Communications - February 2009

Web gadget built entirely from Web components—htmL, Css, and Javascript—displays a greeting and photograph both customizable by the user; the photograph is accessed via a uRL.

<?xml version=” 1.0” encoding=”UTF- 8” ?> <Module>

<Content type=”html”><![CDATA[

// Get userprefs var prefs = new gadgets.Prefs(); function greet () {

// Get current time var today = new Date(); var time = today.getTime(); var html = “”;

// Display appropriate greeting html += ...

// Display photo if asked to if ( prefs.getBool(“photo”) == true) { html += ...

} element.innerHTML = html;

}

... gadgets.util.registerOnLoadHandler(greet);

</script>

]]>

</Content>

</Module>

Restful Web aPIs from major Web applications laid the software foundations for Web 2.0.

service

amazon

Google

eBay

Yahoo!

Resource

Xforms Book

Search Hubbell+labrador

aSTeR
Browse autos

ample, weather forecasts were available on Web 1.0, but XML HTTP Request and the ability to asynchronously refresh the content displayed in a Web page through JavaScript callbacks enabled Web sites to integrate weather forecasts into the context of user tasks (such as travel reservations). In addition to being built from Web technologies, a travel site that integrates a variety of information sources in order to deliver a complete task-oriented interface uses the same Web technologies when constructing its constituent components. Note that Web 2.0 is a result of applying Web technologies to the Web. Described differently, Web 2.0 is a conse-

quence of Web(Web()); or writing W for the function Web, a more apt notation for Web 2.0 would be W .

2

Web as Platform

The notion of the Web as a new platform emerged in the late 1990s with the advent of sites providing a range of end-user services exclusively on the Web. Note that none of them had a parallel in the world of shrink-wrap software that had preceded the Web:

Portal. Yahoo! Web directory;

Shopping. Amazon online store;

Auction. eBay auction site; and Search. Google search engine.

In addition to lacking a pre-Web

equivalent, each of these services lived on the Web and, more important, exposed the services as simple URLs, an idea later known as REpresentational State Transfer, or (REST) ful, Web APIs. ¹⁶^{, 17} All such services not only built themselves on the Web, they became an integral part of the Web in the sense that every Google search, auction item on eBay, and item for sale on Amazon were URL addressable (see the table here).

URL addressability is an essential feature of being on the Web. The URL addressability of the new services laid the foundation for Web 2.0, that is, the ability to build the next generation of solutions entirely from Web components. The mechanism of passing-in parameters via the URL defined lightweight Web APIs. Note that in contrast to all earlier software APIs, Web APIs defined in this manner led to loosely coupled systems. Web APIs like those in the table evolved informally and came to be recognized later as programming interfaces that could be used to build highly flexible distributed Web components.

That all of these services heralded publication of a new platform was reflected in the O’Reilly Hacks Series, including: Google Hacks¹⁰; Amazon Hacks ⁴; Yahoo! Hacks³; and eBay Hacks. ²²

The Web had thus evolved from a Web of content to a Web of content embedded with the needed user-in-teraction elements. Content embedded with user interaction evolved into Web applications that could over time be composed exclusively from Web components. Being built this way and living exclusively on the Web, the new software artifacts came to form the building blocks for the next generation of the Web. Together, they define the Web as a platform with certain key characteristics:

Distributed. Web applications were distributed across the network; application logic and data resides on the network, with presentation augmented by the needed user interaction delivered to the browser;

Separable. The distributed nature of Web applications forced a cleaner separation between application logic and the user interface than in the previous generation of monolithic desktop software;