Basic protocols in Internet and search in them
Internet contains vast quantity (amount) of the information; on this in it (him) it is difficult to find that that is necessary if not to know where to search. The place of a presence (finding) (or address) each resource defines (determines) it(him) URL. In URL the type of the protocol indicating on what server contains the access is carried out: on WWW (on which specifies recording: http), Gopher, ftp, telnet, or WAIS, it depends on that what type of the information you will transfer. The network protocol - set of the precisely certain rules: how to request, to make out and to send on a network the given version of the information
Telnet
Millions computers are joined (attached) to a network Internet and many from them have interesting opportunities.
It appears, is quite feasible to reach these computers to look databases, available in them, and programs. The special program telnet allows transforming your computer into the client telnet for a data access and programs in numerous servers telnet. For example researcher regularly can work on several computers, which managers nominate to it (him) a special name and password.
In itself telnet - the communication facility is simple; neither any of the own interface, nor opportunities of search it (he) does not give.
Having contacted the help telnet with the removed machine and having entered in a field of search the entrance name (login) and password (password) you communicate with this machine and programs on further to it(her), and telnet cares only of maintenance of communication(connection) between you.
Certainly, many storehouses of the information, which were originally served by the special programs with access on telnet now it is possible to transfer (translate) on WWW, that not seldom and is done(made). However there were also such which on former give the services only on telnet (especially among the catalogues and information services of libraries).
Standard the link on telnet connection with some site Internet (i.e. URL- the address of this connection) looks so:
telnet: // < the address of the server >
FTP
Practically information is stored (kept) in the computer world as files. On this for itself заре Internet the special means for an exchange of files on a network - network protocol FTP (File Transfer Protocol) has appeared.
The quantity (amount) of files accessible on sites of all world on anonymous FTP is measured in astronomical figures and constantly grows. Besides Word Wide Web allows without any alteration existing FTP of archives, to supply with their descriptions of any degree of detail and convenient hypertext interface.
But how to learn (find out) where to address in searches of the necessary file?
Archie
The search on a name of a file on all anonymous FTP-sites of the world can be carried out with the help of system Archie. She(it) is developed by the several programmers from university Magellan in Canada and carries out indexation of stations FTP, showing files, accessible in everyone station. Archie informs several millions files taking place in more thousand stations FTP, and gives a surprisingly fast way of search of that place, where it is necessary to be directed for reception of a file, interesting for you. The search in a database of the server Archie is made with the help of keywords, which in this case represent simply names of files or fragments of names.
Now Archie is accessible through WWW. It WWW page with the form in which the keywords and options of search are specified.
Though the name of a file almost always has a certain attitude (relation) to his (its) contents, to use Archie for thematic search of the programs does not cost. This system will be useful, if you really know a name of the necessary file or part of a name. On the other hand if you search for the program, which has the standard reduced name, that is some probability that this reduction will be present and at a name of a file, so it is possible to try to find such file with the help Archie. The results of search represent the list of FTP-sites and complete names of files on these sites. The name of a file serves the link to this file, so the click on a name will allow at once receiving a file from the given site. And domes the address of FTP-archive allocated by a large greasy font will transfer you to the initial catalogue of file system on this archive.
Archie the list into the list into the list into the list into the reception.
URL-address indicating FTP-connection, owes, as a minimum to include a word “ftp” as the left part and address of the site in right:
ftp: // < the address of the server >.
WAIS
Almost all information resources Internet give an opportunity of automatic search, but only in one of them - in system WAIS (Wide Area Information Server, global information server) - the keyword search, is the basic method of access to the information.
The system WAIS represents the huge distributed (allocated) database, i.e. the separate parts of this database are located on different net points worldwide. The program - client for work with servers WAIS not only is able to communicate with them under the special protocol, but also stores (keeps) the list of all databases WAIS with their addresses and names, and sometimes and with the brief descriptions. There it is possible to find archives of news, every possible catalogues, directories, collections of scientific clauses and abstracts, indexes and much another. Practically any information, for which the database is the convenient form by performances which is interesting enough to a wide audience, can be submitted in WAIS.
The database WAIS is so great, that idle time of recordings - extremely unpromising way of access to the information. Therefore in WAIS the rather complex (difficult) method of keyword search and phrases is applied. The documents received as a result of search, are sorted by the WAIS-server by quantity (amount) of entry in them of keywords and on, as far as is complete in each of them all set of the ordered keywords is submitted. Such system is capable to give good results, is especial if to break process of search at some stages.
The first stage of search usually is the search special in a database under the name “directory-of-servers”, which contains small on volume of the description (abstracts) of all other bases WAIS. Thus it is better to specify not those keywords, which at the end interest you, and those general(common) concepts concerning your field of knowledge.
Having chosen on the first stage of one or several bases, it is possible to begin search actually of documents - that also it is possible to do (make) in some calls, getting acquainted after each search with results and changing the list of keywords, the necessary document will not be found yet. Besides WAIS has one useful property: if at the next stage of search you have found the document, which contents are especially close that you search, it(he) can be added to the list of the relevant documents. In result at the following stage WAIS will find the documents, not only containing a set of your keywords, but also similar on the dictionary structure on those texts, which you have specified as most suitable.
