The Query Understanding Pipeline (QU) is the front-end NLP intelligence hub of search engines and e-commerce portals that structurally decodes raw search intents within
<5ms before physical indexing: 1) Normalization (punctuation stripping, case folding, unicode normalization); 2) Spelling Correction (edit distance, phonetic pinyin mapping, and n-gram LM correction); 3) NER & Term Weighting (extracting brands, categories, attributes, and computing information entropy weights); 4) Synonym Expansion & Rewriting (e.g., expanding 'Apple phone' to 'iPhone'); 5) Intent & Category Classification (predicting transactional, navigational, or informational categories with confidence logits).