Recent research directions in automated timetabling Edmund Kieran Burke, Sanja Petrovic Automated Scheduling, Optimisation and Planning (ASAP) Research Group, School of Computer Science and Information Technology, University of Nottingham, Jubilee Campus, Nottingham NG8 1BB, UK Abstract The aim of this paper is to give a brief introduction to some recent approaches to timetabling problems that have been developed or are under development in the Automated Scheduling, Optimisation and Planning Research Group (ASAP)attheUniversityofNottingham.Wehaveconcentrateduponuniversitytimetablingbutwebelievethatsome of the methodologies that are described can be used for different timetabling problems such as employee timetabling, timetablingofsportsfixtures,etc.Thepapersuggestsanumberofapproachesandcomprisesthreeparts.Firstly,recent heuristic and evolutionary timetabling algorithms are discussed. In particular, two evolutionary algorithm develop- ments are described: a method for decomposing large real-world timetabling problems and a method for heuristic initialisation of the population. Secondly, an approach that considers timetabling problems as multicriteria decision problems is presented. Thirdly, we discuss a case-based reasoning approach that employs previous experience to solve new timetabling problems. Finally, we outline some new research ideas and directions in the field of timetabling. The overallaimoftheseresearchdirectionsistoexploreapproachesthatcanoperateatahigherlevelofgeneralitythanis currently possible. Ó 2002 Elsevier Science B.V. All rights reserved. Keywords: Combinatorial optimisation; Timetabling/Scheduling; Meta-heuristic approaches; Multiple criteria analysis; Case-based reasoning; Hyper-heuristics 1. Introduction Educational timetabling is a major administra- tive activity for a wide variety of institutions. A timetabling problem can be defined to be the problem of assigning a number of events into a limited number of time periods. Wren (1996) de- fines timetabling as follows: ‘‘Timetabling istheallocation,subjecttocon- straints, of given resources to objects being placedinspacetime,insuchawayastosat- isfyasnearlyaspossibleasetofdesirableob- jectives.’’ In this paper, we will concentrate on university timetabling problems. Such problems can be di- videdintotwomaincategories:coursetimetabling and exam timetabling. These problems are subject to many constraints that are usually divided into two categories: ‘‘hard’’ and ‘‘soft’’ (e.g., Burke et al., 1997). Hardconstraintsarerigidlyenforced.Examples of such constraints are: • Noresource(studentsorstaff)canbedemanded tobeinmorethanoneplaceatanyonetime. European Journal of Operational Research 140 (2002) 266–280 www.elsevier.com/locate/dsw E-mail addresses: ekb@cs.nott.ac.uk (E.K. Burke), sxp@cs. nott.ac.uk (S. Petrovic). 0377-2217/02/$ - see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII:S0377-2217(02)00069-3