Nowadays, BPMN is a de-facto standard for modeling multiple participants processes as collaboration diagrams. BPMN collaboration can be heavily influenced by the physical environment in which the involved participants act. Indeed, they can occupy a position, move in the space, make decisions according to the environment's status, and change it. However, BPMN lacks support for integrating the environment. To overcome this limitation, we present BEAR, a tool for modeling and animating together a BPMN collaboration and its environment in the form of a place graph. BEAR supports designers in precisely understanding the interplay between BPMN collaborations and the environment.
Business Process Model and Notation (BPMN) [
The collaboration execution often depends on its working physical environment, in particular
on the topology of the space and the environmental attributes, e.g., temperature, lighting, weather
conditions, and network connectivity. Thus, in modeling such collaborations, it is crucial to consider
the environment where participants operate [
In this regard, the literature increasingly deals with the environment concept within BPMN [
To enforce these findings and better guarantee a more precise understanding of the interplay between BPMN collaboration and the environment, we propose BEAR (BPMN Environmental Animator). BEAR is a novel BPMN animator tool that provides the user with a modeling environment to model environmental BPMN collaborations and observe their execution through the flow of tokens over the diagram and the evolution of environmental attributes.
It is indeed well known from the literature that animator tools play an important role in easing the
understanding of the behavior of business processes [
CEUR
ceur-ws.org
animate BPMN models. For instance, Allweyer and Schweitzer [
The rest of the paper is organized as follows. Section 2 describes the functionalities of the BEAR tool. Section 3 assesses its maturity via case studies. Section 4 concludes the paper by providing links and information about downloading, installing, and using BEAR.
This section presents the BEAR tool and its features for supporting the understanding of the interplay between collaboration business processes and the environment. BEAR provides modeling and animation functionalities. The former allows the designer to create environmental BPMN collaboration diagrams, while the latter is used to visualize the collaboration execution and the evolution of the environment. The BEAR Modeler The interface of the BEAR modeler (Figure 1) is divided into two main parts i.e., the BPMN modeler on the left and the environment modeler on the right. The designer can use the BPMN modeler to create a collaboration diagram using the standard elements and can exploit the environment modeler to design a place graph representing the environment. A place graph consists of nodes that symbolize a predefined area and edges that define the connection between them.
In addition, using the button in the upper part of the interface, the designer can open the property panel that appears in between the two modelers. By clicking an element from one of the modelers, the property panel permits to add information related to the selected element and use them to drive the animation. Starting from the place graph, the designer can insert a list of attributes characterizing the environment in each place. These attributes are key-value pairs, e.g., alarm = false accessible by each process in the collaboration by using the place name in front of the attribute name, e.g., place1.alarm. All place attributes are accessible by the element of the BPMN collaboration in order to react and change them. Similarly, the property panel shows for each BPMN element, beyond the already existing properties like element name and identifier, it is possible to set new additional information related to the interplay with the environment and to process data. In particular, selecting a pool element, we added a new property called position that states the initial place of the participant represented by the pool. This property appears in BEAR as a select box that lists all the place names in the place graph. While selecting a data object, the designer can define process variables and instantiate them with a value e.g., target = place1. Such data are accessible only by process elements of the same pool like tasks, events, and gateways, making it possible to store, manipulate, and share information also related to the environment. About tasks, the designer can specify (i) a guard condition, used to constrain the execution of the task to specific values of data object and environmental attributes; (iii) a list of assignments, used to modify the environment topology (by adding and/or deleting nodes and/or places) or the values of data object and environmental attributes; and (iii) a destination, used to define a place in the place graph to reach from the current participant position. The destination can be static e.g., place1 or dynamic using a data object attribute valorized at run-time with a place name. If the destination is null, the task does not involve any movement. For what concerns events the designer can define message events (start, intermediate, end) with value passing. Specifically, send events can exhibit a payload in the form of values e.g., "Payload" or 3; or attribute names e.g., place1.attr. While receive events can exhibit an attribute name where to store the received payload. We also adopt, conditional events (start and boundary) to which the designer can add a boolean condition used to activate the event. A special condition for the conditional boundary event is the unreachability, used to react in case the participant can not reach its destination. Finally, boolean expressions can be assigned to the outgoing sequence flows of XOR gateways to drive decisions dynamically.
The BEAR Animator The key characteristic of the BEAR Animator (Figure 2) is its dynamic visual
animation. It shows, in a step-by-step fashion, the evolution of the BPMN collaboration with its
environment. By selecting the Token Simulation in the BEAR interface, a play button will appear over
each fireable start event. Once this button is clicked, one process is activated. This creates a new token
in the form of a small colored circle at the start event of the BPMN process and another token in the
place of the place graph model corresponding to the value of the position property set on the pool.
Then, the token starts to cross the BPMN collaboration model and the environment model according to
the operational rules induced by our formal semantics [
The animation terminates once all tokens cannot move forward. In case a token remains blocked due to data object or environmental attributes valorization, e.g. a guard condition violation, BEAR highlights it in red (Figure 2). Indeed, at any time, the animation can be paused by the user to check the distribution of tokens in the environment and into the BPMN collaboration. From a practical point of view, this allows designers to debug their environmental BPMN collaboration models. They can detect undesired executions, where e.g. a control flow is blocked, and deduce the cause beyond it by possibly checking the tokens marking the BPMN model and the place graph.
The BEAR tool is a web application written in JavaScript. It extends the bpmn-js1 toolkit and its token
simulation plug-in [
To assess the maturity of BEAR, we designed and implemented eleven case studies belonging to
diferent application domains (e.g. agriculture, transport, restaurant, library, sale of products, and
logistics), three of which are inspired by the literature [
The evaluation of these case studies has shown how environmental conditions can change the outcome of the collaboration process. For the sake of presentation, we briefly discuss one of the case studies concerning a fire-extinguishing collaboration in a student dormitory. The collaboration is performed by a fire control system and a fire-fighting autonomous robot. The fire control system is in charge of detecting fire in dormitory rooms through fire sensors and informing the extinguisher robot that will reach the fire to extinguish it. The dormitory, inhabited by students, comprises a kitchen, an entrance, three bedrooms, two bathrooms, and a living room connected by a corridor. Each room has a door and a fire sensor. The collaboration starts when the fire control system detects the presence of fire in one of the dormitory rooms. In this case, the fire control system notifies the fire-fighting robot of the position of the fire and then activates the alarm. As soon as the robot receives the notification, it moves toward the fire and, after extinguishing it, sends feedback to the control system, which turns of the alarm. Notably, apart from the fire control system and the fire-fighting robot, some students in the dormitory perform their daily routines interacting with the environment. Based on this scenario, the BEAR animation can show two slightly diferent outcomes. Indeed, if the doors in the dormitory are open, the fire-fighter can reach any place if the fire occurs. In the case the student closes a door, she/he can make a room unreachable by the fire-fighter , which may be unable to extinguish the fire (Figure 3). The environmental BPMN collaboration models exemplifying these two outcomes are made available in the repository referenced in the next section.
We provide the BEAR tool under the MIT license and in diferent forms, i.e., source code, online service, and a Docker image. Moreover, we provide a detailed user guide explaining how to install and use the tool, the environmental BPMN collaboration models and the description of each case study. Finally, we provide a screencast showing the modeling and animation of the fire-extinguishing collaboration described in Section 3. All the mentioned resources are available at https://pros.unicam.it/ environmental-bpmn/.