However, Harter (1996)
argues that using a fixed set of documents and queries does not reflect reality. In
addition, it is widely accepted that external factors exist that can considerably affect the
retrieval results like query quality and familiarity of search topic (Alemayehu, 2003;
Gao et al., 2004; Harter, 1996). User-centric approaches evaluate users' satisfaction by
viewing the system as a whole and involving the users. Sometimes user satisfaction is
equated with system effectiveness