distribution technique on a process identified in a case study of an cross-organizational case management system carried out jointly with Exformatics A/S.

A Case for Declarative Process Modelling: Agile Development of a Grant Application System

We report on a recent industrial project carried out by Exformatics A/S in which the company used the declarative DCR Graphs notation to model and implement the grant application process of a Danish foundation. We present the process and discuss the advantages of the approach and challenges faced both while modelling and implementing the process. Finally, we discuss current work on extensions to the DCR Graphs notation aiming to address the challenges raised by the case study and to support the declarative, agile approach.

Towards Trustworthy Adaptive Case Management with Dynamic Condition Response Graphs

We describe how the declarative Dynamic Condition Response (DCR) Graphs process model can be used for trustworthy adaptive case management by leveraging the flexible execution, dynamic composition and adaptation supported by DCR Graphs. The dynamically composed and adapted graphs are verified for deadlock freedom and liveness in the SPIN model checker by utilizing a mapping from DCR Graphs to PROMELA code. We exemplify the approach by a small workflow extracted from a field study at a danish hospital.

Designing a Cross-Organizational Case Management System Using Dynamic Condition Response Graphs

We present a case study of the use of Dynamic Condition Response (DCR) Graphs, a recently introduced declarative business process model, in the design of a cross-organizational case management system being developed by Exformatics A/S, a Danish provider of knowledge and workflow management systems. We show how DCR Graphs allow to capture directly both the behavioral constraints identified during meetings with the customer and the operational execution as markings of the graph. In comparison, imperative models such as BPMN, Petri Net, UML Sequence or Activity diagrams are only good at describing the operational way to fulfill the constraints, leaving the constraints implicit. In particular, we point out that the BPMN ad-hoc sub process activity, intended to support more loosely structured goal driven ad-hoc processes, is inconsistently described in the final version of the BPMN 2.0 standard. The case study motivated an extension of the DCR Graphs model to nested graphs and the development of graphical design and simulation tools to increase the understanding of the models. The study also revealed a number of challenges for future research in techniques for model-driven design of cross-organizational process-aware information systems combining declarative and imperative models.