Web application {{nofootnotes|date=February 2008}} {{mergefrom|Rich Internet application|Talk:Web application#Merger proposal|date=July 2008}} [[Image:Horde-portal.png|thumb|250px|[[Horde (software)|Horde]] [[groupware]] is a typical web application.]] In [[software engineering]], a '''Web application''' is an [[Application software|application]] that is accessed via [[Web browser]] over a network such as the [[Internet]] or an [[intranet]]. It is also a computer software application that is coded in a browser-supported language (such as [[HTML]], [[JavaScript]], [[Java (programming language)|Java]], etc.) and reliant on a common web browser to render the application [[executable]]. Web applications are popular due to the ubiquity of a [[client (computing)|client]], sometimes called a [[thin client]]. The ability to update and maintain Web applications without distributing and installing software on potentially thousands of client computers is a key reason for their popularity. Common Web applications include [[Webmail]], online [[retail sales]], [[online auction]]s, [[wiki]]s, [[Internet forum|discussion boards]], [[Weblog]]s, [[MMORPG]]s and many other functions. ==History== In earlier types of [[client-server]] computing, each application had its own client program which served as its [[user interface]] and had to be separately installed on each user's [[personal computer]]. An upgrade to the server part of the application would typically require an upgrade to the clients installed on each user workstation, adding to the [[technical support|support]] cost and decreasing [[productivity]]. In contrast, Web applications dynamically generate a series of [[Web document]]s in a standard format supported by common browsers such as [[HTML]]/[[XHTML]]. [[Client-side scripting]] in a standard language such as [[JavaScript]] is commonly included to add dynamic elements to the user interface. Generally, each individual Web page is delivered to the client as a static document, but the sequence of pages can provide an interactive experience, as user input is returned through Web [[form]] elements embedded in the page markup. During the session, the Web browser interprets and displays the pages, and acts as the ''universal'' client for any Web application. ==Interface== [[Image:Webconverger.png|thumb|250px|[[Webconverger]] [[operating system]] provides an interface for web applications.]] The Web interface places very few limits on client functionality. Through [[Java (Sun)|Java]], [[JavaScript]], [[DHTML]], [[Adobe Flash|Flash]] and other technologies, application-specific methods such as drawing on the screen, playing audio, and access to the keyboard and mouse are all possible. Many services have worked to combine all of these into a more familiar interface that adopts the appearance of an operating system. General purpose techniques such as [[drag and drop]] are also supported by these technologies. Web developers often use client-side scripting to add functionality, especially to create an interactive experience that does not require page reloading (which many users find disruptive){{Fact|date=April 2008}}. Recently, technologies have been developed to coordinate client-side scripting with server-side technologies such as [[PHP]]. [[Ajax (programming)|Ajax]], a web development technique using a combination of various technologies, is an example of technology which creates a more interactive experience. ==Technical considerations== A significant advantage of building Web applications to support standard browser features is that they should perform as specified regardless of the operating system or OS version installed on a given client. Rather than creating clients for [[Microsoft Windows|MS Windows]], [[Mac OS X]], [[Linux|GNU/Linux]], and other [[operating system]]s, the application can be written once and deployed almost anywhere. However, inconsistent implementations of the [[HyperText Markup Language|HTML]], [[Cascading Style Sheets|CSS]], [[Document Object Model|DOM]] and other browser specifications can cause problems in web application development and support. Additionally, the ability of users to customize many of the display settings of their browser (such as selecting different font sizes, colors, and typefaces, or disabling scripting support) can interfere with consistent implementation of a Web application. Another approach is to use [[Adobe Flash]] or [[Java applet]]s to provide some or all of the user interface. Since most Web browsers include support for these technologies (usually through plug-ins), Flash- or Java-based applications can be implemented with much of the same ease of deployment. Because they allow the programmer greater control over the interface, they bypass many browser-configuration issues, although incompatibilities between Java or Flash implementations on the client can introduce different complications. Because of their architectural similarities to traditional client-server applications, with a somewhat "thick" client, there is some dispute over whether to call systems of this sort "Web applications"; an alternative term is "[[Rich Internet Application]]" (RIA). ==Structure== Though many variations are possible, a Web application is commonly structured as a [[Three-tier (computing)|three-tiered]] application. In its most common form, a Web browser is the first tier, an engine using some dynamic Web content technology (such as [[Active Server Pages|ASP]], [[ASP.NET]], [[Common Gateway Interface|CGI]], [[ColdFusion]], [[Java Servlet|JSP/Java]], [[PHP]],[[embPerl]], [[Python (programming language)|Python]], or [[Ruby on Rails]]) is the middle tier, and a database is the third tier. The Web browser sends requests to the middle tier, which