Though Netscape is capable to work with servers WAIS, for this purpose it (he) should know the address of the special proxy for the protocol WAIS, of which your provider can not appear. The special WAIS-clients working including under Windows, not only convenient for interactive search in databases, but also allows managing services any of the server – intermediary.
URL-address for WAIS looks as:
wais: // < the address of the server > / < the name of base >
Gopher
Each of the considered till now Internet protocols quite could exist in itself: telnet gives access to the programs, FTP - to files, WAIS - to databases. All these systems were created both developed almost independently from each other and put before itself the concrete purpose - to construct the mechanism of access to one certain kind of resources.
However as Internet of dews also became complicated, it (he) pushed the people to an idea, that the information on a nature is uniform and what not too reasonably to divide her (it) on different “kinds of resources” with unlike methods of access. By the end of 80-s' years the idea of a new universal remedy of work with the diverse information was carried in air.
The first system called to embody for life these dreams began Gopher, appeared on light 1991 at the American university of state Minnesota. Fundamental concept incorporated in its (her) basis was structure enclosed each other menu.
Having communicated Gopher- by the client with one of Gopher-servers, you first of all get in the root, main menu of this server. Having oriented in his (its) contents and passing further from one submenu in another, it is possible to engage actually in search of the information. The information in system Gopher is organized strictly hierarchically, “from the general to the particular”. On each step the server sends yours Gopher - client not only contents of the next menu, but also service information on, where there are objects appropriate to items it the menu. The client deduces on the screen only transfer of items, but when you choose one from them, it (he), having verified with the information, available at him (it), or will send on any of Gopher - servers search about distribution of the following of the menu, or will try to establish FTP- or telnet- connection with some site Internet.
Obviously from all information tools Internet Gopher most of all is similar on WWW - both these systems are called to serve the shell with diverse resources. However Gopher is deprived of those rich representational means, which do (make) WWW not only information catalogue, but also new mass media and even by a new genre of art. It is possible to tell, that Gopher is “subset” WWW - that very much simplifies integration itself Gopher as one of kinds of resources in WWW. Practically all that is told about work with Gopher - by the client fairly and for travel on system Gopher with the help of a browser WWW.
URL of one the menu consists of items Gopher - from addresses Gopher- of the server and listed those items of the menu, which will result you in initial item:
gopher: // < the address of the server > / < item of the menu >
WWW
In spite of the fact that per the first years of the existence Gopher has won the large popularity, the need in any became ripe more simple and in too time to maximum universal system, in which communication(connection) between resources would be more free and associative. Such system was developed in 1993 and is named World Wide Web (WWW). System WWW to be under construction on concept of a hypertext, or, is exacter than hypermedia. The hypertext is a text of which component are connected with each other and to other texts with the help of the links. The hypermedia is that that will turn out from a hypertext if to replace in his (its) definition a word “text” on “ any kinds of the information ”: the graphic images, video, sound etc.
World Wide Web “world wide web” means literally. Why she(it) so refers to as. As it is clear from the name, she (it) is global. You not always know in what part of light there is a computer, to which you are connected. You can begin to read page Web in Dallas, then to proceed (pass) in Australia, and all this on one pressing of the button of the mouse. WWW is similar to a web. It is a complex (difficult) information network connected hypermedia by communications (connections). WWW allows not refusing information resources already saved in Internet, other means, accessible with the help, - FTP, telnet and Gopher. It is more than that, the work with these resources through WWW is so convenient, that, say, FTP-clients, former at one time by separate class of the programs, now are used only by few.
And nevertheless main in World Wide Web is not convenience of access to FTP- of archive and Gopher-menu. The majority of servers of system WWW offers the information, which without WWW hardly in general when or would get in a network. Speed of creation and updating, the rich representational opportunities in a combination to ease of access and huge audience have made WWW by new mass media. The start WWW-servers and creation of WWW-pages already has turned of a style to new business - with all that is peculiar to modern business: by a payment for square centimeters of the advertising area.
On the other hand, the fast distribution of system so naturally uniting diverse resources, was promoted not in the last instance by its (her) origin not in the deepest layers of a business concern, and in scientific establishment - European laboratory of physics of particles, which employees did not begin to do (make) of secrets of the development and have not tried at all on it (her) to grow rich.
Fortunately, nature WWW as first of all means of search and organization of the information allows to hope, that this remarkable invention to not turn to the tool of only one commerce and advertising.
The servers and clients WWW communicate among themselves under the special protocol HTTP (Hyper Transfer Protocol, hypertext transfer protocol). URL for WWW looks as:
http: // < the address of the server >
To pass from one page Web to another - an interesting way of research World Wide Web, however you early or late need to find something concrete. But thus it to make it will be not possible. In Internet there are special tools of Web-search.
Tools of search in WWW
Tools of search of the information in Internet constructed on different principles and pursuing the different purpose, exist much. But all unites them that they settle down on the specially allocated network computers with powerful channels of communication (connection), serve every minute huge quantity (amount) of the visitors and require (demand) of the owners of significant expenses on support and updating. Nevertheless, almost all of them respond on searches of the users completely бескорыстно, and the sponsors and advertisers pay for this pleasure. On scales of influence on network community of retrieval systems, undoubtedly, are one of corner stones 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.
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).
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-glass 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 ”.
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.