Web 2.0

Web 2.0, a phrase coined by O'Reilly Media in 2003 and popularized by the first Web 2.0 conference in 2004, refers to a perceived second generation of web-based communities and hosted services — such as social-networking sites, wikis and folksonomies — which facilitate collaboration and sharing between users. O'Reilly Media titled a series of conferences around the phrase, and it has since become widely adopted.

Although the term suggests a new version of the World Wide Web, it does not refer to an update to Web technical specifications, but to changes in the ways systems developers have used the web platform. According to Tim O'Reilly, "Web 2.0 is the business revolution in the computer industry caused by the move to the internet as platform, and an attempt to understand the rules for success on that new platform."

Some technology experts, notably Tim Berners-Lee, have questioned whether one can use the term in a meaningful way, since many of the technology components of "Web 2.0" have existed since the beginnings of the internet.

The complex and evolving technology infrastructure of Web 2.0 includes server-software, content-syndication, messaging-protocols, standards-based browsers with plugins and extensions, and various client-applications. These differing but complementary approaches provide Web 2.0 with information-storage, creation, and dissemination capabilities that go beyond what the public formerly expected of websites.

A Web 2.0 website may typically feature a number of the following techniques:

1. Rich Internet application techniques, optionally Ajax-based
2. CSS
3. Semantically valid XHTML markup and the use of Microformats
4. Syndication and aggregation of data in RSS/Atom
5. Clean and meaningful URLs
6. Extensive use of folksonomies (in the form of tags or tagclouds, for example)
7. Use of wiki software either completely or partially (where partial use may grow to become the complete platform for the site)
8. Use of Open source software either completely or partially, such as the LAMP solution stack
9. XACML over SOAP for access control between organisations and domains
10. Weblog publishing
11. Mashups
12. REST or XML Webservice APIs

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