Although the term suggests a new version of the World Wide Web, it does not refer to an update to any technical specifications, but rather to cumulative changes in the ways software developers and end-users use the Web.
Can we say that an application is using (or what will be right word? compliant with?) Web 2.0 if it:
1. Uses Ajax to update the pages.
2. Uses Flash for graphics which can't be developed in HTML.
3. Publishes RSS feeds.
3. Uses Web Service to make response readable by machine.