[drools-user] Logical Assertions

[Russ Egan]

Can someone explain or point me to an explanation of a "logical assertion"? 
And related "truth maintainance"?  I see the integration test, using "assertLogical" 
but I don't understand what it does.

does this mean that if a fact is asserted in the RHS of a rule, that when 
the LHS of the rule becomes false, the fact is automatically retracted?

thanks