But locating documents of interest can be difficult. This imposes a resource burden on the central site, and makes updating the collection problematic. Tools like Harvest provide for the search, retrieval, and maintenance of distributed collections of documents, but the search engines therein typically lag behind the state of the art. Isearch implements full text and Boolean search, term weighting, word left-truncation, fielded search, and phrase searching.
Utilities implement a local caching scheme and automated updating of the searchable index.
Modifications to Isearch treat file names and URLs as instantiations of a text file class, in which local files are opened and read using the usual C file operators, and remote files are retrieved using a network interface. Once the remote file has been retrieved and its contents indexed, the local copy can either be retained in the cache or discarded, with the URL retained as a file pointer. Unlike robots and Web walkers, the input to the enhanced Isearch is an explicit list of file names and URLs, so that only documents of direct interest are included, minimizing bandwidth.