1. A method for allowing a content-based search of a data archive for files and for image files referenced by the files, the method comprising: extracting features from a number of files managed by a document management system in an image retrieval system, to produce an inverted index including elements of at least two attributes and context information held in the files and used for content-based image retrieval; and executing a parsing algorithm and an algorithm for extracting features of at least one of new files and ones of the files whose content has been at least one of extended and altered when the files are stored in a data archive managed by the document management system for the purpose of updating the inverted index.