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A web application (or web app) is application software that runs on a web server, unlike computer-based software programs that are run locally on the operating system (OS) of the device. Web applications are accessed by the user through a web browser with an active network connection. These applications are programmed using a client–server modeled structure—the user ("client") is provided services through an off-site server that is hosted by a third-party. Examples of commonly-used web applications include: web-mail, online retail sales, online banking, and online auctions.

History

In 1995, Netscape introduced a client-side scripting language called JavaScript allowing programmers to add some dynamic elements to the user interface that ran on the client side. So instead of sending data to the server in order to generate an entire web page, the embedded scripts of the downloaded page can perform various tasks such as input validation or showing/hiding parts of the page.

In 1999, the "web application" concept was introduced in the Java language in the Servlet Specification version 2.2. . At that time both JavaScript and XML had already been developed, but Ajax had still not yet been coined and the XMLHttpRequest object had only been recently introduced on Internet Explorer 5 as an ActiveX object.

In 2005, the term Ajax was coined, and applications like Gmail started to make their client sides more and more interactive. A web page script is able to contact the server for storing/retrieving data without downloading an entire web page.

Structure

Applications are usually broken into logical chunks called "tiers", where every tier is assigned a role. Traditional applications consist only of 1 tier, which resides on the client machine, but web applications lend themselves to an n-tiered approach by nature. Though many variations are possible, the most common structure is the three-tiered application. 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, CGI, ColdFusion, Dart, JSP/Java, Node.js, PHP, Python or Ruby on Rails) is the middle tier (application logic), and a database is the third tier (storage). 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 it may be beneficial to use an n-tiered approach, where the greatest benefit is breaking the business logic, which resides on the application tier, into a more fine-grained model. Another benefit may be 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. For example, the client data would be accessed by calling a "list_clients()" function instead of making an SQL query directly against the client table on the database. This allows the underlying database to be replaced without making any change to the other tiers.

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. 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. 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.

Business use

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Security breaches on these kinds of applications are a major concern because it can involve both enterprise information and private customer data. Protecting these assets is an important part of any web application and there are some key operational areas that must be included in the development process. This includes processes for authentication, authorization, asset handling, input, and logging and auditing. Building security into the applications from the beginning can be more effective and less disruptive in the long run.

Development

Writing web applications is often simplified by the use of web application framework. These frameworks facilitate rapid application development by allowing a development team to focus on the parts of their application which are unique to their goals without having to resolve common development issues such as user management. Many of the frameworks in use are open-source software.

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 on the framework while another focuses on a specified use case. 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 such as GET after POST.

See also

• Software as a service (SaaS)
• Web 2.0
• Web engineering
• Web services
• Web Sciences
• Web widget
• Single-page application
• Ajax (programming)
• Web development tools
• Browser game
• API economy
• Mobile app
• Progressive web application

References

1. Liam Tung (2020-06-15). "JavaScript creator Eich: My take on 20 years of the world's top programming language". ZDNet.
2. Davidson, James Duncan; Coward, Danny (1999-12-17). Java Servlet Specification ("Specification") Version: 2.2 Final Release. Sun Microsystems. pp. 43–46. Retrieved 2008-07-27.
3. Jay Hoffmann (2019-03-04). "What Does AJAX Even Stand For?". Retrieved 2021-10-18.
4. ^ Petersen, Jeremy (4 September 2008). "Benefits of using the n-tiered approach for web applications".
5. "Top Tips for Secure App Development". Dell.com. Archived from the original on 2012-05-22. Retrieved 2012-06-22.
6. Multiple (wiki). "Web application framework". Docforge. Retrieved 2010-03-06.
7. Multiple (wiki). "Framework". Docforge. Retrieved 2010-03-06.

External links

• HTML5 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
• Template:Curlie
• Web Applications Working Group at the World Wide Web Consortium (W3C)
• PWAs on Web.dev by Google Developers.

• Software architecture
• Web applications
• Web development
• User interface techniques