Pattern 7 (Alternative Representation)
FLASH animation of Alternative Representation pattern
Description
This pattern denotes the ability to capture process modeling concepts without the use of their primary graphical notation.
Purpose
To avoid cluttering and potentially reduce model size, especially in large or complex models.
Rationale
Specific classes of users may be more familiar with certain symbols [6]. Reducing model size positively affects model understanding [37].
Realization
A typical case of alternative representation is that of the OR-split gateway, which replaces a combination of XOR and AND split gateways. This is supported by eEPCs,BPMN and YAWL. BPMN also offers a number of alternative (shorthand) representations. For example, an AND-split can be replaced by specifying multiple outgoing edges from an activity; an (X)OR split can be replaced by Conditional Flows; an XOR-join can be subsumed by multiple incoming edges to an activity; an incoming/outgoing message flow can be directly connected to an activity (thus avoiding the use of a message event or a receive/send activity); a structured loop can be replaced by an activity annotated with a Loop marker. UML ADs offer similar alternative notations for the AND-split and the (X)OR split, while the AND-join is subsumed by multiple incoming edges to an activity. Semantically, conditions and tasks need to alternate in YAWL. However conditions can be omitted from the graphical representation of a model when connected only to one preceding and to one subsequent task. These alternative representations are generally supported by the main modeling editors, see e.g. Enterprise Architect for UML ADs, ARIS and Oryx for BPMN, and the YAWL Editor for YAWL. Moreover, Enterprise Architect allow one to replace the predefined shape of a modeling element with an image whereas ARIS provides a Symbol Editor to create alternative representations for each modeling element. These symbols can be organized in templates for specific needs (e.g. a template for presentation to a business audience) and be applied systematically to a process model. In the literature, this feature was already envisaged by Becker et al. [9] under the name of Representation Variation, through which the classical EPC symbols can be replaced with custom-made ones, as part of adapting a process model to the requirements of an organization. An occurrence of this pattern is in , [18], where the authors define an alternative representation for those edges with numerous bends or that cross other edges: they cut the edge and insert two pointers at the two ends. In this way, clutter can be reduced.
Example
Figure 7 shows the model in Figure 3b after applying the BPMN alternative representation for XOR-split, XOR-join and AND-split.
