![]() ![]() Finally, Section 4 applies the new method to the Bali- and the 9/11-net and compares the results with those of other methods. Section 3 exemplifies the MEI-concept for a little network of 8 actors. Subsection 2.1 presents all model elements, Subsection 2.2 resumes general knowledge on the concept of maximal entropy (Max-Ent), and Subsection 2.3 develops an index of importance Max-Ent-Index (MEI) for actors. Section 2 provides logical, probabilistic, and information theoretical preliminaries. In this paper, we follow this line and use conditionals to model links between actors but add a new concept to make an actor's importance measureable. In the work of Brenner et al. ( 2017) the new method is applied to a net with 650 actors and 839 conditionals. In such a model for each actor they determine his potential of diffusion and of reception. Rödder et al. ( 2014) model directed links in networks as conditionals: If an actor has a certain knowledge, then also his successors and the successors thereof do. This makes the measure of an actor's importance a local rather than a global quantity of the net structure.Īn up-and-coming method of SNA is based on AI applying a probabilistic concept and an information theoretical inference process. In theorem 1 on page 21 the authors show that the difference of energies is a function of degrees of the removed actor and degrees of his neighbours. The method of Laplacian energy uses Laplace-energies instead of net-efficiencies. This might be dubitable as information flow in a terrorist network does not always follow shortest paths, we feel. All calculations are based on shortest paths to remaining actors. The greater the difference of efficiencies the more important the actor. Latora and Marchiori ( 2002) define the efficiency of a network and compare it to the efficiency after the removal of an actor. the method of Laplacian energy by Qi et al. ( 2013).īoth ideas follow a similar philosophy.the method of critical components by Latora and Marchiori ( 2002).Soon after 9/11 new methods were developed to identify leading members in criminal networks, for example, Katz' centrality is based on parameters to be defined by the analyst and therefore subject to a certain arbitrariness (Brenner et al., 2017 Qi et al., 2013) we will not consider it in the remainder of this paper. All this we find in any SN textbook (Jansen, 2006 Newman, 2012 Scott, 2017). In/Out-degree of vertices actors, shortest paths to other actors, betweenness of actors with respect to others, Katz-centrality as a measure of an actor's prestige are such centrality indices. The value added by applying such techniques is studied by Lauchs et al. ( 2012).Ĭlassical SNA provides some methods to identify centrality of actors in a net. They characterize parameters of particular terrorist networks via graph-theoretical techniques. The permanent threat of terrorist attacks is reflected by the increasing number of scientific articles concerned with this issue, see for example, Koschade ( 2006) Mullins and Dolnik ( 2010). Two types can be distinguished: Whereas terrorists beg for public attention in order to convey their political message, crime syndicates prefer to maintain invisibility. Soon thereafter, such networks were classified as dark networks in Bright et al. ( 2012) Raab and Milward ( 2003). For more details, see also the quoted literature (Baker & Faulkner, 1993 Erickson, 1981 Friedkin, 1983 Sparrow, 1991). In 2002 he analysed 9/11 and fleshed out the difficulties that come up with the investigation of covert networks, that is, incompleteness, difficulty to identify actors, and dynamics. One of the first authors to attend to this subject was Krebs ( 2002). Right after 9/11 scientists began to pick up the issue, to apply existing Social Network Analysis (SNA) methods and to develop new techniques. Analysing terrorist networks that way we can – hopefully – develop a prevention strategy against future attacks. Which information flows took place and what was the leadership system. It is important to know the terrorists, co-perpetrators, helpers, and their netting. ![]() These terrible tidings require cross-border cooperation of intelligence services. Since then we count more than 120 attacks in 29 countries the number of victims exceeds 28,000 – as of May 2019. In the 21st century many people associate the terrible attack on the towers of WTC in 2001 with Islamic terrorism. ![]() Scanning the list of major terrorist incidents in Wikipedia we find umpteen pages of reports on attacks since 1978. ![]()
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