final NotDescr not = (NotDescr) rule.getLhs().getDescrs().get( 1 );
pattern = (PatternDescr) not.getDescrs().get( 0 );
final FieldConstraintDescr fld = (FieldConstraintDescr) pattern.getConstraint().getDescrs().get( 0 );
final VariableRestrictionDescr boundVariable = (VariableRestrictionDescr) fld.getRestrictions().get( 0 );
assertEquals( "type",
fld.getFieldName() );
assertEquals( "==",
boundVariable.getEvaluator() );
assertEquals( "$likes",
boundVariable.getIdentifier() );
}