To: Eric Bloedorn, Ibrahim Imam, Ken Kaufman, Mark Maloof, Ryszard Michalski, and Janusz Wnek, of The George Mason University East-West Challenge Group From: Donald Michie 5 Oct Dear colleagues David showed me your extremely interesting message. Both your points are in our view valid. Indeed I see one of them, to do with the discrepancy between "P-complexity" and true cognitive complexity, as central to the whole ML enterprise. How nice when we can replace Minimal Description Length with Minimal Cognitive Load as a driving principle in our ML algorithms! Meanwhile we used the best we had as a measuring stick. I discuss the issue towards the end of my article on Competition 1, which will appear in Computing on 20 October. The full text is in the file michie.txt, and gives details of the part of this competi- tion that was attacked by unaided human brains, 42 of them in this case, after subtracting frivolous entries. It also announces that for Computing readers the present competition is to become the first of a regular series, held every two months (see closing passage of accompanying document). This interest shown by the editors of Computing came as a pleasant surprise. Overseas readers can enter by email. To get the text of my articles alter- nately setting and assessing successive Trains competitions you'll need to get onto Computing's mailing list (their email is "computed@cix.compulink.co.uk". I'll keep you posted with my own email address. In fairness to Bernhard Pfahringer, I should add my view that, given the game rules, his was an exceptionally impressive effort, well deserving of the prize. As stated in the accompanying docu- ment, for future competitions I shall base complexity scoring on Trenglish, which has now, I believe, evolved into a sufficiently mature and versatile formal language to take the strain. This is essentially Janusz Wnek's " ... number of words in simply expressed and grammatically correct English sentences represent- ing condition parts of the rules". On your second point concerning Competition 2, you appear to have proved a (to us) unwelcome theorem, to the effect that anyone who has submitted to Competition 1 a rule that scores in the lower quartile of Trolog scores can automatically secure full marks for Competition 2 simply by declaring in his/her submission of his 50-train labelling that he/she wishes the said rule to be used as oracle in assessing the labelling. Having actually used this rule to assign the labels, he will be assured of a 100% correct score! More than one reader used this tactic, so a tie-break was applied (see Ashwin Srinivasan's note in the accompanying materials briefly reporting on Competitions 1, 2 and 3). The cause of our slip-up was an unexamined assumption that the intersection of Competition 1 entrants and Competition 2 entrants would be empty. The assumption was of course unwarranted. David Page is circulating this message and its appended article to AI Comp and ML List, together with Ashwin's report on Competi- tions 1, 2 and 3. Donald Michie. 6 Oct 94