services them by making queries and updates against the database and generates a user interface. But there are some who view a web application as a Two-Tier architecture. ==Business use== An emerging strategy for application software companies is to provide Web access to software previously distributed as local applications. Depending on the type of application, it may require the development of an entirely different browser-based interface, or merely adapting an existing application to use different presentation technology. These programs allow the user to pay a monthly or yearly fee for use of a software application without having to install it on a local hard drive. A company which follows this strategy is known as an [[application service provider]] (ASP), and ASPs are currently receiving much attention in the software industry. ==Writing Web applications== There are many [[Web application framework]]s which facilitate rapid application development by allowing the programmer to define a high-level description of the program. In addition, there is potential for the development of applications on [[Internet operating system]]s, although currently there are not many viable platforms that fit this model. The use of Web application frameworks can often reduce the number of errors in a program, both by making the code more simple, and by allowing one team to concentrate just on the framework. In applications which are exposed to constant [[Hacker (computing)#Hacker: Intruder and criminal|hacking]] attempts on the Internet, security-related problems caused by errors in the program are a big issue. Frameworks may also promote the use of best practices such as [[Post/Redirect/Get|GET after POST]]. ==Web Application Security== The [[Web Application Security Consortium]] (WASC) and [[OWASP]] are projects developed with the intention of documenting how to avoid security problems in Web applications. A [[Web Application Security Scanner]] is specialized software for detecting security problems in web applications. == Applications == [[Image:Firefox2.png|thumb|250px|[[Wikipedia]] [[Application software|application]] running in [[Mozilla Firefox]].]] Browser applications typically include simple office software (word processors, spreadsheets, and presentation tools) and can also include more advanced application such as project management software, [[CAD]] Design Software, and point-of-sale applications. '''Examples''' *Word processor and Spreadsheet: [http://docs.google.com Google Docs & Spreadsheets] *CRM Software: [http://www.salesforce.com/ SalesForce.com] == Benefits == Browser Applications typically require little or no disk space, upgrade automatically with new features, integrate easily into other web procedures, such as email and searching. They also provide cross-platform compatibility (i.e Mac or Windows) because they operate within a web browser window. == Disadvantages == Standards compliance is an issue with any non-typical office document creator, which causes problems when file sharing and collaboration becomes critical. Also, Browser Applications rely on application files accessed on remote servers through the internet. Therefore, when connection is interrupted, the application is no longer usable. [[Google Gears]] is a beta platform to combat this issue and improve the usability of Browser Applications. ==See also== {| |- valign=top | width=50% | *[[AJAX]] *[[Adobe Flex]] *[[Active Server Pages|Active Server Pages (ASP)]] *[[Application service provider|Application service provider (ASP)]] *[[Alpha Five]] *[[ASP.NET]] *[[Cascading Style Sheets|Cascading Style Sheets (CSS)]] *[[CNR_(software)#Web_Software|CNR]] *[[ColdFusion]] *[[Content management framework]] *[[Dynamic HTML|Dynamic HTML (DHTML)]] *[[FinSock]] *[[Hypertext Markup Language|Hypertext Markup Language (HTML)]] *[[Web document|Dynamic web document]] *[[JavaScript]] *[[JavaServer Pages|JavaServer Pages (JSP)]] *[[Ruby on Rails]] | width=50% | *[[Django (web framework)]] *[[Perl]] *[[PHP]] *[[Python (programming language)|Python]] *[[Rich Internet application]] *[[Software development]] *[[Web 2.0]] *[[Web 3.0]] *[[Software as a service|Software as a service (SaaS)]] *[[Web application framework]] *[[iMacros|Web application macro language]] *[[Web service]]s *[[List of web application frameworks]] *[[World Wide Web Consortium]] (Web standards) *[[Webconverger]] *[[Web based presentation tools]] | |} ==References== {{reflist}} ==External links== *[http://www.joelonsoftware.com/articles/APIWar.html How Microsoft lost the API war] — A discussion on how web applications are replacing Windows applications *[http://www.whatwg.org/specs/web-apps/current-work/ Web Applications 1.0] is the ongoing work of documenting how Web applications will work. *[http://www.paulgraham.com/road.html The Other Road Ahead] — An article arguing that the future lies on the server, not rich interfaces on the client *[http://dmoz.org/Computers/Internet/On_the_Web/Web_Applications/ Web Applications] in the [[Open Directory Project]] *[http://msdn.microsoft.com/webclientfactory Web Client Software Factory] — A discussion on how to create composite web and page flow applications on the Microsoft platform. [[Category:World Wide Web]] [[Category:Software architecture]] [[Category:Web applications| ]] [[Category:Web development]] [[ar:تطبيق ويب]] [[ca:Aplicació Web]] [[cs:Webová aplikace]] [[de:Webanwendung]] [[el:Διαδικτυακή εφαρμογή]] [[es:Aplicación web]] [[fr:Application web]] [[ko:웹 애플리케이션]] [[id:Aplikasi web]] [[it:Applicazione Web]] [[nl:Webapplicatie]] [[ja:ウェブアプリケーション]] [[pl:Aplikacja webowa]] [[pt:Aplicação Web]] [[ru:Веб-приложение]] [[sk:Webová aplikácia]] [[fi:Web-sovellus]] [[th:เว็บแอปพลิเคชัน]] [[vi:Ứng dụng web]]