Logic Puzzle Solver

To solve a puzzle like this you need the following diagram. Fill in a "+" if you know that something is for sure and a "-" if you know for sure something is not true.
For example: The Englishman lives in the red house. So at the cross English-Red write a "+". And on the crosses English-Green,-White,-Yellow,-Blue you write a "-". Because you know that the Englishman doesn't live in one of the other houses.