contradicting is a reciprocal relationship between Facts that are defined to contratdict each other. The library cannot determine which these are, so only provides the bare framework here. Game code then needs to define which facts oontradict by listing them on the contradicting relation's relTab property, e.g. *.
relTab = [
'lisbon-capital' -> ['madrid-capital'],
'jumping-silly' -> ['jumping-healthy']
]

contradicting :   Relation