Let S be a compact complex surface of general type, Smin its minimal model gotten by contracting the finite number of (−1)-curves. It is a smooth surface with nef canonical line bundle KSmin . It then can be shown that Smin has at most b2 curves on which the canonical line bundleKSmin restricts to a non-ample bundle (i.e. whose intersection number with KSmin is non positive). These are (−2) smo...

It has been conjectured [Blair] that every definite clause logic program containing exactly one rule is canonical. This note presents a simple proof