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The YAWL (Yet Another Workflow Language) workflow language supports the most frequent control-flow patterns found in the current workflow practice. As a result, most workflow languages can be mapped onto YAWL without loss of control-flow details, even languages allowing for advanced constructs such as cancellation regions and OR-joins. At the moment no analysis techniques are available for such languages, because both cancellation regions and OR-joins are non-local properties and therefore difficult to verify. Hence, a verification approach for YAWL is desirable, because such an approach could be used for any workflow language that can be mapped onto YAWL. The WofYAWL tool introduces a verification approach for YAWL that abstracts from the actual semantics of the OR-join. This approach is correct (errors reported are really errors), but not necessarily complete (not every error might get reported). This incompleteness is due to the fact that the approach approximates the OR-join semantics. Nevertheless, our approach can be used to successfully detect errors in YAWL models. Moreover, the approach can easily be transferred to other workflow languages allowing for advanced constructs such as cancellations and OR-joins.

The SAP reference model contains more than 600 non-trivial process models expressed in terms of EPCs. We have analyzed these models using WofYAWL (after having converted the EPCs into YAWL models). We discovered that at least 34 of these EPCs contain errors (i.e., at least 5.6% is flawed). We analyzed which parts of the SAP reference model contain most errors. Moreover, based on 15 characteristics (e.g., the size of the model), we used logistic regression to find possible predictors for these errors. This systematic analysis of the SAP reference model illustrates the need for verification