Keynote by Prof. Dr. Pertti Vakkari
In evaluating search systems there is a growing trend to complement the established effectiveness indicator topical relevance by the usefulness of search results. Usefulness refers to the contribution of search results to a larger task generating information search. Task outcome signifies the end-product of a task performance process. It is evident that the whole search process contributes to task outcome. The aim of my presentation is to give a systematic account of the characteristics and results of studies focusing on the usefulness of search results or task outcomes in larger tasks containing searching. I summarize how the usefulness of search results, and search outcomes are defined and operationalized in empirical studies. I categorize various types of usefulness and outcomes and various predictor types used in studies. Finally, I summarize which factors significantly predict the usefulness of search results as well as search outcomes.