A (failing) attempt to get Euler to compute something

I was trying out Euler.

 created the attached file (factorial.n3)
running cwm factorial.n3 --think --data --purge gives me

    0     :factorial 1 .

    1     :factorial 1 .

    2     :factorial 2 .

    3     :factorial 6 .

    4     :factorial 24 .

    5     :factorial 120 .

    6     a :Question;
         :factorial 720 .

    720     a :Answer .


I can't figure out how to get Euler to compute factorial for me.
I try
/usr/java/jdk1.5.0/bin/java Euler /home/syosi/program/factorial.n3 
/home/syosi/program/q.n3

and it tells me

# Generated with http://www.agfa.com/w3c/euler/ version R4043 on 25 Nov 
2004 19:35:12 GMT
@prefix log: <http://www.w3.org/2000/10/swap/log#>.

(<file:/home/syosi/program/factorial.n3>.log:semantics).log:conjunction =>
{
# No proof found for file:/home/syosi/program/q.n3 in 123 steps (453 
steps/sec) using 1 engine (7 triples)
}.

No matter what I try, it tells me no proof found. What am I not doing?


Yosi

@prefix log: <http://www.w3.org/2000/10/swap/log#> .
@prefix math: <http://www.w3.org/2000/10/swap/math#> .
@prefix : <http://yosi.us/math#> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .



{ ?x a :Number;
     math:equalTo 0 . }
log:implies
{?x :factorial 1 . } .



{ ?x a :Number .
(?x -1) math:sum ?z .
 ?z :factorial ?a .
 (?a ?x) math:product ?y .}
log:implies
{?x :factorial ?y} .

{ ?x a :Number .
 (?x -1) math:sum ?z . 
 ?z math:notLessThan 0}
log:implies
{?z a :Number} .

{?x a :Question} log:implies {?x a :Number} .

{?x a :Question;
 :factorial ?y . }
log:implies
{?y a :Answer . } .

:Number a log:Chaff .

6 a :Question .

@prefix : <http://yosi.us/math#> .

_:x a :Answer .