Whenever we query a document set, we might retrieve irrelevant documents or miss relevant ones. Typically, as precision increases, recall decreases and vice versa. If we want to improve both precision and recall, we must use more sophisticated techniques. In the remainder of this talk, I will focus on these three techniques. Most of the major commercial text search engines now use sophisticated and fast word analysis, which reduce the chances of mismatching words.
Words often have multiple meanings, which can only be distinguished by context.
Adding words to the query improves the relevance of the results. The reference document will have other words related to cats and the result of the augmented query will be more relevant. These words can be used to cluster the documents into separate groups so that the user can easily indicate which groups are of interest. Sophisticated linguistic analysis can improve precision. Document structure can be used to emphasize and de-emphasize some words.