Datasheet

Chapter 1: Web 2.0, Python, and Frameworks

What changed the landscape forever was embedding a capability in the browser that enabled it to make

an asynchronous call to the server for rendering the web page, and the supporting JavaScript capability

to accept the returned data and update a portion of the page (a

<DIV/> or <SPAN/> element of the page)

without refreshing the entire page (an idea that Microsoft Internet Explorer 5 initially advanced). This

was nothing short of revolutionary and morphed quickly into a realization by developers that the

browser could now host applications that mimicked and in some aspects (scalability, robustness, accessi-

bility, and collaboration) improved on the older RCP applications’ capabilities.

Thus, the term Rich Internet Application ( RIA ) was born, ushering in the Web 2.0 era of tools and sites

based on the simple idea that the Internet was becoming a hosting environment, not just for static pages

and forms, but also for applications that once were restricted to the desktop.

Applications for such tasks as word processing, photo image manipulation, personal information

management — which had been a stronghold for a tiny group of vendors, and were exorbitantly priced

with restrictive usage covenants (the infamous and seldom comprehensible end user license agreement or

EULA ) — were suddenly left in the dust by browser-based versions that were not only free but con-

sumed no private disk space. All because Web 2.0 applications are designed according to a ubiquitous

standard (MVC) and use an asynchronous HTTP request with data returned in XML or Javascript Object

Notation ( JSON ). The request-and-return path is called an XMLHttpRequest or XHR , and the technique

works in all modern browsers.

1 Enter URL

5 Forward user to a new HTML page

6 Request newURL -- Submit form/Select

Button

10 Display new complete HTML page

TIME

2 Make synchronous HTTP request

7 Make synchronous HTTP request

9 Return HTTP response

4 Return HTTP response

3 Retrieve file to

satisfy request

8 Look up URL

WEB 1.0 Process-Example Interaction

User

Web Browser Web Server

KEY:

Interacting with page 1

Interacting with page 2

Waiting

Figure 1-1