From the Introduction:
The World Wide Web has at least two characteristics that distinguish it from many other shared information spaces:
- The Web is global: the documents on the Web are contributed by and accessed by a very large number of users.
- Supporting ad-hoc exploration is a goal of the Web. Users must therefore be able to get useful information from documents prepared by people whom they don’t know, and with whom they have not coordinated in advance.
Why it is worthwhile to make the web self-describable:
The Web is designed to support flexible exploration of information, by human users and by automated agents.
When self-describing resources are linked together, the Web as a whole can support reliable, ad hoc discovery of information.