We address the problem of using semantic technology for capturing informal organizational structure by means of a light-weight ontology. The idea is to support knowledge management in analyzing communication between people in an organization. As an example we use social network of a mid size research institution obtained based on e-mail communication. We propose an approach consisting of five major steps that enable transformation of the data from a given e-mail transactions recordings to a

more »

... t-weight ontology estimating structure of the organization. The experimental evaluation shows that on our e-mail transaction data the obtained organizational structure closely corresponds to the formal organizational structure. We conclude that the proposed approach is useful and applicable in real life situations where the goal is to model social structures based on communication records.