[rules-users] Drools Flow: Variable Persistence Strategies

I'm trying to adapt the StringVariablePersister presented in http://blog.athico.com/2009/09/drools-flow-variable-persistence.html <http://blog.athico.com/2009/09/drools-flow-variable-persistence.html>I can create process instances with variable "color": private static WorkflowProcessInstance startProcess(StatefulKnowledgeSession ksession, String color) { Map<String, Object> vars = new HashMap<String, Object>(); vars.put("color", color); WorkflowProcessInstance p1 = (WorkflowProcessInstance) ksession.startProcess("com.sample.ruleflow", vars); return p1; } I can count them: select count(*) from ProcessInstanceInfo However I'm stymied as to counting process instances with a given color, as there appears to be no join column between ProcessInstanceInfo and VariableInstanceInfo. Can such a query be written? Thanks.