Pattern 12 (Extension)

FLASH animation of Extension pattern


This pattern captures features to extend the syntax and the semantics of a process modeling language, by adding new modeling concepts to the language's meta-model, or refining the existing ones. This pattern impacts all process models described by the extended meta-model. It has the reverse effect of Restriction.


To obtain either a closer match to the concepts of a particular domain, or a straightforward transformation to executable software.


Fig. 10b shows the "Home Loan" model in Fig. 6a after extending the BPMN meta-model with two Task sub- types, namely Approval and Rejection, and with one Message Event subtype, namely Fax (each captured by a stereotype). In Fig. 10b the Approval and Rejection Task stereotypes have been applied to task Reject loan, resp., Approve Loan, while the Fax stereotype has been applied to the two message events.


Extending a language's meta-model to the specific concepts of a domain makes the process models described by this language easier to understand for the audience of that domain [85], [40].


Both UML ADs and BPMN benefit from the extension capabilities of the Meta-Object Facility (MOF) [53], which provides a standardized way for refining existing ele- ment types based on stereotyping. For instance, this mech- anism has been used in [103] to extend BPMN with the concepts of variation point and variant, and in [27] to extend UML ADs with similar concepts. Moreover, various approaches exist which extend the meta-models of process modeling languages by adding new elements, rather than using stereotypes. For instance, [120] provides an extension to the BPMN meta-model to explicitly capture access control requirements. [22] extends BPMN to model non-functional aspects while [24] provides a similar extension to BPEL. BPEL4People [10] and BPELJ [18] are two further extensions of the BPEL meta-model to represent human tasks, resp., to incorporate java snippets in BPEL. Further, [110] extends UML ADs with concepts to define role-based access control aspects. EPCs have also been extended in different works with real-time concepts, object orientation, risk, and control- flow constructs of other languages [76]. UML modeling tools such as Enterprise Architect, typically support the standard UML extension mechanism of stereotypes. ARIS provides features to perform limited customizations of an eEPC meta- model (called ARIS Method). One can rename meta-model elements and attributes, and regroup attributes. However it is not possible to add new elements or attributes.