How much similar are terrorists networks of Istanbul?

Most of terrorist groups cooperate, interchange knowledge, skills and materials used for attacks. Terrorist groups in Istanbul are categorized into three main groups within criminological viewpoint: extreme left (i.e. Marxist) groups, extreme right (i.e. Fundamentalist, Radical Islamist) groups, and separatist (i.e. ethnic, racist) groups. Crime ontology for terrorist groups in Istanbul is created by using their criminal history and choices such as selection of crimes, attacking methods and modus operandi. Terrorist groups of Istanbul are attached to this ontology as nodes connected to their attacks. A similarity measure (COSM) is developed according to this ontology. COSM results for Istanbul terrorist groups performed better than two common similarity measures; cosine and Jaccard. COSM similarity result is presented to domain experts in hierarchical clustering and they gave positive feedback. COSM, which is based on attributes of crimes, can also be applied to other types of social networks for measuring similarity.