gh@utai.UUCP (Graeme Hirst) (10/25/84)
COLLOQUIUM Department of Computer Science, University of Toronto 11:00, Tuesday 30 October 1984, Sandford Fleming 1105 Helping the Lost and Confused: Computer Retrieval of Books and Maps Michael Lesk Bell Communications Research Murray Hill, NJ What good does it do to have lots of information in machine-readable form if you can't access it? Two experi- ments addressing this issue will be discussed. In one, Mur- ray Hill library users chose between a keyword and menu user interface to an on-line catalog, and in the other people got driving directions from a computer. (1) For two years, the Murray Hill library has had an on-line public catalog, which was installed to see whether the customers would prefer a keyword retrieval system, in which they type author names, subject words, etc., or a menu system, in which they chose subject categories from the Dewey hierarchy. Conventional wisdom (e.g., in the design of Prestel) is that users would rather choose from alterna- tives, not name things. Our naive library users, contrary to the literature recommendations, preferred the keyword search system. We suggest deep menus are not appropriate when users already have a good idea what they want. (2) A machine-readable street map was the basis of the second experiment, an attempt to give computerized driving directions. This combined an interesting theoretical prob- lem (shortest path in a graph), an interesting database problem (storing a planar graph of 100,000 nodes and 150,000 edges, with fast retrieval needed by edge name, node loca- tion, and connectivity), and a chance to be energy-efficient (4% of the gasoline used in the UK is wasted, either by drivers who are totally lost or just taking an inefficient route). We investigated various search algorithms for find- ing map routes, including breadth-first and depth-first search. Either distance or time can be minimized. We've found that merely shortest distance produces complex and inappropriate routes; at least there must be a charge for making turns. Two-directional depth-first search was gen- erally good, but it's not what people use: they employ a variant of divide-and-conquer. -- \\\\ Graeme Hirst University of Toronto Computer Science Department //// utcsrgv!utai!gh / gh.toronto@csnet-relay / 416-978-8747