1 / 9

Thesaurus Creation/ Term Clustering

Thesaurus Creation/ Term Clustering. Two major applications: Query expansion – fleshing out sparse queries with related words improves recall (at possible expense of reduced precision) Termset dimensionality reduction Similar outcome with smaller model.

cdunlap
Download Presentation

Thesaurus Creation/ Term Clustering

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Thesaurus Creation/Term Clustering Two major applications: • Query expansion – fleshing out sparse queries with related words • improves recall (at possible expense of reduced precision) • Termset dimensionality reduction Similar outcome with smaller model

  2. 1 0 0 1 0 0 0 0 Term Dimensionality Reduction Query : Water Spaniel Diseases Spaniel Spaniels disease diseases collie illness ant Original vector VQ Reduced vector VQ’ DOG ILL INSECT 0 1 1 • Collie illnesses • Poodle sickness Problem : Reduced flexibility in partial weighting of synonym set  Synonyms got as much weight as the original • Equivalent to query expansion when i for all synonyms is 1

  3. 1 1 1 0 0 0 0 0 Query Expansion Query : Water Spaniel Diseases Original syn Expanded 1 1 1 1 23 4 0 Water Spaniel diseases Spaniels diseases illness collie ant stem   i  semantic dist(wi ,t) Relate Document set: D1 : Water Spaniels D2 : Water Spaniel illnesses D3 : Collie diseases stem syn syn

  4. Query Expansion Query : Water Spaniel diseases document1 : … water spaniels ….. …

  5. Simplest Term Clustering  Stemming is a clustering method stemming Original Term SetClustered Term Set computing flies computers houses computation flown compute flew house comput * fly *

  6. Another simple clustering method: Pre-existing thesauri(e.g. Rogets’) different pos illness  disease, sickness, unwell, sick, ill, … PhD  Ph.D, PhD, Phd, Ph.D., …. Term equivalence classes Loosely related topic sets DOG  Spaniel, Collie, Schunauzer, bulldog, Poodle, …. same part of speech(pos)

  7. Term Clustering Non-hierarchical methods : single pass(Salton, ’71) • Given clustering threshold/target size and similarity function sim(i , j ) •  Pick random document Dj • Assign a document di : sim(Dj , dj) <  to cluster Cj and recalc centroid else create a new cluster Ck with centroid dk •  Exclude di from document list •  Repeat until document list empty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D2 . . .  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D1 . . . . . . . . . . . . . . .  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

  8. Types of Clustering Behavior/Criterion Sim(ti , tj) Document level – co-occurrence in same document Verb-object Syntagmatic similarity sim(drink, wine) appears together sim(eat, meat) in region sim(drink, water) Paradigmatic similarity sim(wine, water) appears as objects sim(wine, drink) of the same verb sim(wine, meat) based on object of drink or of all verbs  

  9. N-gram Syntagmatic similarity sim(Hong, Kong) occur together sim(soap, opera) sim(soap, suds) Paradigmatic similarity sim(opera, suds) occur in same sim(tall, short) context sim(long, short) sim(Hong, Kong)  soap opera suds residue Ivory soap Dial Lye

More Related