[rules-users] help! asserting facts before reading rules?

I have a dummy program that asserts 2 simple facts into working memory, then reads a simple rule file into the rule base, then fires the rules. I've attached the rules and the NullPointerException that results. However, if I read the rules first then assert the facts, the program runs fine. Alternatively, if I modify the second rule such that the modify occurs before the retract, the program runs fine even if I assert the facts first then read the rules. In general, I may not be able to control when facts are asserted vs. when rules are read in. Should this be a problem? Any hints greatly appreciated!! Thanks, Justine simple.drl: rule "setupFactC" no-loop true when a: factA(s:field1, i:field2, f:field3) not c : factC(f1==s) then assert(s != null ? new factC(s, i, f) : new factC()); end rule "factBWithRetract" no-loop true when b : factB(s:f1, i:f2, f:f3) a : factA(field1==s) c : factC(f1==s) then c.setF3(f); retract(b); modify(c); end Stack trace: java.lang.NullPointerException at org.drools.base.com.vsasset.rules.isolate.factB$getF1.getValue(Unknown Source) at org.drools.base.ClassFieldExtractor.getValue(Unknown Source) at org.drools.rule.Declaration.getValue(Unknown Source) at org.drools.rule.BoundVariableConstraint.isAllowed(Unknown Source) at org.drools.common.BetaNodeBinder.isAllowed(Unknown Source) at org.drools.reteoo.JoinNode.modifyObject(Unknown Source) at org.drools.reteoo.ObjectSource.propagateModifyObject(Unknown Source) at org.drools.reteoo.ObjectTypeNode.modifyObject(Unknown Source) at org.drools.reteoo.Rete.modifyObject(Unknown Source) at org.drools.reteoo.ReteooRuleBase.modifyObject(Unknown Source) at org.drools.reteoo.ReteooWorkingMemory.modifyObject(Unknown Source) at org.drools.base.DefaultKnowledgeHelper.modifyObject(Unknown Source) at com.vsasset.rules.isolate.Rule_factBWithRetract_0.consequence (Rule_factBWithRetract_0.java:10) at com.vsasset.rules.isolate.Rule_factBWithRetract_0ConsequenceInvoker.evaluate (Rule_factBWithRetract_0ConsequenceInvoker.java:26) at org.drools.common.DefaultAgenda.fireActivation(Unknown Source) at org.drools.common.DefaultAgenda.fireNextItem(Unknown Source) at org.drools.common.AbstractWorkingMemory.fireAllRules(Unknown Source) at org.drools.common.AbstractWorkingMemory.fireAllRules(Unknown Source) at org.drools.common.AbstractRuleBase.addPackage(Unknown Source) at com.vsasset.rules.isolate.TestCase.main(TestCase.java:36) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke( NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke( DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:585) at com.intellij.rt.execution.application.AppMain.main(AppMain.java:90) Exception in thread "main" org.drools.spi.ConsequenceException: java.lang.NullPointerException at org.drools.common.DefaultAgenda.fireActivation(Unknown Source) at org.drools.common.DefaultAgenda.fireNextItem(Unknown Source) at org.drools.common.AbstractWorkingMemory.fireAllRules(Unknown Source) at org.drools.common.AbstractWorkingMemory.fireAllRules(Unknown Source) at org.drools.common.AbstractRuleBase.addPackage(Unknown Source) at com.vsasset.rules.isolate.TestCase.main(TestCase.java:36) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke( NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke( DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:585) at com.intellij.rt.execution.application.AppMain.main(AppMain.java:90)