In system software, a web application is an application Application software, also known as applications or apps, is computer software designed to help the user to perform singular or multiple related specific tasks. Examples include Enterprise software, Accounting software, Office suites, Graphics software and media players that is accessed over a network such as the Internet The Internet is a global system of interconnected computer networks that use the standard Internet Protocol Suite to serve billions of users worldwide. It is a network of networks that consists of millions of private, public, academic, business, and government networks of local to global scope that are linked by a broad array of electronic and or an intranet An intranet is a private computer network that uses Internet Protocol technologies to securely share any part of an organization's information or network operating system within that organization. The term is used in contrast to internet, a network between organizations, and instead refers to a network within an organization. Sometimes the term. The term may also mean a computer software application that is hosted in a browser-controlled environment (e.g. a Java applet A Java applet is an applet delivered to the users in the form of Java bytecode. Java applets can run in a Web browser using a Java Virtual Machine , or in Sun's AppletViewer, a stand-alone tool for testing applets. Java applets were introduced in the first version of the Java language in 1995. Java applets are usually written in the Java)^{[citation needed]} or coded in a browser-supported language (such as JavaScript JavaScript is an implementation of the ECMAScript language standard and is typically used to enable programmatic access to computational objects within a host environment. It can be characterized as a prototype-based object-oriented scripting language that is dynamic, weakly typed and has first-class functions. It is also considered a functional, combined with a browser-rendered markup language A markup language is a modern system for annotating a text in a way that is syntactically distinguishable from that text. The idea and terminology evolved from the "marking up" of manuscripts, i.e. the revision instructions by editors, traditionally written with a blue pencil on authors' manuscripts. Examples are typesetting instructions like HTML HTML, which stands for HyperText Markup Language, is the predominant markup language for web pages. It provides a means to create structured documents by denoting structural semantics for text such as headings, paragraphs, lists, links, quotes and other items. It allows images and objects to be embedded and can be used to create interactive forms) and reliant on a common web browser to render the application executable In computing, an executable file causes a computer "to perform indicated tasks according to encoded instructions," as opposed to a data file that must be parsed by a program to be meaningful. These instructions are traditionally machine code instructions for a physical CPU. However, in a more general sense, a file containing instructions.

Web applications are popular due to the ubiquity of web browsers, and the convenience of using a web browser as a client A client is an application or system that accesses a remote service on another computer system, known as a server, by way of a network. The term was first applied to devices that were not capable of running their own stand-alone programs, but could interact with remote computers via a network. These dumb terminals were clients of the time-sharing, sometimes called a thin client A thin client is a computer or a computer program which depends heavily on some other computer (its server) to fulfill its traditional computational roles. This stands in contrast to the traditional fat client, a computer designed to take on these roles by itself. The exact roles assumed by the server may vary, from providing data persistence (for. 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, as is the inherent support for cross-platform compatibility. Common web applications include webmail Webmail is an email service intended to be primarily accessed via a web browser, as opposed to through a desktop email client. Some webmail providers use dedicated websites to providing email services, including Gmail, Yahoo! Mail, Hotmail, and AOL Mail; but there are many internet service providers which provide webmail services as part of their, online retail sales Retailing consists of the sale of goods or merchandise from a very fixed location, such as a department store, boutique or kiosk, or by mail, in small or individual lots for direct consumption by the purchaser. Retailing may include subordinated services, such as delivery. Purchasers may be individuals or businesses. In commerce, a "retailer&, online auctions The online auction business model is one in which participants bid for products and services over the Internet. The functionality of buying and selling in an auction format is made possible through auction software which regulates the various processes involved, wikis Wikis may exist to serve a specific purpose, and in such cases, users use their editorial rights to remove material that is considered "off topic." Such is the case of the collaborative encyclopedia Wikipedia. In contrast, open purpose wikis accept content without firm rules as to how the content should be organized and many other functions.

