Hello, we designed a clever visualization of logical expressions once. Imagine a a huge pile of sand we poured into a vertical flow of sieves. The sand is the set that is to be filtered. The sieves are the conditions. At each sieve the amount of grains is reduced. When there is an OR-path, the flow forks and of course it lets more grains of sand through. This way the sand ripples down from top to bottom and in the end you have your final set. Sounds really colourful, eh? When you design it, it looses a lot of the original metaphor. But it works astonishingly. We made people create complex filters who usually have problems using google. I can send you a wireframe if you're interested.

Jan