What is Web 2.0? Is it the "read-write" web, the mash-ups or is it just a collection of fancy colored applications?
The name Web 2.0 is already two year old and is "invented" by O'Reilly Media. Just recently they (re)published a report where the Web 2.0 definitions are updated. The report "Web 2.0 Principles and Best Practices" describes 8 basic web 2.0 principles. It is written by John Musser, wellknown from his Programmable Web site.
Unfortunately I haven't been able to read the full report but thanks to Dion Hinchcliffe's post on the subject here an abstract of the 8 principles:
Harnessing Collective Intelligence:
Sometimes described as the core pattern of Web 2.0, this describes architectures of participation that embraces the effective use of network effects and feedback loops to create systems that get better the more that people use them.
Data is the Next "Intel Inside":
A phrase that captures the fact that information that information has become as important, or more important, than software, which has become relentlessly commoditized.
Innovation in Assembly:
The Web has become a massive source of small pieces of data and services, loosely joined, increasing the recombinant possibilities and unintended uses of systems and information.
Rich User Experiences:
The Web page has evolved to become far more than HTML markup and now embodies full software experiences that enable interaction and immersion in innovative new ways.
Software Above the Level of a Single Device:
Software like the horizontally federated blogosphere (hundreds of blog platforms and aggregators) or the vertically integrated iTunes (server farm + online store + iTunes client + iPods) are changing our software landscape.
Perpetual Beta:
Software releases are disappearing and continuous change is becoming the norm.
Leveraging the Long Tail:
The mass servicing of micromarkets cost effectively via the Web is one of the primary "killer business models" made possible by the Internet in its present form.
Lightweight Software/Business Models and Cost Effective Scalability:
Everything from Amazon's S3, to RSS, to Ruby on Rails are changing the economics of online software development fundamentally, providing new players powerful new weapons against established players and even entire industries.
Dion tries to clarify the 8 principles in a drawing but that wasn't really succesfull. On the other hand the description of the principles gives a very complete picture of what is ment by Web 2.0 now. I emphasize on now because in the original article by Tim O'Reilly the principles were described slightly different.
New in this description is the principle "Rich User Experiences". Not being in the original document was a surpise to me. I thought user experience was one of the key principles of Web 2.0. Ah well, it just caught up in this version 
.
A while ago I was talking to Alex Thissen about Web 2.0 and it was surprising that we both were describing different parts of Web 2.0. We were both incomplete but still more accurate than Dennis van der Stelt in his blogpost.
I'm glad John Musser wrote this article it gives a complete picture of the current Web 2.0 but I wonder if we will be calling it Web 2.0 two years from now ...