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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>Methodological Approach to Agent-Based Modeling of Social Networks</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Olga Vasylieva</string-name>
          <email>olga.vasiljeva37@gmail.com</email>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Borys Butvin</string-name>
          <email>butvin_bl@ukr.net</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Yuriy Shtyfurak</string-name>
          <email>yura.shtyfurak@gmail.com</email>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Central Research Institute of the Armed Forces of Ukraine</institution>
          ,
          <addr-line>28b Povitroflotskyi Avenue, Kyiv, 03049</addr-line>
          ,
          <country country="UA">Ukraine</country>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>Foreign Intelligence Service of Ukraine</institution>
          ,
          <addr-line>24/1, Nahirna Street, Kyiv, 04107</addr-line>
          ,
          <country country="UA">Ukraine</country>
        </aff>
        <aff id="aff2">
          <label>2</label>
          <institution>National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”</institution>
          ,
          <addr-line>37, Prosp. Peremohy, Kyiv, 03056</addr-line>
          ,
          <country country="UA">Ukraine</country>
        </aff>
      </contrib-group>
      <abstract>
        <p>The article considers social networks as an environment with a complex structure, which is dynamically changing and difficult to analyze. Here is presented the basic methodological approaches for application in the theoretical analysis of social networks. Further, it is proposed to apply the method of agent-based modeling, which today, in the authors' opinion, can be the most adaptive for modeling internal processes of such dynamic social systems as social networks. The most popular software tools for building agent-based models are described and the software AnyLogic developed by XJTeknologies, which has a number of competitive advantages, is highlighted as the most versatile and multifunctional.</p>
      </abstract>
      <kwd-group>
        <kwd>1 Agent-based modeling</kwd>
        <kwd>social networks</kwd>
        <kwd>information influence</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <p>Aim of the study. Modeling of social processes
such as information influence in the social
networks by applying agent-based modeling and
selecting the most appropriate software tool.</p>
      <p>Today, the information influence on human
resource has a special place in the system of
management decision-making, the political
component, the development of business
processes, etc. This has become possible due,
firstly, to the rapid development of digital
technologies, including those used for data
dissemination and information exchange, the
creation and development of new types of
information resources, increased access to
information for all segments of the population.
Second, the large masses of information that
circulates in cyberspace, is open, easily accessible
and such that with the help of technology,
linguistics, psychology and other knowledge can
become a tool to manipulate human communities.</p>
      <p>The most acceptable instrument for
informational influence in terms of its own
structure and the availability of appropriate target
audiences are social networks today. The term
"virtual (network) community" was firstly
introduced in 1993 by G. Rheingold, who defined
it this way: "Virtual communities are social
associations, growing out of the Web, when a
group of people maintain an open discussion long
enough and humanly enough to form a network of
personal relations in cyberspace" [1].</p>
      <p>Social networks today are an important
element of the structure of modern society, and
their influence extends to various spheres of
human activity: production, daily life, culture,
politics, etc. They perform communication,
informational, entertaining, socializing functions
in the society; they provide opportunities for
selfexpression, exchange of information and
experience, without any age, professional or any
other restrictions [2]. The statistics are provided
below demonstrate significant penetration of
social networks in the life of modern human
society.</p>
      <p>
        For example, statistics of social networks in
2021 showed that 42% of the world population
that is a colossal 3.2 billion people - use social
networks. The number of social network users has
increased by more than 13% over the last year,
with almost half a billion new users registered
before 2021. On average, more than 1.3 million
new accounts appeared every day in 2020, that's
about 15.5 new users per second, according to the
Digital Global 2021 report [
        <xref ref-type="bibr" rid="ref1">3</xref>
        ].
      </p>
      <p>A social network is a set of agents (vertices)
that can interact with each other, and the
connections between them are social. From a
formal point of view, such networks are dynamic
social systems, it is convenient to present them in
the form of graphs and apply the appropriate
mathematical apparatus for their analysis.</p>
      <p>This is what determines the relevance of
applying methodological approaches for
modeling such systems in order to further predict
various social processes in networks, including
information influence.</p>
      <p>
        Since formalized models of information
dissemination process in social networks are
actually absent, taking into account their inherent
subjective uncertainty, modeling the processes
that occur in them, as well as modeling social
network itself turns into a weakly formalized
problem [
        <xref ref-type="bibr" rid="ref2">4</xref>
        ].
      </p>
      <p>
        As a first step, we should consider the
methodological approaches that are used to
analyze social networks. They differ from
traditional approaches in sociological sciences.
The postulate that the attributes of individual
actors are less important than the relationships and
connections with other actors in the network
comes to the fore. That is, the attributes of
individual actors - friendliness or unfriendliness,
level of intelligence - begin to play no major
role [
        <xref ref-type="bibr" rid="ref3">5</xref>
        ].
      </p>
      <p>
        Currently there are four main methodological
approaches to the analysis of social networks:
1. Structural – emphasizes the geometric
shape and intensity of interactions (weight of
edges). All actors are viewed as vertices of a
graph, which influence on the configuration of
edges and other actors in the network. Special
attention is paid to the mutual arrangement of
vertices, centrality, and transitivity of
interactions [
        <xref ref-type="bibr" rid="ref4">6</xref>
        ].
2. Dynamic – attention is focused on
changes in the network structure over time.
The reasons of disappearance and appearance
of edges of a network; changes of structure of
a network in case of external influences;
stationary configurations of a social network
are studied [
        <xref ref-type="bibr" rid="ref4">6</xref>
        ].
3. Normative – studies the level of trust
between actors, as well as norms, rules and
sanctions that affect the behavior of actors in
the social network and the processes of their
interaction. In this case, the social roles
associated with a particular edge of the
network are analyzed [
        <xref ref-type="bibr" rid="ref4">6</xref>
        ].
4. Resource – considers the actors' ability to
attract individual and network resources to
achieve certain goals and differentiates actors
being in identical structural positions of the
social network, according to their resources.
Individual resources can be knowledge,
prestige, wealth, ethnicity, gender (gender
identity). Under network resources understand
influence, status, information, capital [
        <xref ref-type="bibr" rid="ref4">6</xref>
        ].
      </p>
      <p>
        In order to involve all four mentioned
approaches of social network analysis, taking into
account both the structure of dynamic system and
its individual actors, defining their interaction,
certain rules of the game, as well as giving them
certain characteristics, the authors proposed to
consider such method of simulation modeling as
Agent-Based Modeling [
        <xref ref-type="bibr" rid="ref5">7</xref>
        ].
      </p>
      <p>Agent-based modeling is a simulation method
that examines the behavior of decentralized
autonomous agents, their interaction (both
individual agents and collective, such as
organizations or groups) and how such behavior
determines the behavior of the entire system as a
whole. It combines elements of game theory,
complex systems, emergence, computational
sociology, multi-agent systems, and evolutionary
programming. It’s used in noncomputational
scientific fields including biology, ecology, and
social sciences.</p>
      <p>Agent-based modeling is used to analyze
decentralized systems that are quite large, have
heterogeneous structures, and are dynamically
changing: old connections die off and new ones
appear. That is why this method is effective to
study the process of spreading of information
influence in social networks.</p>
      <p>To create an agent-based model, all actors are
viewed as separate agents. According to the
structural approach, the social network can be
viewed as vertices with certain connections
between them. The network structure of the model
is dynamic, it is a kind of system that is
selfcreated, the elements of which appear and die. In
such a system, the rules of behavior of each of the
agents and their social roles are also defined.
Finally, each of the agents is given a certain pool
of personal characteristics, which determines the
resource approach.</p>
      <p>Considering the paradigms of system
simulation modeling (Figure 1)
it can be concluded that agent-based modeling
is the most multiple-purpose one. In contrast to
discrete event modeling, which is consonant with
the low and medium abstraction level, and the
system dynamics approach with a high abstraction
level, agent-based models can be both very
detailed, when agents represent physical objects,
and extremely abstract, when competing
companies or state governments are modeled
using agents.</p>
      <p>The main difference between the agent-based
approach and the first two is the bottom-up
construction of the model. Dependencies between
aggregated quantities are not set on the basis of
knowledge about the real world, but are obtained
in the process of modeling individual behavior of
tens, hundreds or thousands of agents, their
interaction with each other and with objects,
which are modeling the environment.</p>
      <p>The advantages of the agent-based approach
include: the absence of determinacy in the
behavior of the system at the global level that can
lead to new hypotheses about its functioning
during model simulation; realism and flexibility
in describing the system, the ability to model the
most complex nonlinear feedbacks and to use any
required level of detail and abstraction. In
agentbased modeling, there are no restrictions on the
heterogeneity of model elements; but there is
possibility to simulate communication and
information exchange [8].</p>
      <p>During simulation experiments, computational
complexities can arise because agent-based
models on average require more hardware and
software power to run simulations than system
dynamics or discrete event simulations.
Agentbased simulations can be implemented on small
desktop computers, or using large clusters of
computers, or any variation between the first two.</p>
      <p>Desktop agent-based models can be simple
and used mostly to teach how to model using
agents, test agent-based model development
concepts, and analyze the results. Desktop utilities
include spreadsheets, particularly Excel, and
mathematical computing systems such as
Mathematica and MATLAB.</p>
      <p>
        Large-scale agent-based models extends the
capabilities of simple agent-based desktop models
and allows a larger number of agents (thousands
to millions) to participate in complex interactions.
Large-scale agent-based modeling is usually
performed using dedicated modeling
environments that include a time-based scheduler,
communication mechanisms, flexible agent
interaction topologies, a wide variety of devices
for storing and displaying agent state [
        <xref ref-type="bibr" rid="ref6">9</xref>
        ].
      </p>
      <p>Due to the fact that the agent-based approach
emerged in the 1990s in the U.S. university
environment, so far most of the tools are intended
for academic and educational purposes, and are
not commercial products in full.</p>
      <p>One of the most popular developments of this
type is the Swarm environment. It’s a collection
of C language libraries created at the Santa Fe
Institute. The most famous commercial tools are
RePast, AnyLogic, NetLogo and MASON.</p>
      <p>MASO is a fast multi-agent modeling toolkit
in Java that was developed as a framework for a
wide range of multi-agent modeling tasks, from
swarm robotics to machine learning and socially
complex environments. MASON makes a careful
distinction between models and visualization,
allowing models to be dynamically separated
from or attached to visualizers, and platforms to
be changed at runtime. MASON is a collaborative
effort between the Computer Science Department
at George Mason University and the Center for
Social Complexity at George Mason University.
One of interest sources is social and biological
models, particularly models of economics, land
use, politics, and population dynamics [10].</p>
      <p>The REcursive Porous Agent Simulation
Toolkit (Repast) is the open and free source of
libraries for large-scale agent-based modeling.
Repast supports the development of extremely
flexible agent-based models and is used in social
process modeling. Users build their model by
incorporating components from the Repast library
into their programs or by using visual Repast for
the Python Scripting environment.</p>
      <p>
        Repast has a sophisticated built-in scheduler
that supports discrete-event modeling and allows
using a large set of communication mechanisms
with a variety of interaction topologies and
includes a full set of utilities for storing and
displaying agent states. The system also includes
utilities for automatic integration with both
commercial and freely available geographic
information systems (GIS). Integration with
commercial GIS includes automatic connection to
widely used geographic information systems such
as ESRI and ArcGIS. Moreover, since Repast is
based on the Java language, the Microsoft .NET
platform and Python scripts, it is fully
objectoriented [
        <xref ref-type="bibr" rid="ref6">9</xref>
        ].
      </p>
      <p>Swarm was the first agent-based development
environment. First launched in 1994 by Chris
Langton at the Santa Fe Institute Swarm is an
open source and free set of libraries and is
currently maintained by the Swarm Development
Group (SDG). The Swarm modeling system
consists of two core components. The kernel
components run simulation code written in
general-purpose language Objective-C, Tcl/Tk,
and Java. Unlike Repast, the Swarm scheduler
only supports time progression at fixed intervals.
