Page 150 - DLIS408_INFORMATION_TECHNOLOGY-APPLICATIONSL SCIENCES

Unit 13: Internet Based Resources and Service Browsers

the most common structure is the three-tiered application. In its most common form, the three Notes
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, ASP.NET,
CGI, ColdFusion, JSP/Java, PHP, Perl, Python, Ruby on Rails or Struts2) 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 a 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 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

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.

Task Explain your own idea how web application is useful in business.
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. 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 such as GET after POST.

Applications
Examples of browser applications are simple office software (word processors, online spreadsheets,
and presentation tools), but can also include more advanced applications such as project
management, computer-aided design, video editing and point-of-sale.

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