"The search process was explained very clearly as a Venn diagram. I am looking for 'this AND (this OR this) but NOT this'."

Exactly! Very powerful tool for most forms of data analysis.

Funny you should mention it, Jeanie, but while trying to remember some old symbolic logic (a PhD quoted on another thread fell into the trap of using false syllogisms), I came across this website. Note that at one point it explains the whole in Venn diagrams!

Categorical Syllogisms