Research Article
Extraction of Multilayered Social Networks from Activity Data
Katarzyna Musial,
1
Piotr Bródka,
2
PrzemysBaw Kazienko,
2
and JarosBaw Gaworecki
3
1
School of Natural and Mathematical Sciences, Department of Informatics, King’s College London, London WC2R 2LS, UK
2
Institute of Informatics, Wrocław University of Technology, Wyb. Wyspi´ anskiego 27, 50-370 Wrocław, Poland
3
Research & Engineering Center Sp. z o.o., Ulica Strzegomska 46B, 53-611 Wrocław, Poland
Correspondence should be addressed to Przemysław Kazienko; kazienko@pwr.wroc.pl
Received 23 January 2014; Accepted 6 March 2014; Published 2 July 2014
Academic Editors: H. R. Karimi, Z. Yu, and W. Zhang
Copyright © 2014 Katarzyna Musial et al. is is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
cited.
e data gathered in all kinds of web-based systems, which enable users to interact with each other, provides an opportunity to
extract social networks that consist of people and relationships between them. e emerging structures are very complex due to the
number and type of discovered connections. In web-based systems, the characteristic element of each interaction between users is
that there is always an object that serves as a communication medium. is can be, for example, an e-mail sent from one user to
another or post at the forum authored by one user and commented on by others. Based on these objects and activities that users
perform towards them, different kinds of relationships can be identified and extracted. Additional challenge arises from the fact
that hierarchies can exist between objects; for example, a forum consists of one or more groups of topics, and each of them contains
topics that finally include posts. In this paper, we propose a new method for creation of multilayered social network based on the
data about users activities towards different types of objects between which the hierarchy exists. Due to the flattening, preprocessing
procedure of new layers and new relationships in the multilayered social network can be identified and analysed.
1. Introduction
Nowadays, for the first time, we have possibility to process
big data about interactions and activities of millions of
individuals gathered in all sorts of web-based systems. Com-
munication technologies allow us to form large networks,
which in turn shape and catalyse our activities. Due to
their scale, complexity, and dynamics, these networks are
extremely difficult (or impossible) to analyse in terms of
traditional social network analysis methods. e analysis of
the network data is at the very early stages and requires a lot
of efforts in both developing tools and approaches to tackle
it as well as understanding the nature and functioning of
networks extracted from this data. e process of network
creation is not as straightforward as it seems to be. In the web-
based systems, users can interact with each other via different
communication channels and utilize various services. is
implies that the relationships between users can be extracted
based on both direct and indirect communications. e
former one is, for example, sending emails or video calls
where information is passed directly from one person (group
of people) to other(s), whereas to the latter we can count in,
for example, commenting objects in the multimedia sharing
systems or using the same tags to describe the objects. In
both situations there are objects (e.g., email, photo, and tag)
that serve as medium in communication between users. e
types of these objects differ depending on the web system;
for example, at the Internet forum the objects are groups of
topics, topics, and posts while in the email service it will be
a single message. Additionally, within a single system, the
hierarchies of objects can exist.
Extraction of a social network in the environment where
users interact with each other using different objects, which
create hierarchies, is the main contribution of this paper.
In order to perform this task first the hierarchical presocial
network (HPSN), where relation between users and objects
and between objects exists (Section 5), must be created.
Aſter that, the flattening process, in which the hierarchy of
objects is removed, is performed (Section 6). As a result, the
flat presocial network (FPSN) is obtained where the only
Hindawi Publishing Corporation
e Scientific World Journal
Volume 2014, Article ID 359868, 13 pages
http://dx.doi.org/10.1155/2014/359868