This paper presents a web-based editor that o ers YAWL editing capabilities and comprehensive support for the XML format of YAWL. The open-source project Signavio Core Components is extended with a graphical user interface (GUI) for parts of the YAWL Language, and an import-/export component that converts between YAWL and the internal format of Signavio Core Components. This conversion, between the web-based editor and the o cial YAWL Editor, is lossless so both tools may be used together. Compared to the o cial YAWL Editor, the web-based editor is missing some features, but could still facilitate the usage of the YAWL system in use cases that are not supported by a desktop application.
extensible with new process modeling languages through plug-ins. Unfortunately,
also the SCC project was discontinued in 2011, shortly after the rst release.
Nevertheless, the source-code is still available1, and e orts are made to continue
the development as part of the Apromore2 project [7]. The Apromore project also
includes the YAWL editing capabilities that are presented in this paper. Most
of the SCC editor is implemented with JavaScript that manipulates Scalable
Vector Graphics (SVG) to show and edit process models in the browser window.
For each supported process modeling language of SCC a so called Stencil Set [
The new web-based YAWL Editor consists of SCC together with three added components: the YAWL Stencil Set, a client-side component and a server-side component. The YAWL Stencil Set includes SVG graphics of all YAWL elements (e.g. Tasks, Conditions, Edges), all their properties (e.g. description, routing conditions, task variables) and basic rules regarding their interconnection. Additional rules that cannot be expressed within the Stencil Set are added through the client-side component with JavaScript. The server-side component, which is realized with Java, is responsible to convert between the YAWL XML format and the JSON format of SCC. This conversion is lossless, therefore work ows created with the original YAWL Editor can be imported, modi ed with the web-based YAWL Editor and exported back to the original YAWL Editor.
In Section 2 the functionality of the new web-based YAWL Editor is presented, then limitations of the current implementations are discussed in Section 3, and before concluding this paper related work is described in Section 4. 2
2 Apromore is a process model repository, available at: http://apromore.qut.edu.au/ export of the work ow back to the YAWL XML format. The properties Split and Join determine whether a task has split or join routing behavior. These properties provide selectable options for all combinations of routing behavior (AND, XOR, OR) and placement of the visible counterpart on the task node (Top, Left, Right, Bottom). In contrast to the original YAWL Editor, which stores subnets of a workow embedded in the work ow speci cation, upon import of the Orderful lment process all subnets have been stored separately in the repository. All composite tasks, like the task Ordering in Figure 1, just store a reference to the target subnet, as visible in the property Unfolds to net (link). The reference is stored in form of an URI that points to the subnet in the SCC repository. When using another repository (e.g. Apromore), then this reference will be an URI that points to the process model in the external repository. This way, the same subnet can be used in multiple YAWL work ow speci cations that are stored in the web-based YAWL Editor. A subnet that is created in the web-based YAWL Editor may also be exported as the rootnet of a YAWL work ow speci cation. This allows for more exibility in the creation of work ows, for example the Payment subnet could be exported as a stand-alone work ow. Of course, during generation of the YAWL XML format all referenced subnets are embedded again in order to generate valid YAWL XML.
The features Highlight Cancellation Region and Unfold to Subnet have been implemented to show that the web-based YAWL Editor can be extended with more advanced features of the o cial YAWL Editor. Highlight Cancellation Region emphasizes the nodes and edges that are in the Cancellation Region of a selected task. YAWL speci c features, like Highlight Cancellation Region, can be activated under the YAWL symbol in the menu as indicated by the arrow shown in Figure 1. The second feature, Unfold to Subnet, supports the user with the handling of subnets. Upon selecting a Composite Task a context menu appears, as shown next to the task pay in Figure 2. The user can either open the already linked subnet, create a new subnet, link the task to an existing subnet that was created before, or unlink the currently assigned subnet. The selection of an existing subnet is supported by showing a list of all available YAWL work ows in the repository of the web-based YAWL Editor.
