WWW Programming Model

WWW Model

• The Internet WWW architecture provides a flexible and powerful programming

model.

• Applications and content are presented in standard data formats, and are browsed

by applications known as web browsers.

• The web browser is a network application, i.e., it sends requests for named data

objects to a network server and the network server responds with encoded data

using the standard formats.

The WWW standards specify several mechanisms necessary to build a general-purpose application environment which includes:

• Standard naming model.

– All servers and content on the WWW are named with an Internet-standard Uniform

Resource Locator ( URL ).

• Content typing.

– All content on the WWW is given a specific type, thereby allowing web browsers to

correctly process the content based on its type.

• Standard content formats.

– All web browsers support a set of standard content formats.

– These include (HTML), JavaScript scripting language (ECMAScript, JavaScript), and a large

number of other formats.

• Standard protocols.

– Standard networking protocols allow any web browser to communicate with any web server.

– The most commonly used protocol on the WWW is the HTTP.

– This infrastructure allows users to easily reach a large number of third party applications and

content services.

– It also allows application developers to easily create applications and content services for a

large community of clients.

The WWW protocols define three classes of servers:1. Origin server:

The server on which a given resource (content) resides or is to be created.

2. Proxy:

- An intermediary program that acts as both a server and a client for the purpose of making requests on

behalf of other clients.

- It resides between clients and servers that have no means of direct communication (e.g., across a

firewall).

- Requests are either serviced by a proxy program or passed on with possible translation to other servers.

- A proxy must implement both the client and the server requirements of WWW specifications.

3. Gateway:

- A server which acts as an intermediary for some other server.

- Unlike a proxy, a gateway receives requests as if it were the origin server for the requested resource.

- The requesting client may not be aware that it is communicating with a gateway.

The Internet Model:

The Internet Model:

• Here WWW client request a resource stored on a web server.

• On the Internet standard communication protocols, like HTTP and Transmission Control

Protocol/Internet Protocol (TCP/IP) are used.

• The content available at the web server may be static or dynamic.

• Static content is produced once and not changed or updated very often; for example, a

company presentation.

• Dynamic content is needed when the information provided by the service changes more often;

for example, timetables, news, stock quotes, and account information.

• Technologies such as Active Server Pages (ASP), Common Gateway Interface (CGI), and

Servlets allow content to be generated dynamically.

 

The WAP Model

• The WAP programming model is similar to the WWW programming model.

• Purpose of WAP:

To enable easy, fast delivery of relevant information and services to mobile users.

 

• Type of devices that use WAP:

Handheld digital wireless devices such as mobile phones, pagers, two-way radios, smart phones and

communicators -- from low-end to high-end.

• WAP works with most Wireless networks  such as:

CDPD, CDMA, GSM, PDC, PHS, TDMA, FLEX, ReFLEX, iDEN, TETRA, DECT, DataTAC,

Mobitex.

The WAP Model

• WAP Gateway/Proxy is the entity that

connects the wireless domain with the

Internet.

• The request that is sent from the wireless

client to the WAP Gateway/Proxy uses the

Wireless Session Protocol (WSP).

• A mark-up language – It has been

adapted to develop optimized WAP

applications to save valuable bandwidth in

the wireless network, it can be encoded

into a compact binary format.

How WAP Model Works?

• The user selects an option on their mobile device that has a URL with Wireless Markup

language (WML) content assigned to it.

• The phone sends the URL request via the phone network to a WAP gateway using the binary

encoded WAP protocol.

• The gateway translates this WAP request into a conventional HTTP request for the specified

URL and sends it on to the Internet.

• The appropriate Web server picks up the HTTP request.

• The server processes the request just as it would any other request. If the URL refers to a static

WML file, the server delivers it. If a CGI script is requested, it is processed and the content

returned as usual.

How WAP Model Works?

• The Web server adds the HTTP header to the WML content and returns it to the gateway.

• The WAP gateway compiles the WML into binary form.

• The gateway then sends the WML response back to the phone.

• The phone receives the WML via the WAP protocol.

• The micro-browser processes the WML and displays the content on the screen.

WAP defines a set of standard components that enable communication between mobile terminals and network servers, including:

Standard naming model :

WWW-standard URLs are used to identify WAP content on origin servers. WWW-standard

URLs are used to identify local resources in a device (e.g., call control functions). 

Content typing :

All WAP content is given a specifi c type consistent with WWW typing. This allows WAP

user agents to correctly process the content based on its type.

Standard content formats :

WAP content formats are based on WWW technology and include display markup,

calendar information, electronic business card objects, images, and scripting

language.

 Standard protocols :

– WAP communication protocols enable the communication of browser requests from the mobile

terminal to the network web server.

– The WAP content types and protocols have been optimized for mass market, hand-held

wireless devices.

– WAP utilizes proxy technology to connect between the wireless domain and the WWW.

Hardware and Software Requirement:

• A web server with connection to the Internet

• A WML to develop WAP application

• A WAP simulator to test WAP application

• A WAP gateway

• A WAP phone for final testing.

USAGE

• Corporate Applications:

Sales force automation where sales people use their WAP enabled handsets to get instant,

direct access to the latest pricing, latest news, competitive information any time, anywhere.

• Online Services:

– Banking:

Users can get their current balance, transfer funds between accounts and receive

fax of a mini-statement.

– Electronic Commerce:

Subscribers can use their handset just like their PC to purchase products and

services over the Web.

• Tele services

- Prepaid Services:

With a WAP-enabled phone, prepaid subscribers can see their current balance with the press of a button

And can also recharge their account by entering a credit card or voucher number into the handset.

• Personal Productivity

Email: Using WAP users can keep track of their email right from their handset.

• Others include:

- Interactive Chat

- Auctions

- Games

Disadvantages:

• Small screens: For web phones, there's an incredibly small viewing area; palmtops are barely

better.

• Speed of access: All devices have slow access.

• Limited or fragmented availability: Wireless web access is sporadic in many areas and

entirely unavailable in other areas.

• Price: Many technology limitations are being addressed by higher-end devices and services.

But the entry price for a good wireless web palmtop with decent display, keyboard, and speed

is easily $700 to $900, not including monthly access.

• Lack of user habit: It takes some patience and overcoming the learning curve to get the hang

of it -- connecting, putting in an address, typing. Users just aren't used to the idea and protocol

yet.