Magellan

But not seldom happens so, that the list, given out by the machine, is very great and to see (overlook) it (him) simply not really. An output (exit) from this situation can become stricter selection of the information brought in the catalogue. One of most known such systems - catalogue Magellan to the address: http: // www.mckinley.com

This database contains the items of information on 80 thousand WWW-pages - that very much not much in comparison with those in millions, which exist in a network. However if Yahoo as the description of a resource uses one - two lines of the text, the employees of system Magellan on some of pages brought in their database, write the small reviews, and also estimate quality of these information resources on a five-mark scale. Till past bases of the reviews, Magellan owns as an own automatic index, for search in which it is necessary to throw the switch under a field of input in a rule (situation) entire database.

As a rule search represents one or several keywords divided (shared) by blanks.

Point

The service, similar by the principles, of firm Point (http: // www.pointcom.com) in general basic emphasis does (makes) not on search, and on work with the thematic catalogue.

The service Point is known in a network for that its (her) employees are constantly engaged оцениванием of network resources and conduct the lists of those sites, which they consider (count) belong to “ to the best five percents(interests) WWW ”.

Firm Point conducts a shared database all “of five-percentage WWW-pages, where about everyone it is possible to read the detailed license.

Virtual Library

The most old subject catalogue WWW is the catalogue Virtual Library:

http: // www.w3.org/hypertext/DataSources/bySubj ect/Overview.html

This system full enough covers a scientific layer WWW - servers of universities, laboratories and educational institutions.

Russia-On-Line Subject Guide

For the users in our country the certain interest can represent the thematic catalogue Russia-On-Line Subject Guide, located to the address http://www.online.ru/rmain. This catalogue contains rather motley assembly of the links on foreign sources plus the thematic review of the Russian and Russian resources WWW.

Automatic indexes

It is possible to approach to a problem of search of the information in Internet and on the other hand. There are programs in which have loaded some thousand well-known URL-addresses. Being is started on the computer with access to WWW, this program begins automatically to download from a network the documents on it URL, and from each new document she(it) takes all links, contained in it,(him,) and adds them in the base of addresses. As at the end all WWW the documents are connected among themselves, early or late such program will bypass all Internet.

Certainly, the program can not understand as or classify that she(it) sees in a network. The programs of such type refer to as robots. They are limited to the tax of the statistical information and construction indexes in the texts of the documents. The database, collected by the robot, - index - stores (keeps) in it, simply speaking, item of information on that in what WWW-documents to contain those or other words.

Such the automatically collected index also underlies retrieval systems of the second sort, which frequently and name - automatic indexes.

The automatic index consists of three parts: the program - robot collected by this robot of a database and the interface for search in this base, with which the user works. All these components quite can function without intervention of the man.

As any classification of materials in such systems are absent, it is necessary to resort to them only then, when you precisely know keywords concerning that it is necessary, - we shall tell, a surname of the man or it is enough some of rare terms from the appropriate area. If to set search on the a little widespread words, you will have not enough life to bypass all URL-addresses, received as a result of search, - for example, the index of system Alta Vista contains of 11 billions words taken from 30 millions of WWW-pages.

An automatic index of WWW-pages exists much: WebCrawler, Lycos, Excite, Inktomi, Open Text and others. Some of them (for example, Lycos) represent more or less successful synthesis of the subject catalogue and automatic index.