Bob Wyman writes:
There are many who have commented on the differences between the “visible web” and the “hidden web.” The hidden web is commonly defined as “the publicly accessible pages on the World Wide Web that are not indexed by search engines.” To these two webs (visible and hidden) we should add a third web — the Gray Web. By this I mean publicly accessible pages on the web that are not usefully indexed by search engines today. The Gray Web is both dark and visible at the same time. The Gray Web is composed of the structured data and the timely or rapidly changing data not well supported by most of today’s search engines.
With Structured Blogging, we’ll be able to post structured items in any of millions of blogs or web sites and have those items recognized, indexed, and searched on any number of search sites — just like HTML pages are today. No longer will we need to rely on going to a small number of centralized, walled-garden, closed sites like MeetUp, eBay, Monster, or EVDB to publish or search for the kind of information that requires structure. Common search engines like Google, Yahoo! and PubSub will be able to usefully index this data. In the future, as search engines come to better support structured data, we will all benefit as the Gray Web grows smaller and the visible web grows larger.