Upweighting document zones.

In text classification problems, you can frequently get a nice boost to effectiveness by differentially weighting contributions from different document zones. Often, upweighting title words is particularly effective (Cohen and Singer, 1999, p. 163). As a rule of thumb, it is often effective to double the weight of title words in text classification problems. You can also get value from upweighting words from pieces of text that are not so much clearly defined zones, but where nevertheless evidence from document structure or content suggests that they are important. Murata et al. (2000) suggest that you can also get value (in an ad hoc retrieval context) from upweighting the first sentence of a (newswire) document.