touches( $geometry , $geometry)
touches( geomFromWKT( 'LINESTRING(5 3 , 4 4)' ) , geomFromWKT( 'LINESTRING(3 3 , 4 4 , 5 5)' )) → returns 1
touches( geomFromWKT( 'POINT(4 4)' ) , geomFromWKT( 'POINT(5 5)' )) → returns 0