Gladly.  I won't spoil the problem for you by giving you a solution, but I'm happy to help you work your way toward it.

Start by asking yourself several questions:

• How could you represent an n-by-n chessboard in Alloy?


• Given a representation for the board, how could you represent the presence of a queen in a given square?

Once you have these preliminary decisions out of the way, you can go on to the crucial questions:

• Given a representation for the presence of queens in particular squares, how do you ensure that no two queens are in the same square?


• And (more important) how do you tell whether one queen threatens another queen, in this representation?

Unless you are smarter than I am, you may find that your first answers to the first set of questions make it harder than you'd like to formulate answers to the second set of questions.  So in the course of answering the second set of questions, you may find yourself going back and changing your answers to the first set.  This is normal and should not discourage you.

I hope this helps.

--C. M. Sperberg-McQueen
  cmsmcq@blackmesatech.com
  http://cmsmcq.com/mib

Thanks for your help.