History

In earlier type of client–server computing, each application had its own client program which served as its user interface In the industrial design field of human-machine interaction, the user interface is where interaction between humans and machines occurs. The goal of interaction between a human and a machine at the user interface is effective operation and control of the machine, and feedback from the machine which aids the operator in making operational decisions and had to be separately installed on each user's personal computer A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end user, with no intervening computer operator. This is in contrast to the batch processing or time-sharing models which allowed large expensive mainframe. 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 support Technical support is a range of services providing assistance with technology products such as mobile phones, televisions, computers, or other electronic or mechanical goods. In general, technical support services attempt to help the user solve specific problems with a product—rather than providing training, customization, or other support cost and decreasing productivity Productivity is a measure of output from a production process, per unit of input. For example, labor productivity is typically measured as a ratio of output per labor-hour, an input. Productivity may be conceived of as a metric of the technical or engineering efficiency of production. As such, the emphasis is on quantitative metrics of input, and.

In contrast, web applications use web documents A PDF document requested from SFTP or SMTP protocols, for example, is a web document, but not a web page written in a standard format such as HTML HTML, which stands for HyperText Markup Language, is the predominant markup language for web pages. It provides a means to create structured documents by denoting structural semantics for text such as headings, paragraphs, lists, links, quotes and other items. It allows images and objects to be embedded and can be used to create interactive forms (and more recently XHTML XHTML is a family of XML markup languages that mirror or extend versions of the widely used Hypertext Markup Language (HTML), the language in which web pages are written), which are supported by a variety of web browsers.

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 A webform on a web page allows a user to enter data that is sent to a server for processing. Webforms resemble paper forms because internet users fill out the forms using checkboxes, radio buttons, or text fields. For example, webforms can be used to enter shipping or credit card data to order a product or can be used to retrieve data 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.

In 1995, Netscape introduced a client-side scripting Client-side scripting generally refers to the class of computer programs on the web that are executed client-side, by the user's web browser, instead of server-side . This type of computer programming is an important part of the Dynamic HTML (DHTML) concept, enabling web pages to be scripted; that is, to have different and changing content language called JavaScript JavaScript is an implementation of the ECMAScript language standard and is typically used to enable programmatic access to computational objects within a host environment. It can be characterized as a prototype-based object-oriented scripting language that is dynamic, weakly typed and has first-class functions. It is also considered a functional, which allowed programmers to add some dynamic elements to the user interface that ran on the client side. Until then, all the data had to be sent to the server for processing, and the results were delivered through static HTML pages sent back to the client.

In 1996, Macromedia introduced Flash Adobe Flash is a multimedia platform used to add animation, video, and interactivity to Web pages. Flash is frequently used for advertisements and games. More recently, it has been positioned as a tool for "Rich Internet Applications" ("RIAs"), a vector animation Vector graphics is the use of geometrical primitives such as points, lines, curves, and shapes or polygon, which are all based on mathematical equations, to represent images in computer graphics player that could be added to browsers as a plug-in In computing, a plug-in is a small software computer program that extends the capabilities of a larger program. Plugins are commonly used in web browsers to enable them to play sounds and video clips, or automatically decompressing files. Add-on is often considered the general term comprising plug-ins, extensions, and themes as subcategories to embed animations on the web pages. It allowed the use of a scripting language to program interactions on the client side with no need to communicate with the server.

In 1999, the "web application" concept was introduced in the Java language in the Servlet Specification version 2.2. [2.1?]. ^[1][2] At that time both JavaScript JavaScript is an implementation of the ECMAScript language standard and is typically used to enable programmatic access to computational objects within a host environment. It can be characterized as a prototype-based object-oriented scripting language that is dynamic, weakly typed and has first-class functions. It is also considered a functional and XML XML is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards had already been developed, but Ajax Ajax is a group of interrelated web development techniques used on the client-side to create interactive web applications. With Ajax, web applications can retrieve data from the server asynchronously in the background without interfering with the display and behavior of the existing page. The use of Ajax techniques has led to an increase in had still not yet been coined and the XMLHttpRequest XMLHttpRequest is an API available in web browser scripting languages such as JavaScript. It is used to send HTTP or HTTPS requests directly to a web server and load the server response data directly back into the script. The data might be received from the server as XML text or as plain text. Data from the response can be used directly to alter object had only been recently introduced on Internet Explorer 5 as an ActiveX object. ^[3]

In 2005, the term Ajax Ajax is a group of interrelated web development techniques used on the client-side to create interactive web applications. With Ajax, web applications can retrieve data from the server asynchronously in the background without interfering with the display and behavior of the existing page. The use of Ajax techniques has led to an increase in was coined, and applications like Gmail Gmail is a free, advertising-supported webmail, POP3, and IMAP service provided by Google. Gmail was launched as an invitation-only beta release on April 1, 2004 and it became available to the general public on February 7, 2007, though still in beta status at that time. As of December 2009[update], it has 176 million users monthly. The service was started to make their client sides more and more interactive.