The source code of the web-based YAWL Editor is currently available as part of the Apromore Editor: http://code.google.com/p/apromore/. Additionally, more information about future development and a demo version is available on the website: http://www.yaug.org/WebYAWLEditor. 3
The current implementation of the web-based YAWL Editor provides fewer features than the o cial YAWL Editor. The most signi cant limitations are in the area of the resource and data perspective of YAWL. At this stage of the development, the web-based YAWL Editor does not connect to the Resource Service of YAWL to look up organizational resources (e.g. Roles, Participants, Secondary Resources), but the information about the resource perspective of an imported YAWL work ow is preserved using fragments of the original YAWL XML format. In a future version, the web-based YAWL Editor could connect to the Interface R of YAWL to look up organizational resources and manipulate the stored XML fragment according to the selection. Regarding the data perspective, there is some support through structured editors, but the web-based YAWL Editor is missing look up and validation features. Figure 3 shows the structured editor for the routing predicates. New routing predicates can be added in a structured way, but the editor in Figure 3 still provides no means of automatically picking the target task, or checking the XSD expression for validity. The editor for task variables has similar limitations.
Furthermore, there are still some minor limitations regarding the visual appearance of the YAWL work ows in the web-based Editor. SCC does not support bended edges with bezier curves or splines and it is missing support for exact positioning of labels. As a result, in the web-based YAWL Editor all labels are positioned directly under the corresponding YAWL elements and edges using bezier curves or splines are shown as straight lines. 4
There have already been a few attempts bringing support for new process
modeling languages to the Oryx Editor (predecessor of SCC) similar to this approach.
For example, support for Coloured Petri Nets and UML class diagrams3. The
web-based jBPM Designer4, which is based on the Oryx Editor, is developed
as part of the jBPM project. As it is solely dedicated to BPMN 2.0 it was not
considered as starting point for the development of the web-based YAWL Editor.
Regarding to YAWL and SCC/Oryx the implementation of an automatic export
of BPMN models to YAWL in the Oryx Editor5 using the approach described
3 http://bpt.hpi.uni-potsdam.de/Oryx/OryxScreencasts
4 http://www.jboss.org/jbpm/components/designer
5 http://bpt.hpi.uni-potsdam.de/Oryx/BpmnToYawl
in [
With the web-based YAWL Editor, it is possible to create new, and modify existing YAWL work ow speci cations using solely a web browser. The web-based YAWL Editor is fully compatible with the o cial YAWL Editor. It has been tested with the publicly available work ow speci cations, which are distributed together with YAWL. The web-based YAWL Editor can be o ered as a service without the need of a local installation, and it can be integrated in existing web applications. In comparison to the original YAWL Editor some use cases are simpli ed, like the usage of YAWL in a classroom during an exercise, and new use cases are made possible, like the interactive presentation of YAWL work ow speci cations on a web site.
The web-based YAWL Editor is, furthermore, already integrated into the
process model repository Apromore. In the future, using Apromore and the
webbased YAWL Editor features like, for example, version control [
Schmidt, Jules White, Manfred Hauswirth, Pascal Hitzler, and Mukesh K. Mohania, editors, OTM Conferences (1), volume 7044 of Lecture Notes in Computer Science, pages 20{37. Springer, 2011. 5. Marcello La Rosa, Stephan Clemens, Arthur Hofstede, and Nick Russell. Appendix A The Order Ful llment Process Model. In Arthur H M ter Hofstede, Wil M P van der Aalst, Michael Adams, and Nick Russell, editors, Modern Business Process Automation, pages 599{616. Springer Berlin Heidelberg, 2010. 6. Marcello La Rosa, Marlon Dumas, Reina Uba, and Remco M. Dijkman. Merging business process models. In Robert Meersman, Tharam S. Dillon, and Pilar Herrero, editors, OTM Conferences (1), volume 6426 of Lecture Notes in Computer Science, pages 96{113. Springer, 2010. 7. Marcello La Rosa, Hajo A. Reijers, Wil M.P. van der Aalst, Remco M. Dijkman, Jan Mendling, Marlon Dumas, and Luciano Garca-Bauelos. Apromore: An advanced process model repository. Expert Systems with Applications, 38(6):7029 { 7040, 2011.