Evaluating Multi-Dimensional Cumulated Utility in Information Retrieval

Traditional Information Retrieval (IR) effectiveness metrics assume that a relevant document satisfies the information need as a whole. Nevertheless, if the information need is faceted or contains subtopics, this notion of relevance cannot model documents relevant only to one or a few subtopics. Furthermore, faceted documents in a ranked list may focus on the same subtopics, and their content may overlap while neglecting other subtopics. Hence, a search result, where topranked documents deal with different subtopics should be preferred over a result where documents are thematically limited and provide overlapping information. The Multi-Dimensional Cumulated Utility (MDCU) metric, recently formulated theoretically by Järvelin and Sormunen, extends the evaluation of novelty and diversity by considering content overlapping among documents. While Järvelin and Sormunen described the theory of MDCU and illustrated its application on a toy example, they did not investigate its empirical use. In this paper, we show the practical feasibility and validity of the MDCU by applying it to publicly available TREC test collections. Furthermore, we analyse its relation with the well-established α-nDCG, and finally, we provide a Python implementation of the MDCU, fostering its adoption as an evaluation framework. Our results indicate a positive correlation between α-nDCG and MDCU, suggesting that both measures correctly identify similar trends when evaluating the IR systems. Finally, compared to α-nDCG, MDCU exhibits a stronger statistical power and identifies up to 9 times more statistically significantly different pairs of systems.