social network analysis

I am a big fan of evangelizing the masses about operations research using social networking tools. For this month’s OR blog challenge about social networking, I thought I’d write about social networks themselves.  The real social networks (at least what I know about them).

I first learned about social network analysis (SNA) a few years ago through counter-terrorism applications. They are a mix of graph theory and psychology. Orgnet describes SNA this way:

Social network analysis [SNA] is the mapping and measuring of relationships and flows between people, groups, organizations, computers, URLs, and other connected information/knowledge entities. The nodes in the network are the people and groups while the links show relationships or flows between the nodes. SNA provides both a visual and a mathematical analysis of human relationships.

If you’ve had graph theory, you can imagine that each person is a node and the relationship of interest can be a directed arc or undirected edge. One graph could create a set of (undirected) edges between people who directly talk to one another. Another graph could be defined over the same people but with a directed arc originating at a person who gives the orders and pointing towards someone else who receives orders (remember that I learned about this through counter-terrorism applications? Imagine using SNA to understand how the power hierarchy works in a terrorist group or cult). I’m a little fuzzy about how these different layers of edges describing relationships over the same set of nodes can be used to inform decisions, but that’s probably because a social scientist was explaining this to me, and we weren’t speaking the same language. Most of the time, I see just a single graph describing one layer of interest. In my next blog post, I’ll illustrate five social networks.

SNA would look different if you are, say, identifying how to bring down a terrorist cell or, say, identifying how to effectively market to various FaceBook users to turn a profit. Network measures such as degree centrality, connectivity, degree, and reach can be used to assist in the  decision making process (this book by a mathematical sociologist is helpful). In a terrorist network, SNA is used to identify those who are in power, how power is allocated (e.g., are there many layers in the hierarchy?) and those who are on the periphery who can perhaps be used to infiltrate the organization.

The more I learn about SNA, the more I realize I do not know. It is a hot topic in disciplines from sociology to computer science. I wish I knew more about SNA. One of these days, I’ll attend one of those interdisciplinary SNA conferences. If you have any good pointed for getting started, please let me know.  In the meantime, check for my follow up post on social networks visualized.


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