bash-3.2$ des
*********************************************************
*                                                       *
*        DES: Datalog Educational System v.3.0          *
*                                                       *
* Type "/help" for help about commands                  *
*                                                       *
*                    Fernando Saenz-Perez (c) 2004-2012 *
*                                         GPD DISIA UCM *
*             Please send comments, questions, etc. to: *
*                                     fernan@sip.ucm.es *
*                                             Web site: *
*                           http://des.sourceforge.net/ *
*                                                       *
* This program comes with ABSOLUTELY NO WARRANTY, is    *
* free software, and you are welcome to redistribute it *
* under certain conditions. Type "/license" for details *
*********************************************************

DES> /c hw4-EC-family.dl 

Info: 33 rules consulted.

DES> brother(X,Y)

{
  brother(bernhard,karl),
  brother(franz,heinz),
  brother(franz,hermann),
  brother(heinz,franz),
  brother(heinz,hermann),
  brother(hermann,franz),
  brother(hermann,heinz),
  brother(karl,bernhard),
  brother(kati,bernhard),
  brother(kati,karl)
}
Info: 10 tuples computed.          

DES>