An application of Web or a Web application is a computer program, which is implemented on a Web server, whereby an interaction with the user is made exclusively by a Webbrowser. For this the computer user (Client) and the server are connected by a network, like Internet or by an Intranet, so that the spatial distance between Client and servers is insignificant.

Function mode

The user starts an application of Web, by entering the URL of the Web server in a Browser and sending thus the first inquiry (HTTP Request). The Web server receives this inquiry and hands it over to the actual application of Web. This generates thereupon the HTML source code of a web page, which is sent by the Web server back to the Browser of the user (HTTP Response). This web page is the graphic user surface of the application of Web.

By clicking one hyper+on the left of on this web page or by filling out and mailing a form starts the user a renewed inquiry to the Web server. Here typically further information becomes, how processes e.g. the inputs transacted in the form (HTTP POST OFFICE) or the parameters of on the left of (HTTP GET), to the Web server conveyed and as input by the application of Web. One calls the processing of such HTTP Requests by the application of Web also Request Cycle.

While an application of Web originally generated only the HTML source code of the web pages, in the meantime also arbitrary other elements, which can be represented in a Browser, are generated. In addition belong above all pictures, pdf documents or Flash animations.

Demarcation

Applications of Web can be distinguished from others, similar technologies well, since the interaction with the user is made by definition exclusively by a Browser.

Rich Internet Application

A Rich Internet Application (RIA) presupposes a higher measure of program logic on the Client, with which for example computations can be accomplished instead of on the server now on the Client by definition. Strict-taken it acts with applications of Web, the Javascript, Java applet, Flash animations, ActiveX Plugins and begin, also around RIAs, if these elements are involved in the interaction with the user.

Web service

With a Web service a Web server makes information available in one structures format, which is meant to the direct announcement not primarily. The use of XML is not sufficient alone for demarcation against an application of Web, since these fall back since the introduction of XHTML also to XML. With a Web service the XML data are however meant for subsequent treatment in any program on the Client. Here even the interaction with a user is not a compelling condition.

Architecture

An application of Web usually runs on the Web server, can be paged out in the professional range also on one or more Application servers however in particular, which are served of or several Web servers with user inquiries. One can differentiate between in principle two architectures:

Condition alone

The application of Web is its own binary program or a script interpreted by its own binary program, which is again started for each inquiry. The return of this program is sent by the Web server as answer to the Browser. Example: Common gateway interface (cgi).

Integrated

The application of Web is part of the Web server or a script interpreted by the Web server. Thus no strange program must be started in the context of a Request Cycles. Examples: PHP, Perl (in each case interpreted by a module of the Web server), Java Servlet or JavaServer Pages

Are to be persisted to applications of Web dependent on it data, these are stored either in one or more files in the file system of the Web server or in an attached data base. User specific data can be stored to small extent also in so-called Cookies by the Browser on the computer of the user, if this permits this.

Regards one applications of Web as multi-animal architecture is realized the presentation layer by the Browser on the Client.

Comparison

Advantages

Applications of Web presuppose a Webbrowser on the computer of the user only, which is fulfilled on the very most computer nowadays. Contrary to conventional Client server applications thus no further installation of software on the computers of the users is necessary. Thus applications of Web achieve a high degree at platform independence.

If the logic of an application of Web must be changed, changes are only in (central) a place, i.e. on the Web server, necessary, which affects maintenance costs favorably.

By, like mobile telephones or PDAs applications of Web find a spreading fast to always far going spreading of Browsern on other terminals beyond the classical software environments.

Disadvantages

An application of Web needs constant TCP/IP a connection between the Client and the server; the connection can be separated theoretically between two Request Cycles and developed again. In addition the range of the connection must be designed for the requirements of the application of Web. This circumstance e.g. excludes applications of Web for a row of employment scenarios, like the mobile off-line use, by definition.

Unfortunately applications of Web have to fight much with the different Browsern, to interpret the HTML different despite existing standards. In addition only an asynchronous processing is necessary by the Request Cycle represented above, which excludes a set of areas of application (e.g. the treatment of diagrams) as application of Web or clearly difficult.

Articles in category "Application of Web"

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