information retrieval - precision e recall

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Information Retrieval Precision e Recall Appunti sulle metriche 14 Settembre 2007

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Precision e Recall sono due delle metriche utilizzate per misurare le prestazioni di un Sistema di Information Retrieval (recupero delle informazioni). I Motori di Ricerca sono sistemi di Recupero delle Informazioni e quindi possono essere misurati con gli stessi parametri.

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Page 1: Information Retrieval - Precision e Recall

Information Retrieval Precision e Recall

Appunti sulle metriche

14 Settembre 2007

Page 2: Information Retrieval - Precision e Recall

(1)

Definizioni

)(_

)(_

collezionenellapertinentidocumentirelDoc

queryladoporecuperatidocumentiretDoc

relDoc

relDocretDocrecall

retDoc

relDocretDocprecision

_

__

_

__

Page 3: Information Retrieval - Precision e Recall

(2)

Definizioni

Collezionedoc_relDocumenti pertinenti alla query

doc_retDocumenti recuperati dopo la query

precision =

recall =

Page 4: Information Retrieval - Precision e Recall

(3)

e il Web?

Internetpagine_web_relPagine web pertinenti alla query

pagine_web_retPagine Web recuperate dopo la query

Page 5: Information Retrieval - Precision e Recall

(4)

Un buon motore è…

Internetpagine_web_relPagine web pertinenti alla query

pagine_web_retPagine Web recuperate dopo la query

Come si stabilisce la pertinenza di una pagina Web?

Le metriche basse sono solo responsabilità degli algoritmi di recupero delle informazioni dei Motori?

Page 6: Information Retrieval - Precision e Recall

(5)Come si stabilisce la pertinenza di una pagina Web?

Internet

pagine_web_retPagine Web recuperate dopo la query

Un meccanismo di punteggio potrebbe creare un insieme di pagine web rilevanti più affidabile (probabilmente a cardinalità più bassa) con un conseguente aumento della recall.

pagine_web_relPagine web pertinenti alla query

Page 7: Information Retrieval - Precision e Recall

(6)Le metriche basse sono solo responsabilità degli algoritmi di recupero delle informazioni dei Motori?

Internet

Un migliore copywriting e una maggior cura nell’uso dei meta tag potrebbe far accrescere il numero delle pagine Web recuperate ed un conseguente aumento della precision.

pagine_web_relPagine web pertinenti alla query

pagine_web_relPagine web pertinenti alla query

pagine_web_retPagine Web recuperate dopo la query

Page 8: Information Retrieval - Precision e Recall

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