Kristian Bisgaard Lassen

Translating unstructured workflow processes to readable BPEL: Theory and implementation

The Business Process Execution Language for Web Services (BPEL) has emerged as the de facto standard for implementing processes. Although intended as a language for connecting web services, its application is not limited to cross-organizational processes. It is expected that in the near future a wide variety of process-aware information systems will be realized using BPEL. While being a powerful language, BPEL is difficult to use. Its XML representation is very verbose and only readable for the trained eye. It offers many constructs and typically things can be implemented in many ways, e.g., using links and the flow construct or using sequences and switches. As a result only experienced users are able to select the right construct. Several vendors offer a graphical interface that generates BPEL code. However, the graphical representations are a direct reflection of the BPEL code and not easy to use by end-users. Therefore, we provide a mapping from Workflow Nets (WF-nets) to BPEL. This mapping builds on the rich theory of Petri nets and can also be used to map other languages (e.g., UML, EPC, BPMN, etc.) onto BPEL. In addition to this we have implemented the algorithm in a tool called WorkflowNet2BPEL4WS.

Complexity metrics for Workflow nets

Process modeling languages such as EPCs, BPMN, flow charts, UML activity diagrams, Petri nets, etc., are used to model business processes and to configure process-aware information systems. It is known that users have problems understanding these diagrams. In fact, even process engineers and system analysts have difficulties in grasping the dynamics implied by a process model. Recent empirical studies show that people make numerous errors when modeling complex business processes, e.g., about 20% of the EPCs in the SAP reference model have design flaws resulting in potential deadlocks, livelocks, etc. It seems obvious that the complexity of the model contributes to design errors and a lack of understanding. It is not easy to measure complexity, however. This paper presents three complexity metrics that have been implemented in the process analysis tool ProM. The metrics are defined for a subclass of Petri nets named Workflow nets, but the results can easily be applied to other languages. To demonstrate the applicability of these metrics, we have applied our approach and tool to 262 relatively complex Protos models made in the context of various student projects. This allows us to validate and compare the different metrics. It turns out that our new metric focusing on the structuredness outperforms existing metrics.

Let’s go all the way: from requirements via colored workflow nets to a BPEL implementation of a new bank system

This paper describes use of the formal modeling language Colored Petri Nets (CPNs) in the development of a new bank system. As a basis for the paper, we present a requirements model, in the form of a CPN, which describes a new bank work process that must be supported by the new system. This model has been used to specify, validate, and elicit user requirements. The contribution of this paper is to describe two translation steps that go from the requirements CPN to an implementation of the new system. In the first translation step, a workflow model is derived from the requirements model. This model is represented in terms of a so-called Colored Workflow Net (CWN), which is a generalization of the classical workflow nets to CPN. In the second translation step, the CWN is translated into implementation code. The target implementation language is BPEL4WS deployed in the context of IBM WebSphere. A semi-automatic translation of the workflow model to BPEL4WS is possible because of the structural requirements imposed on CWNs.

On the transformation of control flow between block-oriented and graph-oriented process modelling languages

Much recent research work discusses the transformation between different process modelling languages. This work, however, is mainly focussed on specific process modelling languages, and thus the general reusability of the applied transformation concepts is rather limited. In this paper, we aim to abstract from concrete transformations by distinguishing two major paradigms for representing control flow in process modelling languages: block-oriented languages (such as BPEL and BPML) and graph-oriented languages (such as BPMN, EPCs, and YAWL). The contribution of this paper are generic strategies for transforming from block-oriented process languages to graph-oriented languages, and vice versa.

WorkflowNet2BPEL4WS: a tool for translating unstructured workflow processes to readable BPEL

