17、概率索引：快速有效的信息检索及其实验验证

概率索引：快速有效的信息检索及其实验验证

基于字符格的单词位置索引

在信息检索中，构建单词的顺序位置概率索引（PrIx）是一项重要任务。我们可以将各个步骤整合起来构建顺序位置 PrIx。下面的算法描述了基于字符格计算单词顺序位置 PrIx 的过程：

Algorithm 5.16 Compute a word ordinal position PrIx based on a character lattice.
Require: A compact lattice 퐴 = (Σ, Q, E, 푞0, 흔) of an image 푥
Require: A function Λ(·) which assigns a class to each character label
Require: A function Δ which determines whether a character class is or is not a word separator
Require: The maximum number of words to index, 푛
1: procedure LatticeCharacterIndexPosition(퐴, Λ, Δ, 푛)
2:     휷 ← Backward(퐴)
3:     푇 ← LatticeDisambiguateInputClass(퐴, Λ)
4:     푇 ← LatticeDisambiguateWordCount(푇, Δ)
5:     푇 ← LatticeEncodeWordCount(푇)
6:     푇 ← LatticeConvertSubToComple