Abstract
Social group is a type of mesoscopic structure that connects human individuals in microscopic level and the global structure of society. In this paper, we propose a tag-based model considering that social groups expand along the edge that connects two neighbors with a similar tag of interest. The model runs on a real-world friendship network, and its simulation results show that various properties of simulated group network can well fit the empirical analysis on real-world social groups, indicating that the model catches the major mechanism driving the evolution of social groups and successfully reconstructs the social group network from a friendship network and throws light on digging of relationships between social functional organizations.
1. Introduction
Gathering groups is widespread in societies covering different cultures and different historical periods [1]. Human individuals form associations, organizations and institutions, and there are usually relatively stable members, clear social tags and boundaries in each of these social institutes. In this paper, this type of social institutes is termed as ‘‘social groups’’. Generally, different from the widely-discussed implicit structure termed as ‘‘community’’ [2,3], social group is a type of explicit mesoscopic structure of society because of their clear tags and boundaries. Since these tags usually come from the real-world social functional institutes/organizations, social groups will have strong coincidence with these social institutes/organizations. For example, a user usually would like to join a group whose major members are his/her colleagues or teammates. This correlation actually provides a possible way to investigate the relationships and effective organizations between real-world functional institutes from the group information of online societies. And also, online groups usually are widely used to be a place for information releasing and public discussing, and they therefore play an important role in the spreading of online information and the formation of public opinions.
4. Discussions
The core of the proposed model is the hypothesis that, active users will have more possibilities to join groups, and every user in the friendship network has some tags of interest more or less, and they will create or join groups within their tags of interest. As a minimum model, neglecting several realistic cases that users possibly withdraw from groups, or groups can be dismissed is inevitably only an approximation for the process of real emergence. Nonetheless, to do this would introduce more parameters and cloud the basic result: the tendency of an individual to join a group is not only influenced by its tags of interest, but also crucially related to its current external state in the social environment. The basic hypothesis of the model is verified by the high consistency between the simulation results and the empirical findings. This mechanism provides a heuristic insight to the understanding for both the emergence and the growth of social groups and the reconstruction of social group network from friendship network.