Interface

The web interface places very few limits on client functionality. Through Java Java refers to a number of proprietary computer software products and specifications from Sun Microsystems that together provide a system for developing application software and deploying it in a cross-platform environment. Java is used in a wide variety of computing platforms from embedded devices and mobile phones on the low end, to enterprise, JavaScript JavaScript is an implementation of the ECMAScript language standard and is typically used to enable programmatic access to computational objects within a host environment. It can be characterized as a prototype-based object-oriented scripting language that is dynamic, weakly typed and has first-class functions. It is also considered a functional, DHTML Dynamic HTML, or DHTML, is an umbrella term for a collection of technologies used together to create interactive and animated web sites by using a combination of a static markup language , a client-side scripting language (such as JavaScript), a presentation definition language (such as CSS), and the Document Object Model, Flash Adobe Flash is a multimedia platform used to add animation, video, and interactivity to Web pages. Flash is frequently used for advertisements and games. More recently, it has been positioned as a tool for "Rich Internet Applications" ("RIAs") 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 In computer graphical user interfaces, drag-and-drop is the action of clicking on a virtual object and dragging it to a different location or onto another virtual object. In general, it can be used to invoke many kinds of actions, or create various types of associations between two abstract objects 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. Recently, technologies have been developed to coordinate client-side scripting with server-side technologies such as PHP PHP: Hypertext Preprocessor is a widely used, general-purpose scripting language that was originally designed for web development to produce dynamic web pages. For this purpose, PHP code is embedded into the HTML source document and interpreted by a web server with a PHP processor module, which generates the web page document. As a general-purpose. Ajax Ajax is a group of interrelated web development techniques used on the client-side to create interactive web applications. With Ajax, web applications can retrieve data from the server asynchronously in the background without interfering with the display and behavior of the existing page. The use of Ajax techniques has led to an increase in, a web development technique using a combination of various technologies, is an example of technology which creates a more interactive experience.

Structure

Applications are usually broken into logical chunks called "tiers", where every tier is assigned a role.^[4] Traditional applications consist only of 1 tier, which resides on the client machine, but web applications lend themselves to a n-tiered approach by nature.^[4] Though many variations are possible, the most common structure is the three-tiered In software engineering, multi-tier architecture is a client-server architecture in which the presentation, the application processing, and the data management are logically separate processes. For example, an application that uses middleware to service data requests between a user and a database employs multi-tier architecture. The most application.^[4] In its most common form, the three tiers are called presentation, application and storage, in this order. A web browser is the first tier (presentation), an engine using some dynamic Web content technology (such as ASP Active Server Pages , also known as Classic ASP or ASP Classic, was Microsoft's first server-side script engine for dynamically-generated web pages. Initially released as an add-on to Internet Information Services (IIS) via the Windows NT 4.0 Option Pack, it was subsequently included as a free component of Windows Server (since the initial release, ASP.NET ASP.NET is a web application framework developed and marketed by Microsoft to allow programmers to build dynamic web sites, web applications and web services. It was first released in January 2002 with version 1.0 of the .NET Framework, and is the successor to Microsoft's Active Server Pages technology. ASP.NET is built on the Common Language, CGI The Common Gateway Interface is a standard protocol that defines how webserver software can delegate the generation of webpages to a console application. Such applications are known as CGI scripts; they can be written in any programming language, although scripting languages are often used, ColdFusion ColdFusion is a commercial rapid application development platform invented by Jeremy and JJ Allaire in 1995. Originally designed to make it easier to connect simple HTML pages to a database, by version 2 it had become a full platform that included an IDE in addition to a full Scripting Language. Current versions of ColdFusion, sold by Adobe, JSP/Java Servlets are Java programming language objects that dynamically process requests and construct responses. The Java Servlet API allows a software developer to add dynamic content to a Web server using the Java platform. The generated content is commonly HTML, but may be other data such as XML. Servlets are the Java counterpart to non-Java dynamic, PHP PHP: Hypertext Preprocessor is a widely used, general-purpose scripting language that was originally designed for web development to produce dynamic web pages. For this purpose, PHP code is embedded into the HTML source document and interpreted by a web server with a PHP processor module, which generates the web page document. As a general-purpose, Perl Perl is a high-level, general-purpose, interpreted, dynamic programming language. Perl was originally developed by Larry Wall in 1987 as a general-purpose Unix scripting language to make report processing easier. Since then, it has undergone many changes and revisions and become widely popular amongst programmers. Larry Wall continues to oversee, Python, Ruby on Rails or Struts2) is the middle tier (application logic), and a database is the third tier (storage).^[4] 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.

