Business rule execute only once on jbpm process - drools

Question

I execute a business rule from a process on Jbpm, the rule is simple:
package com.test.flow;
rule "sample"
ruleflow-group "test"
when
then
System.out.println("Hello World");
end
But, I don't no why, this rule execute only once, for instance, I run a new instance of the process and in the jbpm console print "Hello World", but, when I run a second instance of the process doesn print anymore "Hello World", some one can you help me? or tellme why does this happen?
Screen Jbpm console

Answer 1

For this kind of "hello-world" rule, using ruleflow-group is most likely just causing confusion. Do you control when this group is activated? How? - Omitting this rule attribute is indicated.
A rule with an empty left-hand-side will execute only once in a session (as Esteban pointed out).
If you want a rule that fires once for each inserted fact, use
rule "new fact"
when
Object()
then
System.out.println( "new fact inserted" );
end