Abstract
Design patterns are acknowledged as powerful conceptual tools to improve design quality and to reduce the time and cost of design by effect of the reuse of "good" solutions. In many fields such as software engineering, web engineering, and interface design, patterns are widely used by practitioners and are also investigated from a research perspective. Still, the concept of design pattern has received marginal attention in the arena of user interfaces (UIs) for Recommender Systems (RSs). To our knowledge, a little is known about the use of patterns in this specific class of applications, in spite of their increasing popularity, and no RS specific interface pattern is available in existing pattern languages. We have performed a systematic analysis of 28 real-world RSs in a variety of sectors, in order to: (i) discover occurrences of existing general (i.e., domain independent) UI patterns; (ii) identify recurrent UI design solutions for RS specific features; (iii) elicit a set of new UI patterns for RS interfaces. The analysis of patterns occurrences highlights the degree at which "good" UI design solutions are adopted in RSs for the different sectors. The new patterns can be used by UI designers of RSs to improve the UX of their systems.