For more complex applications, a 3-tier solution may fall short, and you may need a n-tiered approach, where the greatest benefit is breaking the business logic, which resides on the application tier, into a more fine-grained model.^[4] Or adding an integration tier that separates the data tier from the rest of tiers by providing an easy-to-use interface to access the data.^[4] For example, you would access the client data by calling a "list_clients()" function instead of making a SQL query directly against the client table on the database. That allows you to replace the underlying database without changing the other tiers.^[4]

There are some who view a web application as a two-tier architecture. This can be a "smart" client that performs all the work and queries a "dumb" server, or a "dumb" client that relies on a "smart" server. ^[4] The client would handle the presentation tier, the server would have the database (storage tier), and the business logic (application tier) would be on one of them or on both. ^[4] While this increases the scalability of the applications and separates the display and the database, it still doesn't allow for true specialization of layers, so most applications will outgrow this model.^[4]

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 frameworks which facilitate rapid application development by allowing the programmer to define a high-level description of the program.^[5] In addition, there is potential for the development of applications on Internet operating systems, 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 simpler, and by allowing one team to concentrate just on the framework. In applications which are exposed to constant hacking attempts on the Internet, security-related problems can be caused by errors in the program. Frameworks can also promote the use of best practices^[6] such as GET after POST.

Applications

Browser applications typically include simple office software (word processors, online spreadsheets, and presentation tools), with Google Docs being the most notable example, and can also include more advanced applications such as project management, computer-aided design, video editing and point-of-sale.

Benefits

Browser applications typically require little or no disk space on the client, upgrade automatically with new features, integrate easily into other server-side web procedures, such as email and searching. They also provide cross-platform compatibility in most cases (i.e., Windows, Mac, Linux, etc.) because they operate within a web browser window.

Drawbacks

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 platform to ameliorate this issue and improve the usability of browser applications, its use is being superseded by the introduction of HTML5 API's such as Web Workers and DOM storage. Since many web applications are not open source, there is also a loss of flexibility, not allowing customizations of software, preventing users from running apps offline (in many cases), and making users dependent on third-party servers.

See also

• Software as a service (SaaS)
• Web 2.0
• Web services

References

1. ^ Alex Chaffee (2000-08-17). "What is a web application (or "webapp")?". http://www.jguru.com/faq/view.jsp?EID=129328. Retrieved 2008-07-27.
2. ^ James Duncan Davidson, Danny Coward (1999-12-17). Java Servlet Specification ("Specification") Version: 2.2 Final Release. Sun Microsystems. pp. 43–46. http://java.sun.com/products/servlet/download.html. Retrieved 2008-07-27.
3. ^ "Dynamic HTML and XML: The XMLHttpRequest Object". Apple Inc. http://developer.apple.com/internet/webcontent/xmlhttpreq.html. Retrieved 2008-06-25.
4. ^ ^{a b c d e f g h i j} Jeremy Petersen. "Benefits of using the n-tiered approach for web applications". http://www.adobe.com/devnet/coldfusion/articles/ntier.html.
5. ^ Multiple (wiki). "Web application framework". Docforge. http://docforge.com/wiki/Web_application_framework. Retrieved 2010-03-06.
6. ^ Multiple (wiki). "Framework". Docforge. http://docforge.com/wiki/Framework. Retrieved 2010-03-06.

External links

• HTML 5 Draft recommendation, changes to HTML and related APIs to ease authoring of web-based applications.
• The Other Road Ahead — An article arguing that the future lies on the server, not rich interfaces on the client
• Web Applications at the Open Directory Project

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