Page 233 - DCAP312_WEB_TECHNOLOGIES_II

Unit 11: Web Services in Visual Studio .NET

Web applications are, therefore, computer programs allowing website visitors to submit and Notes
retrieve data to/from a database over the Internet using their preferred web browser. The data
is then presented to the user within their browser as information is generated dynamically (in
a specific format, e.g. in HTML using CSS) by the web application through a web server.
For the more technically oriented, Web applications query the content server (essentially a content
repository database) and dynamically generate web documents to serve to the client (people
surfing the website). The documents are generated in a standard format to allow support by
all browsers (e.g., HTML or XHTML). JavaScript is one form of client side script that permits
dynamic elements on each page (e.g., an image changes once the user hovers over it with a
mouse). The web browser is key - it interprets and runs all scripts etc. while displaying the
requested pages and content.

Another significant advantage of building and maintaining web applications is that they perform
their function irrespective of the operating system and browsers running client side. Web
applications are quickly deployed anywhere at no cost and without any installation requirements
(almost) at the user’s end.

As the number of businesses embracing the benefits of doing business over the web increases,
so will the use of web applications and other related technologies continue to grow. Moreover,
since the increasing adoption of intranets and extranets, web applications become greatly
entrenched in any organization’s communication infrastructures, further broadening their scope
and possibility of technological complexity and prowess.
Web applications may either be purchased off-the-shelf or created in-house.

11.2.2 How do Web Applications Work?
The Figure 11.2 details the three-layered web function model. The first layer is usually a web
browser or the user interface; the second layer is the active content production technology tool
such as Java servlets (JSP) or Active Server Pages (ASP), and the third layer is the database
containing content (e.g., news) and customer data (e.g., usernames and passwords, social
sanctuary information and credit card details).

Figure 11.2: Three-layered Web Application Model

Server Side Systems
Client Side Browser & PC
Server Operating System,
HTTP Requests Web Server and
to Web Server Scripting Engines to manage
requests and responses
Internet
Responses from Web Server
(HTML, CSS Data, JavaScript, Web
images, Flash Content) Application
Company Website Visitor Server
Database Servers

Database Engine e.g. SQL
Server, Oracle

The Figure 11.3 shows how the initial demand is triggered by the user through the browser in
excess of the Internet to the web function server. The web application accesses the databases
servers to perform the requested mission updating and retrieving the in order lying within the
database. The web application then presents the information to the user through the browser.

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