Re: [rules-users] Can I solve the 'Zebra Puzzle' in drools?

This puzzle can be solved using forward chaining, i.e., by using Drools or any similar RBS, but it isn't possible by implementing the givens as rules, expecting that an increase in the filled-in values will result in a (the) solution. Certainly, it is possible to write a rule such as rule EnglishRed when $h: House( nationality == null && colour == Colour.RED || nationality == Nationality.ENGLISHMAN && colour == null ) then modify( $h ){ setNationality( Nationality.ENGLISHMAN ), setColour( Colour.RED ) } end which adds "red" or "Englishman" to a House as soon as the other property is present. But this approach comes to a standstill as soon as more sophisticated mental processes are required in the manual solution technique. One approach I've tried successfully is to generate all permutations of animals, colours, drinks, nationalities and smokes (120 each), insert them as facts, and to write one big rule according to the givens. A similar approach uses facts consisting of an attribute indication (animal,... smoke), a value and a reference to a House, again starting with all possible associations and using one rule to select the attribute combinations satisfying the givens. I'm not quite sure how the rules presented by Miles should work, but I don't think that swapping values between House facts is going to work, even when more defensive strategies against looping are employed. -W On 15 June 2011 14:47, FrankVhh <frank.vanhoenshoven(a)agserv.eu&gt; wrote: