What is the difference between a Search Agent, the topic of this post, and a search engine? A search engine maintains its own index to return search results in a matter of milli-seconds, and assumes that it can fulfill the user’s information needs by itself. There are now many first-, second- and third-level search engines, general or specialised, on the Internet. A Search Agent takes more time to answer to the user, maybe a few minutes, but yields more varied or less common results.

The social graph is one of the important new concepts of our time. It can be explored from page to page on Twitter or Facebook. It is very interesting for users to explore who knows who, even if you might not grasp how well they know each other. Sometimes the social graph is actually shown as an explicit graph with nodes and edges. But as people usually have 100s of contacts, it can be very hard to grasp what is shown at first glance.