Actually I'm not sure how complicated your clauses can become, I'm a bit too busy to dive in now.

But the example given in the OP should be solvable by filling 3 zeros for each clause and applying simple deduction rules on the 3x3 cuts.

I think the strength of prolog comes to play if you apply more complicated rules.

Please don't take this as a critic of your work, just theoretical observations. :)

update

Applying the rules given on a 3x3x3 matrix displayed by 3 cuts by name:

• like The one who likes apples is not a blacksmith => 3 zeroes at (apple&blacksmith) x names.
• and so on:

FRUITS   PROFESSIONS NAMES

            W B F   
pineapples  
apples        0 0    John
pears       0 0 0

pineapples  0
apples      0 0 0    Patrick
pears       0

pineapples  0 0 0
apples      0 0 0    James
pears           0
[download]

Deductions:

• The apple cut has only one free field
• => John is a witcher who likes apples
• All free fields in the witcher and John cut must be filled with zeroes.

FRUITS   PROFESSIONS NAMES

            W B F   
pineapples  0 0 0
apples      1 0 0    John
pears       0 0 0

pineapples  0
apples      0 0 0    Patrick
pears       0

pineapples  0 0 0
apples      0 0 0    James
pears       0   0
[download]

Deductions:

• The James cut has only one field free
• => James is a blacksmith who likes pears.
• the remaining fields in blacksmith and pears cut are filled with zeroes.

FRUITS   PROFESSIONS NAMES

            W B F   
pineapples  0 0 0
apples      1 0 0    John
pears       0 0 0

pineapples  0 0
apples      0 0 0    Patrick
pears       0 0 0

pineapples  0 0 0
apples      0 0 0    James
pears       0 1 0
[download]

• Only one field free
• => Patrick is a fisherman who like pineapples.

I did it manually, hope everything is right and I made the technique of a solver clearer.

I think you need more complicated rules to challenge people and take advantage of the power of prolog. :)