E-Commerce

Can a Recommender System induce serendipitous encounters? 239bots, which captured information from the official website 2 of the Vatican picture-gallery. Inparticular, for each element in the dataset an image of the artefact and three textualmetadata (title, artist, and description) were collected. Fig. 6 shows a sample of the resultingitem. All artworks were laid in the schematic environment model of the Pinacoteca in orderto deal with the spatial layout influence on recommending.Fig. 6. Sample of dataset itemWe involved 30 users who voluntarily took part in the experiments. The average age of theusers was in the middle of twenties. None of the users was an art critic or expert. Users wererequested to express their preferences for collection items as a numerical vote on a 5-pointscale (1=strongly dislike, 5=strongly like).The ratings have been used for K-fold cross validation (Kohavi, 1995) that gave back anaverage degree of precision, recall and F-measure (Herlocker et al., 2004). We simulated theuser interaction with the system using a small part of the ratings of each user for the training ofthe classifier. Then five iterations were performed, in which a serendipitous item was selectedby the module, rated with the ratings already expressed and added to the training set. Theratings for 5 serendipitous items proposed to each one of the 30 users were collected. Thewhole process has been done with the most serendipitous function and for the random overmost serendipitous function with a numeric threshold of 5%, 10% and 15% of the database.Investigating different strategy to provide serendipitous recommendation, the ratinginterpretation issue comes out. Indeed, from a pragmatic point of view, ratings must behomogenous with other ratings in order to allow their subsequent exploitation in the profilelearning step, but user rating motivations affect the meaning evaluation of finding unknownand possibly interesting things, and not simply interesting ones. For instance, a poorlyrating for serendipitous suggested items should come from the experience of the user (theuser already knows the item), from her lack of interest (the user already knows the item andis not interested in it), from her lack of interest in finding new things (the user does notknow the item and has no interest in knowing something new), from the consciousexpression of dislike (the user did not know the item before, now she knows it but she does2 http://mv.vatican.va/3_EN/pages/PIN/PIN_Main.html