Figure 9.

Procedure of recursive re-ranking. A recursive re-ranking algorithm is called for the phase of re-ranking in the section of the factor analysis based algorithm. The recursive division divides the passages into the base cases, according to the sorted term association, which is very similar to a binary tree. For example, the factor analysis based model gives a ranking list of terms as {T1, T2, T3} for re-ranking. The baseline results are then first re-ranking by T1, where <a onClick="popup('http://www.biomedcentral.com/1471-2105/13/S9/S2/mathml/M43','MathML',630,470);return false;" target="_blank" href="http://www.biomedcentral.com/1471-2105/13/S9/S2/mathml/M43">View MathML</a> are results containing T1 and <a onClick="popup('http://www.biomedcentral.com/1471-2105/13/S9/S2/mathml/M44','MathML',630,470);return false;" target="_blank" href="http://www.biomedcentral.com/1471-2105/13/S9/S2/mathml/M44">View MathML</a> are results not containing T1. Second, <a onClick="popup('http://www.biomedcentral.com/1471-2105/13/S9/S2/mathml/M45','MathML',630,470);return false;" target="_blank" href="http://www.biomedcentral.com/1471-2105/13/S9/S2/mathml/M45">View MathML</a> and <a onClick="popup('http://www.biomedcentral.com/1471-2105/13/S9/S2/mathml/M46','MathML',630,470);return false;" target="_blank" href="http://www.biomedcentral.com/1471-2105/13/S9/S2/mathml/M46">View MathML</a> are recursively re-ranked by T2. <a onClick="popup('http://www.biomedcentral.com/1471-2105/13/S9/S2/mathml/M47','MathML',630,470);return false;" target="_blank" href="http://www.biomedcentral.com/1471-2105/13/S9/S2/mathml/M47">View MathML</a> are the results containing T2 and T1, while <a onClick="popup('http://www.biomedcentral.com/1471-2105/13/S9/S2/mathml/M48','MathML',630,470);return false;" target="_blank" href="http://www.biomedcentral.com/1471-2105/13/S9/S2/mathml/M48">View MathML</a> are those not containing T2 but containing T1. <a onClick="popup('http://www.biomedcentral.com/1471-2105/13/S9/S2/mathml/M49','MathML',630,470);return false;" target="_blank" href="http://www.biomedcentral.com/1471-2105/13/S9/S2/mathml/M49">View MathML</a> are the results containing T2 but not containing T1, while <a onClick="popup('http://www.biomedcentral.com/1471-2105/13/S9/S2/mathml/M50','MathML',630,470);return false;" target="_blank" href="http://www.biomedcentral.com/1471-2105/13/S9/S2/mathml/M50">View MathML</a> are those not containing T2 and T1. Similarly, <a onClick="popup('http://www.biomedcentral.com/1471-2105/13/S9/S2/mathml/M51','MathML',630,470);return false;" target="_blank" href="http://www.biomedcentral.com/1471-2105/13/S9/S2/mathml/M51">View MathML</a>(i = {1, 2, 3, 4} are re-ranked by T3 at the third step.

Hu et al. BMC Bioinformatics 2012 13(Suppl 9):S2   doi:10.1186/1471-2105-13-S9-S2