Same answer: most of the time, it is better to have it as a fact, but sometimes, a from may be better by limiting your search space.
Again, these things are like SQL. You need to look at the whole domain model as well as the set of your rules. The major performance optimizations are made on a rule-set level, not individual rules. So, if you want the best performance you need to write your individual rules to work better as a set of rules, sharing nodes, reducing partial matches, etc.
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Edson
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Edson Tirelli
JBoss Drools Core Development
JBoss, a division of Red Hat @ www.jboss.com