Internet

The classification of retrieval systems is more convenient for building all on the basis of on the tax and processing of the information given to the users, - or else how many is automated in them, who types(collects) a database, in which the search is made: the people or computers.

2. Tools of search

Conditionally tools of search are subdivided into search means of a help type (directories) and retrieval systems in the pure state (search engines).

2.1 Thematic catalogues

The search tools of the first type name subject, or thematic catalogues more often. The company owning such catalogue, continuously conducts huge work, investigating, describing, cataloguing and displaying on half-glasses contents of WWW-servers and other network resources scattered worldwide. Result her(it) titanium of efforts is the constantly updated hierarchical catalogue, at the top level the most general(common) categories, such as “business” are assembled, "”science", "”art" etc., and the elements of the lowermost level represent the links to separate WWW-pages and server together with the brief description of their contents.

Guarantees that such catalogue really covers all contents WWW, nobody will give, however possible(probable) not the completeness and selection of materials is with interest expiated there, that for the present not under force to any computer - intelligence of selection.

The subject catalogues give also opportunity of keyword search. However search this occurs not in contents of WWW-servers, and in their brief descriptions stored(kept) in the catalogue.

The subject catalogues Internet can be counted literally on fingers, as their creation and support require(demand) huge expenses. To most known concern Yahoo, WWW Virtual Library, Galaxy and some other.

Yahoo.

Is most popular in the population Internet the catalogue Yahoo. On the first page Yahoo, located to the address http://www.yahoo.com, you receive access to two basic method of work with the catalogue - keyword search and hierarchical tree of sections.

Having begun descent(release) on sections of the catalogue, you will see, that each section contains the precisely same field for input of keywords and button Search, starting search.

Each section can include as transfer included in him(it) and actually links to pages concerning at once all section, with their brief descriptions.

Instead of travel you can at once get in the necessary place of the catalogue Yahoo with the help of search. Having entered one or several keywords divided(shared) by blanks, in a line of search and having pressed the button Search, you receive the list all in Yahoo, that comprises the specified keywords. This list will be divided(shared) into two parts - “categories” and “sites”.

If total of the links returned as a result of search, exceeds 25, the list of the links will be broken on some parts.

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 ”.