There is a named query "ProcessInstancesWaitingForEvent" that lives in a drools persistence jar under "META-INF/orm.xml".

The problem is not even that the query is wrong ( org.hibernate.QueryException: cannot dereference scalar collection element.. ), but that majority of applications that sit on top of JPA rely on its own mappings, and hence this query either:

1. Lost, since the custom "persistence.xml" will redefine the path to other mapping files

2. Will result in "Duplicate query mapping" exception if defined in a custom mapping file ( http://opensource.atlassian.com/projects/hibernate/browse/HHH-4152 )

Would be more logical not to depend that everyone knows to look inside "drools persistence jar", and to have an extensive documentation explaining "ProcessInstancesWaitingForEvent". It maybe hardcoded through @NamedQuery or just be available as an OPTIONAL file to use by Drools clients: e.g. "<mapping-file>META-INF/persistence/mapping/drools/drools-named-queries.xml</mapping-file>" ( and again: documented.. )

/Anatoly