Swarm supports a full set of communication
mechanisms and can simulate all major
topologies. Swarm includes a good set of utilities
for storing and displaying agent states. Since
Swarm is based on a combination of Java and
Objective-C, it is object-oriented. But this mix of
languages causes some difficulties with
integration into some large-scale development
environments, such as Eclipse [10].</p>
      <p>
        NetLogo is another cross-platform
agentbased simulation environment that is widely used
and supported. Originally based on the StarLogo
system, NetLogo adapts agent-based systems
consisting of a combination of live and software
agents. It is ideal for modeling complex systems
containing hundreds or thousands of agents
interacting simultaneously. It allows users to
explore the relationship between micro-level
agents and behavior at macro-level. The language
has been developed heavily influenced by Logo
and is intended for users from many disciplines
economists, anthropologists, physicists and many
others. The interface allows users to interact with
variables within a simulation and visualize results
without having to look at the code itself. The
language is similar to English, which makes it
easy for a non-specialist to understand the
functionality of each line of code. In addition,
NetLogo contains an extensive library of models
that includes example programs from a wide
variety of disciplines, which is very useful for
teaching and learning purposes [
        <xref ref-type="bibr" rid="ref7">11</xref>
        ].
      </p>
      <p>AnyLogic is a development of XJTeknologies,
which has found wide application among users.</p>
      <p>The competitive advantage of AnyLogic is the
support of all three simulation paradigms and the
ability to use them within a single model.
AnyLogic also features a powerful productive
kernel that can simulate the behavior of millions
of agents; rich animation and graphical model
description capabilities; support for various types
of experiments, including sensitivity analysis,
Monte Carlo method, built-in OptQuest
optimizer; integration capabilities with databases,
ERP and CRM systems; a set of library objects
from logistics, business processes, and pedestrian
dynamics areas.</p>
      <p>
        During developing an agent-based model in
AnyLogic, the user inputs agent parameters
(people, companies, assets, projects, vehicles,
cities, animals etc.), defines their behavior, places
them in an environment, establishes possible
connections and then runs the simulation. The
individual behavior of each agent forms the global
behavior of the simulated system [
        <xref ref-type="bibr" rid="ref8">12</xref>
        ].
      </p>
      <p>There are also some "templates" that simplify
model creation and are included in AnyLogic:
- standard architecture;
- agent-based synchronization ("steps");
- state (continuous or discrete);
- mobility and animation;
- agent-based connections (networks, e.g.,
social networks) and communication;
- dynamic creation and destruction of agents.</p>
      <p>AnyLogic provides a graphical language that
greatly simplifies the creation of agent-based
models:
 statecharts for specifying agent behavior;
 the action diagram for describing
complex algorithms;
 the "Environment" element is used to
describe the "world", in which agents "live"
and to collect various statistics;
 the "Event" element is used to describe
random or periodically occurring events.</p>
      <p>It should be noted that this software was used
in scientific studies regarding the prediction of the
spread of Covid_19 infection in dynamic social
groups, which are immanently identical to social
networks. These studies showed high reliability of
the obtained results: the experimental results
coincided with the real ones. Fig.2 shows an
example of the agent-based modeling application
- model structure of the Covid_19 infection spread
study on a local multiplicity (N = 10,000) of
agents.</p>
      <p>It should also be noted that these tools allow
describing almost all behavioral features of
agents. Moreover Java language allows
simulating any special behavior or logic. Also the
specific character of AnyLogic is possibility to
combine agent-based models with discrete-event
and system-dynamic models.</p>
      <p>That is why the authors of the article propose
to use AnyLogic software for modeling social
networks.</p>
    </sec>
    <sec id="sec-2">
      <title>2. Conclusions</title>
      <p>Therefore, agent-based modeling allows
creating a model of a social network, where, for
example, social processes such as distribution of
certain information take place, that is information
influence is carried out, and all basic
methodological approaches to the analysis of
social networks are applied. Also, by analyzing
the comparative characteristics of the most
popular agent-based modeling platforms, it was
determined that the most adaptive and
multiplepurpose, as well as supporting a pool of platforms
for optimization, is the AnyLogic platform, which
among other things is designed to model such
complex dynamic systems as social networks and
their internal processes, such as the distribution of
information influences.
3. References</p>
    </sec>
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