Analysis and Testing of Ajax-based Single-page Web Applications

Figure 1.1 The WWW growth. Note: Sites = number of web servers (one host
may have multiple sites by using different domains or port numbers). Taken from
(Zakon, 2006).
party. The Uniform Resource Locator (URL) is a URI, which also specifies
the location of the identified resource and the protocol for accessing
it (Berners-Lee et al., 1994);
• The HyperText Markup Language (HTML), to format data in hypertext
documents. Hypertext refers to text on a computer that makes a dynamic
organization of information through connections (called hyperlinks)
possible;
• The HyperText Transfer Protocol (HTTP), an application-level, stateless
request-response protocol for distributed, hypermedia information systems
(Fielding et al., 1999). It is used for transporting data on the network
between the client (e.g., browser) and server. The protocol supports
eight operations: GET, POST, HEAD, PUT, OPTIONS, DELETE,
TRACE, and CONNECT. In practice, mostly the fist two are used to
GET pages from, and POST user data to, servers.
Using these concepts, a simple but powerful client/server architecture was
developed in which resources could be linked together and easily accessed
through web browsers. In the early nineties, the web was merely composed
of linked simple static hypertext documents. Upon sending a request to the
server, the server would simply locate and retrieve the corresponding web
page on the file-system, and send it back to the client browser. The browser
would then use the new web page to refresh the entire interface. Figure 1.2
shows one of the first web browsers called Mosaic, credited with popularizing
the web because of its user friendly interface.
1.1.2 Dynamically Generated Pages
After the wide adoption of the web, more complex web applications began to
flourish, moving from static pages on the file-system to dynamically assem-
2 1.1. Web Evolution