1. 1There are two kinds of relevance, user‐oriented and machine (system) oriented. Here, we consider the latter.
2. 2The first 10 results recalled by SE.
3. 3Number of SEs.
4. 4Number of keywords.
5. Barker, J. (2004), “Meta‐search engines”, Teaching Library Internet Workshops, University of California, available at: www.lib.berkeley.edu/TeachingLib/Guides/Internet/Metasearch.html (accessed March 4 2006)