¹Department of Design and Use of Information Technology, IT University of Copenhagen, Copenhagen S, Denmark

Correspondence: Dixi Louise Strand, Department of Design and Use of Information Technology, IT University of Copenhagen, Rued Langgaards Vej 7, 2300 Copenhagen S, Denmark. Tel: +45 72185162; Fax: +45 72185001; E-mail: dixi@itu.dk; URL: www.itu.dk/people/dixih

Received 5 August 2005; Revised 24 September 2005; Accepted 28 September 2005.