I'm a bit confused by the usage of "percolation". Generally speaking that refers to, in a tiered retrieval system, a document being initially indexed in a smal

I'm a bit confused by the usage of "percolation". Generally speaking that refers to, in a tiered retrieval system, a document being initially indexed in a small temporary index then gradually "percolated" upwards to larger more permanent indices. Such systems allow updates without merging into the main index. See: http://nlp.stanford.edu/IR-book/html/htmledition/dynamic-indexing-1.html http://nlp.stanford.edu/IR-book/html/htmledition/dynamic-ind...