University of Virginia, Department of Computer Science
CS655: Programming Languages, Spring 2000
Manifest: Thursday 2 March 2000
Readings
No new readings. Read Necula & Lee paper before Tuesday
(see 29 Feb Manifest).
Questions
- What are the comparative advantages and disadvantages of axiomatic semantics, operational semantics and static semantics?
- How to use axiomatic semantics to find the weakest pre-condition for some post-condition and code.
- What is the difference between partial correctness and total correctness?
- How to do a total correctness proof for a simple while loop.
Useful Proof Methods
Proof by intimidation: "Trivial" or "obvious."
Proof by exhaustion: An issue or two of a journal devoted to your proof is useful.
Proof by omission: ``The reader may easily supply the details'', ``The other 253 cases are analogous''
Proof by obfuscation: A long plotless sequence of true and/or meaningless syntactically related statements.
Proof by funding: How could three different government agencies be wrong?
Proof by lack of funding: How could anything funded by those bozos be correct?
Proof by democracy: A lot of people believe it's true: how could they all be wrong?
Proof by reference to inaccessible literature: The author cites a simple corollary of a theorem to be found in a privately circulated memoir of the Icelandic Philological Society, 1883. This works even better if the paper has never been translated from the original Icelandic.
Proof by forward reference: Reference is usually to a forthcoming paper of the author, which is often not as forthcoming as at first.
Proof by flashy graphics: A moving sequence of shaded, 3D color models will convince anyone that your object recognition algorithm works. An SGI workstation is helpful here.
Proof by vehement assertion: It is useful to have some kind of authority relation to the audience, so this is particularly useful in classroom settings.
Proof by vigorous handwaving: Works well in a classroom, seminar, or workshop setting.
Proof by cumbersome notation: Best done with access to at least four alphabets, special symbols, and the newest release of LaTeX.
Proof by lack of space:
"The proof is not detailled due to lack of space in this proceedings..." works well in conjunction with proof by forward reference.
Selected from http://www.ai.sri.com/~luong/research/proof.html.
None of these proof methods are suggested in your problem sets or project reports.
