Топик: Internet

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.

Alta Vista.

Its(her) address http://altavista.digital.com. This system has appeared in December 1995. She (it) one of largest on volume of indexes from all such retrieval systems both most powerful and floppy rules of construction of searches. Alta Vista understands two different languages of searches rather strongly distinguished from each other. On the first page Alta Vista you see the form for simple search (Simple Search), and the panel of heading at the top of page contains the button Advanced Search, having pressed which, you receive the form for complication of search.

Except for WWW-pages, Alta Vista conducts a separate index for clauses from more than 14000 conferences Usenet (including hierarchy of groups relcom. *).

Search Alta Vista: that Alta Vista worked on group of words, only when they cost(stand) beside, it is necessary to conclude this group in inverted commas. If it is necessary to exclude from result all documents containing a certain word, it is necessary to attribute this word with is familiar “minus”.

The word without any mark works in search precisely the same as also it with is familiar “plus”.

As against Yahoo, by default Alta Vista searches of entry of the whole words. The ordered terms should stand in the document separately, instead of to be a part of other chains of symbols. If you need to find of all entry of a word, even when it is included into structure of other words, use a symbol *. The asterisk can stand only at the end of a word, and prevent giving many (too much) of results, Alta Vista requires(demands), that the word which is coming to an end on *, should consist not less than of 3 letters. Moreover, a symbol * allows to find not any termination (ending) of a word, but only not exceeding length of five symbols and not containing of capital letters or figures.

Results of search Alta Vista, as well as Yahoo, gives out as the list of the links on the documents, but instead of the description of each document near to his(its) heading you will see simply first some lines of his(its) text. If will be found more than 10 documents, Alta Vista will break their list on pages till 10 links on everyone. Alta Vista sorts the links so that on the first place there were “most important” documents with your keywords at definition of a degree of importance taking into account the following factors:

Whether the keywords into heading of the documents enter;

Whether these words in the first several lines of the documents contain;

As far as are close to each other in the text the keywords are found out.

Info seek

Info seek, entered in of operation at the end of 19996 years, is somewhat reminiscent Alta Vista, however volume of the complete texts, surveyed by him,(it,) of the documents yet does not exceed 30 million. Web-pages. The address: http://www.infoseek.com. It is rather powerful system having high speed and idle time in circulation. Opportunities of drawing up of search almost same, as well as in Alta Vista, but not so rich. At almost complete preservation of values of marks "«plus", "«minus" and "«inverted commas", sensitivity to a difference header both lower case letters and opportunity to limit search to fragments Web- of pages, Info seek yet has no ability to define(determine) beside the worth terms (there is no operator NEAR), to limit search by date of updating a source and, main, to truncate terminations(ending) the key terms.

But the given retrieval system contains weight of facultative functions., for example, opportunity concerns to those to define(determine) quantity(amount) of the links in WWW on concrete page, that is to judge, as far as she(it) is popular or, on the contrary, to find out, how many links to external pages contain on the given site, more correctly, how many from them are reflected in index files Ultra seek. Use of special function Image seek allows to find in Internet of the image (figures, photo) on the certain subject. Info seek has also one of the best directories of resources of a Network.

HotBot

By one of powerful search means in World Wide Web can attribute (relate) HotBot, containing the items of information on the complete texts 110 million. Pages. The address: http://www.hotbot.com. HotBot belongs to the newest systems, therefore his (its) profound search gives amazingly ample opportunities for detailed elaboration of search. It is reached (achieved) at the expense of use of the multistage menu offering various variants of drawing up of the search instruction. It is possible to carry out search on presence in the document one or several terms, search on a separate phase, search of the concrete person or links to the certain electronic address. For the greater detailed elaboration of search probably application of conditions SHOULD (can contain), MUST (should necessarily contain), MUST NOT (should not contain) in relation to any concepts. Besides HotBot represents возможность ограничить search by date of creation or last updating of the document, on geographic a rule(situation) of the server. Top of service opportunities is the search of the documents containing certain types of files, for example video. For this purpose it is necessary only to make a mark in special item of the menu of search.

WebCrawler.

It is one more tool of search such as search-bot (search the robot). The address: http: // www.webcrawler.com. The search here is very simple. Enter maximal keywords into a field of search, press Search.

Lycos.

It is the large database that contents of all pages, found by Web.

The address: http://www.lycos.com.

World Wide Web Worm.

You will find this tool of search on http://www.cs.colorado.edu/home/mcbryan/wwww.html. It is one more extensive index of sites Web.

In each concrete case it is expedient to use the tool of search. You should try to carry out(spend) search through one tool and, if you have not received results, to pass to another. But nevertheless what tool to use? First of all it is better to take advantage of the thematic catalogue such as Yahoo, size at them rather small, but the speed is great. If to find the necessary information it was not possible, it speaks that you are interested in a too narrow subject, or badly correspond with your subject the keywords, chosen by you. It does not mean, that the necessary information in WWW is not present - it will be simple to find her(it) more difficultly. For its(her) search to you will be reached to take advantage of more primitive, more automatic and consequently by more universal systems such as Alta Vista.

2.3. Russian retrieval systems

The retrieval systems of global scale concentrate the basic attention on English resources of a Network. The task of search of the information on servers within the limits of the separate countries is carried out with systems of local character specially adapted for features of concrete languages. There are similar search means and in Russia. All of them are united by (with) an opportunity of processing of materials in all Cyrillic codes*. However on capacity and level of offered service the Russian retrieval systems considerably differ from each other.

Rambler, "Апорт" and "Яndex" now concern to leading group systems.

Rambler