I listened to a radio program on the subject of trap streets. Fictitious streets, towns and other pieces of geography added to a map made copying detectable, since if the other map had been independently created it could not contain these inventions, a trap. This phenomenon has come into sharp relief because of the rise of computer map systems, either on the web or through satellite based navigation systems (GPS) that have put the details of maps under more scrutiny and daily use.
This is part of a larger tactic of copyright traps in reference works like encyclopedias and trivia books. The story captured my attention, and I am writing about it here, because I am aware of a similar instance in the history of computing. Leslie J. Comrie (1893-1950) was a master maker of mathematical tables, an innovative user of digital calculators and the man who lent Maurice Wilkes his copy of the "First Draft of a Report on the EDVAC". Comrie edited Chamber's Shorter Six-Figure Mathematical Tables (vol. 2, 1949) and in his preface he emphasized the high accuracy of the tables noting "In no case should any greater than +- 0.52 units of the last decimal be found. Moreover, it is confidently believed that the cases where the error exceeds +- 0.51 units of the last decimal could be counted on the fingers of one hand." (p. vii) He then continues: "those that are known to exist form an uncomfortable trap for any would-be plagiarist." (p. vii) So Comrie also participated in this practice of laying traps for the plagiarist.
Comrie's use of this tactic, even as he stakes his claim to accuracy reveals the tension in the creation of these traps. Key to the value of the tables is in their claim to accuracy, but the traps are errors. Comrie's resorting to such a tactic suggests the problems of obtaining recognition and compensation for this sort of intellectual endeavour. I mention recognition because I have to wonder if any fly-by-night plagiarists lacking the imprimature of Chamber's and Comire could really have seriously competed for sales with the original. The advent of high speed computing may have ended the problem of motivating table makers, but the problem of recognition and compensation for intellectual work is perennial.
One more thing, it is not clear how effective copyright traps actually are. In one case a man sued the makers of the Trivial Pursuit game for copying a fictitious entry (the supposed first name of the TV detective Columbo) from his trivia book (and many true entries) into a question and answer for the game. However, the court found that this did not constitute an infringement because the presentation of the (purported) facts differed.