Detecting Patterns in Complex Social Networks

By Roland Piquepaille

So-called social networking is very popular these days, as shows the proliferation of services like Friendster, Orkut and dozens of others. But do the companies behind these services have any idea of what is hidden inside their complicated networks? When these networks reach a size of millions of users, it's not an easy task. A researcher at the University of Michigan is trying to help, with a new method for uncovering patterns in complicated networks, from football conferences to food webs.

Let's start with a spectacular representation of the Internet (Credit: Bill Cheswick, Lumeta Corp.). A larger version is viewable here.

A representation of the Internet
"The structure of those networks can tell you quite a lot about how the systems work, but they're far too big to analyze by just putting dots on a piece of paper and drawing lines to connect them," said Mark Newman, an assistant professor of physics and complex systems at the University of Michigan.
One challenge in making sense of a large network is finding clumps -- or communities -- of members that have something in common, such as Web pages that are all about the same topic, people that socialize together or animals that eat the same kind of food.

Newman and his collaborators developed a new method for finding communities in these large networks.

The way most people have approached the problem is to look for the clumps themselves -- to look for things that are joined together strongly," said Newman. "We decided to approach it from the other end," by searching out and then eliminating the links that join clumps together. "When we remove those from the network, what we're left with is the clumps."

They applied their method on networks with well-known structures, such as college football conferences. They also used it for networks with less-known structures, such as a food web of marine organisms living in Chesapeake Bay.

Here is what looks like a food web at Little Rock Lake (Credit: Mark Newman).

A food web at Little Rock Lake

You'll find more illustrations in this gallery of network images.

And for more information about social-network mapping tools, you can look at two previous columns, here or there.

Sources: University of Michigan press release, February 15, 2004; and various websites


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