This paper presents WorkflowNet2BPEL4WS a tool to automatically map a graphical workflow model expressed in terms of Workflow Nets (WF-nets) onto BPEL The Business Process Execution Language for Web Services (BPEL) has emerged as the de-facto standard for implementing processes and is supported by an increasing number of systems (cf the IBM WebSphere Choreographer and the Oracle BPEL Process Manager) While being a powerful language, BPEL is difficult to use Its XML representation is very verbose and only readable for the trained eye It offers many constructs and typically things can be implemented in many ways, e.g., using links and the flow construct or using sequences and switches As a result only experienced users are able to select the right construct Some vendors offer a graphical interface that generates BPEL code However, the graphical representations are a direct reflection of the BPEL code and not easy to use by end-users Therefore, we provide a mapping from WF-nets to BPEL This mapping builds on the rich theory of Petri nets and can also be used to map other languages (e.g., UML, EPC, BPMN, etc.) onto BPEL To evaluate WorkflowNet2BPEL4WS we used more than 100 processes modeled using Protos (the most widely used business process modeling tool in the Netherlands), automatically converted these into CPN Tools, and applied our mapping The results of these evaluation are very encouraging and show the applicability of our approach.

The BRITNeY suite animation tool

This paper describes the BRITNeY suite, a tool which enables users to create visualizations of formal models. BRITNeY suite is integrated with CPN Tools, and we give an example of how to extend a simple stop-and-wait protocol with a visualization in the form of message sequence charts. We also show examples of animations created during industrial projects to give an impression of what is possible with the BRITNeY suite.

From task descriptions via colored Petri nets towards an implementation of a new electronic patient record workflow system

We consider a given specification of functional requirements for a new electronic patient record system for Fyn County, Denmark. The requirements are expressed as task descriptions, which are informal descriptions of work processes to be supported. We describe how these task descriptions are used as a basis to construct two executable models in the formal modeling language Colored Petri Nets (CPNs). The first CPN model is used as an execution engine for a graphical animation, which constitutes a so-called Executable Use Case (EUC). The EUC is a prototype-like representation of the task descriptions that can help to validate and elicit requirements. The second CPN model is a Colored Workflow Net (CWN). The CWN is derived from the EUC. Together, the EUC and the CWN are used to close the gap between the given requirements specification and the realization of these requirements with the help of an IT system. We demonstrate how the CWN can be translated into the YAWL workflow language, thus resulting in an operational IT system.

Requirements Validation: Execution of UML Models with CPN Tools

Requirements validation is a critical task in any engineering project. The confrontation of stakeholders with static requirements models is not enough, since stakeholders with non-computer science education are not able to discover all the inter-dependencies between the elicited requirements. Even with simple unified modelling language (UML) requirements models, it is not easy for the development team to get confidence on the stakeholders’ requirements validation. This paper describes an approach, based on the construction of executable interactive prototypes, to support the validation of workflow requirements, where the system to be built must explicitly support the interaction between people within a pervasive cooperative workflow execution. A case study from a real project is used to illustrate the proposed approach.

From Requirements via Colored Workflow Nets to an Implementation in Several Workflow Systems

Hospitals and other healthcare organizations need to support complex and dynamic workflows. Moreover, these processes typically invoke a number of medical disciplines. This makes it important to avoid the typical disconnect between requirements and the actual implementation of the system. In this paper we apply a development approach where an Executable Use Case (EUC) and a Colored Workflow Net (CWN) are used to close the gap between a given requirements specification and the realization of these requirements based on workflow technology. In order to do so, we describe a large case study where the diagnostic process of the gynecological oncology care process of the Academic Medical Center (AMC) hospital is used as a candidate process. The process consists of hundreds of activities. These have been modeled and analyzed using an EUC and a CWN. Moreover, based on the CWN, the process has been implemented using four different workflow systems. In this way, we demonstrate the general application of the approach and its applicability to distinct technology systems.

Translating Message Sequence Charts to other Process Languages Using Process Mining

Message Sequence Charts (MSCs) are often used by software analysts when discussing the behavior of a system with different stakeholders. Often such discussions lead to more complete behavioral models in the form of, e.g., Event-driven Process Chains (EPCs), Unified Modeling Language (UML), activity diagrams, Business Process Modeling Notation (BPMN) models, Petri nets, etc. Process mining on the other hand, deals with the problem of constructing complete behavioral models by analyzing event logs of information systems. In contrast to existing process mining techniques, where logs are assumed to only contain implicit information, the approach presented in this paper combines the explicit knowledge captured in individual MSCs and the techniques and tools available in the process mining domain. This combination allows us to discover high-quality process models. To constructively add to the existing work on process mining, our approach has been implemented in the process mining framework ProM (www.processmining.org).