The important factor, directly business of the modern organization, the architecture of corporate information system is influencing.

The architecture of Intranet systems became natural end of the next coil of a information evolution spiral of systems - from systems with the centralized architecture through systems the client-server in traditional understanding to Intranet.

Let's address to mainframes in which in a classical kind there was make an idea of centralization. All computing resources have been concentrated in a uniform complex, huge data files in the same place were stored and processed. Access to these huge systems was carried out by means of the working terminals which are practically not having own computing capacity. Advantages of the centralized architecture are obvious are a simplicity of administration, protection of the information, etc.

Among set of characteristic features of mainframes architecture we shall especially note use as the basic means of access to the information of alphanumeric terminals. The decision looked natural, logical and justified - if access to information system the technical service brought cables to this place somewhere was required and established the terminal which there and then started to work and the user got access to the mainframe. If the terminal broke, the technical service replaced it, and the user continued the work. Generally speaking, the terminal is similar to home appliances - to a washing machine, a refrigerator or an iron - to the simple device, which all time functions, and in case of breakage is exposed to repair or replacement.

Let's pay attention: as the terminal - the device idle time, was not required any special actions on adjustment and the software configuration in a kind of its absence. Terminals operated from the mainframe, that is on-line. The user should not hammer in a head data about the device of terminals - was the nobility as it to include and on what buttons enough to press, to start the program and to work with it. All terminals were same - hence, was guaranteed, that the program started on the mainframe, will work (that is to display the information and to accept input of the user) on all of them absolutely equally. That is, devices on workplaces of users behaved predictedly and could be at any moment replaced.

All this was simply magnificent from the point of view of the companies management where such technology was used. Expenses for service of terminals and communication lines, certainly, were, but it were predicted and predicted expenses for performance of the limited set of cleanly technical actions with absolute result.

But here there was a revolution - there were personal computers. Began possible to have computing and information resources on own workplace and to operate them on own understanding. There was the window graphic interface non-comparable by the opportunities with limited repertoir former alphanumeric or even of graphic terminals. There were new means of input ("mouse" and other manipulators), the interface with the user has become complicated, became the rich and various, sated color, a sound and animation. People have felt taste to work with beautiful and graceful means.

But not this main thing. Have appeared idea of carry of a system part for performance on a personal computer, it is direct on a workplace - really why to not charge to a personal computer to carry out that part of the program which is responsible for the interface with the user (and can be, and that part of the program which realizes applied logic), and functions of data processing to leave on the central computer? Thus, the system became distributed - its one part was carried out on the central computer, another - on personal which has been incorporated in a network with the central server. There was exclusively convenient and natural paradigm the client-server - interaction model of computers and programs in a network. High rates means of applications development in architecture the client-server with which now we use for realization of information systems began to develop.

Intranet architecture is something to averages between mainframes and widely widespread client-server architecture. In Intranet a client part of system is the Internet-browser which, by virtue of the limited opportunities, cannot be the high-grade client application. At least, in the accepted concept of client-server architecture. Therefore in architecture intranet the client refers to "weak" (thin client). In most cases use of a browser is not enough than by opportunities differs from application of the terminal with the (enough powerful) system of commands.

Weakness of the client forces to place logic of the application on a server; actually, for realization not only system of submission of the information (or an advertising hypertext server) it is required to finish essentially functioning of a standard Web-server, transforming it in application server. This server also is heart of all Intranet-architecture.