6. A document management and retrieval method, comprising: a document index creating step of storing appearance positions of a plurality of words contained in one or more of a plurality of documents; a tag storing step of storing a plurality of tag indexes and an appearance position of each tag in a set of documents of the plurality of documents, each tag index being associated with a respective character string and comprising: a tag associated with its respective character string in one of the plurality of documents, the tag having a tag name and indicating attributes of the character string based upon the meaning of the character string; at least one of a right word string comprising one or more adjacent words that appears to the right of its respective character string and a left word string comprising one or more adjacent words that appears to the left of its respective character string; a combination of the tag with at least one of the left and right word strings; and storing an appearance position of the character string associated with each tag in a set of documents of the plurality of documents; a document retrieval step of receiving as a search query an input of a phrase containing a search tag name and a search word, and returning a list of identified documents that contain the phrase by utilizing the combination entries stored in the tag index store; and using a high-frequency word and a tag name to store a bit string representing a set of documents that contain the high-frequency word and a bit string representing a set of documents that contain a tag, wherein: the tag update step includes updating a bit string in a bit string store based on a tag that has been added or removed through a tag update; and the document retrieval step includes referring to bit strings that have been stored in the bit string storing step with a high-frequency word and tag name contained in the search query, obtaining data representing a set of documents that contain all high-frequency words and tags in the search query, and reading word appearance positions and tag appearance positions in the set of documents of the plurality of documents.
8. The document management and retrieval method of claim 6 , wherein the attribute indicated by at least one of the tags is one of a person's name, a company name and a location name.