Providing a new model for the distance between query words based on the minimal displacement

Based on the researches performed on search engines, most user queries contain more than one word. For queries with more than one word, two models can be presented. In the first model, query words are assumed to be independent of each other, and in the second model, the place and the order of words are assumed to be dependent. Experiments show that there are dependencies among most query words. One of the parameters that can determine the dependency between query words is the distance between the query words in the document. In this paper, a new distance definition based on the minimum displacement of the document words in order to match the query is presented. Also, given that most ranking algorithms use the word frequency in the documents (Term Frequency) to score the documents and since there is no clear definition for this parameter for queries with more than one word; in this paper, the frequency of the occurrence of a phrase (Phrase Frequency) and Inverted Document Frequency are defined according to the new concept of distance and the proper algorithms are presented to calculate them. Also, the results of the proposed algorithm are compared with the algorithm implemented by the open source Lucene indexer, which shows a good increase in the mean accuracy