Jens Bæk Jørgensen

Application of Coloured Petri Nets in System Development

Coloured Petri Nets (CP-nets or CPNs) and their supporting computer tools have been used in a wide range of application areas such as communication protocols, software designs, and embedded systems. The practical application of CP-nets has also covered many phases of system development ranging from requirements to design, validation, and implementation. This paper presents four case studies where CP-nets and their supporting computer tools have been used in system development projects with industrial partners. The case studies have been selected such that they illustrate different application areas of CP-nets in various phases of system development.

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.

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 engineering for a pervasive health care system

We describe requirements engineering for a new pervasive health care system for hospitals in Denmark. The chosen requirements engineering approach composes iterative prototyping and explicit environment description in terms of workflow modelling. New work processes and their proposed computer support are represented via a combination of prose, formal models, and animation. The representation enables various stakeholders to make interactive investigations of requirements for the system in the context of the envisioned work processes. We describe lessons learned from collaboration between users and system developers in engineering the requirements for the new system.

Context-descriptive prototypes and their application to medicine administration

A context-descriptive prototype is an interactive graphical animation, driven by a formal, executable engine, implemented in some programming or modelling language. The two main properties of a context-descriptive prototype are: (1) it is an integrated description that describes system, work processes, and context of use; (2) it is a formal description. Because of (1), designers, including users, are provided with a means to investigate the system in the context of the envisioned work processes. Because of (2), investigations into questions of formalisation and automation, not only of the system, but also of the work processes, can be made explicitly and become subject for discussions and further elaboration. We describe a concrete context-descriptive prototype of the hospital work process medicine administration and its support by a new pervasive system. We discuss findings from evaluation of the prototype in cooperation with nurses, and finally compare context-descriptive prototypes with other kinds of prototypes.

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.

Formal requirements modelling with executable use cases and coloured Petri nets

This paper presents executable use cases (EUCs), which constitute a model-based approach to requirements engineering. EUCs may be used as a supplement to model-driven development (MDD) and can describe and link user-level requirements and more technical software specifications. In MDD, user-level requirements are not always explicitly described, since usually it is sufficient that one provides a specification, or platform-independent model, of the software that is to be developed. Therefore, a combination of EUCs and MDD may have potential to cover the path from user-level requirements via specifications to implementations of computer-based systems.

Executable Design Models for a Pervasive Healthcare Middleware System

UML is applied in the design of a pervasive healthcare middleware system for the hospitals in Aarhus County, Denmark. It works well for the modelling of static aspects of the system, but with respect to describing the behaviour, UML is not sufficient. This paper explains why and, as a remedy, suggests to supplement the UML models with behaviour descriptions in the modelling language Coloured Petri Nets, CPN. CPN models are executable and fine-grained, and a combined use of UML and CPN thus supports design-time investigation of the detailed behaviour of system components. In this way, the behavioural consequences of alternative design proposals may be evaluated and compared, based on models and prior to implementation.

Modelling and Analysis of Distributed Program Execution in BETA Using Coloured Petri Nets

Recently, abstractions supporting distributed program execution in the object-oriented language BETA have been designed. A BETA object on one computer may invoke a remote object, i.e., an object hosted by another computer. In this project, the formalism of Coloured Petri Nets (CP-nets or CPN) is used to describe and analyse the protocol for remote object invocation. In the first place, we build a model in order to describe, understand, and improve the protocol. Remote object invocation in BETA is modelled on the level of threads (lightweight processes) with emphasis on the competition for access to critical regions and shared resources. Secondly, the model is analysed. It is formally proved that it has a set of desirable properties, e.g., absence of dead markings.

Addressing problem frame concerns via coloured petri nets and graphical animation

To address a frame concern in Jacksons Problem Frames, we must make appropriate descriptions of: (1) the problem domain; (2) the requirements; (3) the specification of the machine. Based on these descriptions, we must give a convincing argument that the given domain properties and the machine specification together entail that the requirements are fulfilled. In this paper, we demonstrate how to address certain frame concerns with the use of the formal modelling language Coloured Petri Nets (CPN). Problem domain description and machine specification are brought together in a CPN model, which is augmented with a graphical animation. The CPN model is executable and we simulate it to address frame concerns. We illustrate the approach on the elevator controller example.