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Wildcard queries

Wildcard and vector space queries require different indexes, except at the basic level that both can be implemented using postings and a dictionary (e.g., a dictionary of trigrams for wildcard queries). If a search engine allows a user to specify a wildcard operator as part of a free text query (for instance, the query rom* restaurant), we may interpret the wildcard component of the query as spawning multiple terms in the vector space (in this example, rome and roman would be two such terms) all of which are added to the query vector. The vector space query is then executed as usual, with matching documents being scored and ranked; thus a document containing both rome and roma is likely to be scored higher than another containing only one of them. The exact score ordering will of course depend on the relative weights of each term in matching documents.

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