Directed vs. Nondirected Links

Barabasi makes a very important distinction when discussing networks: directed links versus nondirected links.

Directed links, he explains, is when A --> B --> C --> D, but it is not necessarily the same in reverse. The links only work when traveling one way. Nondirected links have the ability to complete the cycle, and also to reverse the steps as well.

I think this is an important distinction to make, because it affects how we perceive the strength and connectedness of networks. The network and linking of the Internet, for example, is a series of directed links, which means that while we can get from one page to any other page in 19 clicks, we can't necessarily take the same path back to where we started. Barabasi points out that this also occurs in biology with the foodchain.

Social networks are a series of nondirected links. By the mere fact that Person A has a relationship to Person B, Person B clearly knows Person A as well. (The biological translation of this, as Barabasi provides, would be protein interactions.)

Understanding the differences between directed and nondirected links within networks is an important consideration when establishing a new network, such as our YouthMap.