A document management method uses a plurality of document schemas to manage a document retrieval request, the document schemas defining a structure of document contents, each document schema including a plurality of attributes. In the document management method, a schema identifier is assigned to each of the plurality of document schemas by generating a global unique identifier value every time a schema name of a new document schema is input. An attribute identifier is assigned to each of the plurality of attributes of one of the plurality of document schemas by generating another global unique identifier value.