[rules-users] ClassCastException and other problems

Hi there, I have three issues, where I'm not sure if these are bugs in drools, or if this is just the way it has to be. the used classes in this case are: Project Model ProcessModel extends Model only the Project is in the working memory, because I didn't want to load all elements due to performance issues (there can be thousends of elements to load at startup). if I have the following rule: Project($models : models) ProcessModel($activities : activities) from $models there happen to be two problems. if the project does not only contain ProcessModels but also TypeModels or others (all extend Model), this leads to a ClassCastException. I can solve this by writing the rule as follows: Project($models : models) $m : Model(eval($m instanceof ProcessModel)) from $models ProcessModel($activities : activities) from $m but this is not really nice and I hope there is a better solution for this, is there? the second problem this rule gives me, is when the set 'models' is empty. that will also throw an exception. to solve this I write: $p : Project(eval($p.hasModels()), $models : models) $m : Model(eval($m instanceof ProcessModel)) from $models ProcessModel($activities : activities) from $m and I need to use this in each case where I have possible empty sets. the last problem I encountered when I tried to load all elements to the working memory and then redefine some rules. used classes: Aggregation extends DomainElement rule: Aggregation(owner.owner != type.owner) causes some exception. the root exception is a ClassCastException: ProxyShadowProxy cannot be cast to Aggregation. when I rewrite the rule as: $element : DomainElement(eval($element instanceof Aggregation)) Aggregation(owner.owner != type.owner) from $element everything works fine. but that again is not a nice solution. any help? best regards sibylle