1. Every s ∈ SQ that consists of contiguous query terms is likely to appear as an
exact phrase in a relevant document (i.e., represented using the #od:1 operator).
2. Every s ∈ SQ such that |s| > 1 is likely to appear (ordered or unordered)
within a reasonably sized window of text in a relevant document (i.e., in a
window represented as #uw:8 for |s| = 2 and #uw:12 for |s| = 3 ).
As an example, this model produces the Galago query language representation
shown in Figure 7.6 for the TREC query “embryonic stem cells”, where the
weights were determined empirically to produce the best results.
Given the important pieces of evidence for web search ranking, we can now
give an example of a Galago query that combines this evidence into an effective
ranking. For the TREC query “pet therapy”, we would produce the Galago query
shown in Figure 7.7. The first thing to note about this query is that it clearly shows