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<article xmlns:xlink="http://www.w3.org/1999/xlink">
  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>Adaptive and Personalized e/m-Learning : Approaches and Techniques</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Learning</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff1">1</xref>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Mahnane Lamia LRS Laboratory Badji Mokhtar University Annaba-</institution>
          <country country="DZ">Algeria</country>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>Mohamed Hafidi LRS Laboratory Badji Mokhtar University Annaba-</institution>
          <country country="DZ">Algeria</country>
        </aff>
        <aff id="aff2">
          <label>2</label>
          <institution>Ouissem Benmesbah LRS Laboratory Badji Mokhtar University Annaba-</institution>
          <country country="DZ">Algeria</country>
        </aff>
      </contrib-group>
      <abstract>
        <p>- Adaptive and personalized approaches within e/m learning systems enable adapting learning Objects (LOs) and process to the different needs and contexts, to help the learners in improving their knowledge or skills. In this paper, we review the recent research on learning adaptation to pursue two goals: First is to unify the classification of adaptation types; the second is to study the different approaches and techniques used to implement the learning adaptation in its two main types : adaptation of the LOs selection and adaptation of the LOs sequencing.</p>
      </abstract>
      <kwd-group>
        <kwd>Adaptive e/m adaptation</kwd>
        <kwd>Adaptation by selection</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>I. INTRODUCTION</title>
      <p>With the rapid development of information technology in
education and learning field, researchers have created myriad
learning resources. It has been a difficult task for learners to
find suitable learning resources from the Internet. Without
effective adaptation, irrelevant resources will lead to
learners’ cognitive overload and affect learning outcomes.
Therefore, learning systems need to be adapted to the
learners' context and needs.</p>
      <p>An adaptive learning environment provides personalized
learning resources and processes to the learner through
selfdirected study. An adaptive learning model can be
subdivided basically into a learner model, domain model,
and adaptive engine. In such environment, the adaptive e/m
learning system should adapt its services to a learner’s needs
and context. The purpose of adaptation is to optimize the
relationship between the learner context and learning
content; hence, the learning outcome could be obtained with
minimum time and interaction and could also increase the
learner satisfaction [1].</p>
      <p>Even though academic research on adaptive learning
environments has increased, the field lacks a comprehensive
literature analysis of the classification of the adaptation
types, and the most used approaches and algorithms used to
implement every type of adaptation.</p>
      <p>This paper presents a study of learning adaptation in e/m
learning systems from 2008 up to 2019. It aims to specify:</p>
    </sec>
    <sec id="sec-2">
      <title>Rq1- What should be adapted?</title>
    </sec>
    <sec id="sec-3">
      <title>Rq2- How it should be adapted?</title>
      <p>The rest of this paper is structured as follows: Section 2
describes the main types of learning adaptation. Section 3
collects the most used approaches and algorithms used to
implement the adaptation of the learning content and the
learning path. Finally, Section 4 presents the conclusion of
the work.</p>
      <p>II. OVERVIEW OF THE LEARNING ADAPTATION</p>
      <p>CLASSIFICATION</p>
      <p>The first research question can be answered by presenting
a general classification of adaptation types used in the field
of e/m-learning. Several researchers have addressed the
adaptation type classification applied in the field of adaptive
learning, but these classifications are slightly different. In
this section we will study them and propose a new
classification.</p>
      <p>Sampson [2] identifies three main categories of
adaptation related to educational resources within adaptive
and personalized learning systems: -Selection Adaptation:
This type of adaptation deals with selecting appropriate
learning objects LO based on different selection criteria
derived from learners’ contextual elements. -Presentation
Adaptation : considers that LOs is adaptively structured for
access via mobile devices by taking into account parameters
related to the learners’ type of mobile device, the learner’s
profile (including learner’s preferences and learning style),
Parameters related with learner’s location, physical
conditions and learner’s temporal information. -Sequencing
Adaptation : This type of adaptation rearranges or reorders
the navigation and sequencing possibilities of different LOs
that are linked to each other towards creating personalized
learning paths by taking into account different criteria
derived from learners’ contextual elements (previous
knowledge, availability and current location, Time,…).</p>
      <p>Premlatha defines two adaptation types: adaptive
presentation at the content level and adaptive navigation
support at the link level [1].</p>
      <p>El jenati [3] adopts in his work three types of adaptation :
-Adaptive content: The adaptation of the content is based on
the selection of the adequate pedagogical content which take
into account the learner’s context. Some learners may wish
to get a simple version of the content and others may wish to
get a detailed version. - Adaptive navigation: The Adaptive
navigation allows to learners to find their paths by adapting
the presentation of links to the objectives, knowledge and the
preferences of the learner. -Adaptive presentation: The
adaptive presentation is to adapt the visual presentation to the
preferences and needs of the learner. Some learner can easily
read the presented music score and will know how it sounds,
but others will want an audio version.</p>
      <p>The work presented in [4] focused on various e-learning
problems, from these problems, we can extract a set of
adaptation types: -Learning path generation (LPG): focused
on providing a sequence of learning object materials to the
learners -Object recommendation (OR): Allows an adaptive
selection of LOs and -Personalization of content (POC):
specifies what learning objects are needed for the course
established for a specific learner requiring a specific subject.</p>
      <p>Based on the works presented above, we can define two
main classes of adaptation:
</p>
      <p>Adaptation related to the content: It can be divided into
two sub categories:
- Adaptation of the content selection: Proposes a set of
LOs adapted to the learner’s needs and contexts.</p>
      <p>-Adaptation of the content presentation: Different
presentation forms of educational resources include [2]:
Changing the format for the same type of educational
resource (e.g. wav files to mp3 files), Changing the type of
the educational resource (e.g. -Changing the dimensions of
the educational resource (e.g. scaling down or scaling the
dimensions of the educational resource).
</p>
      <p>Adaptation related to the learning path: It aims to find the
learners’ paths while learning in e-learning system by
adapting the learner preferences, learning styles, and
other characteristics of an individual user.</p>
      <p>In this work, we have excluded the adaptation of the
Content presentation, that’s because we are convinced that
the adaptation of the format and the scale can be avoided and
replaced by a selection adaptation which will include the
Content selection with the most appropriate format and scale
according to the learner's learning style and / or
characteristics of his mobile while being based on the density
and high availability of resources pedagogical models in the
LO Repositories, which store several format of the same
content. So in our study, we will focus only on two major
types of adaptation that are: adaptation by selection and
adaptation of the learning path.</p>
      <p>In the following sections, we will move to the second
research question which is "How pedagogical content should
be adapted? And this, by studying the different approaches,
techniques or algorithms used to achieve each type of
adaptation.</p>
      <p>III. OVERVIEW OF THE LEARNING ADAPTATION APPROCHES</p>
      <p>AND ALGORITHMS</p>
      <sec id="sec-3-1">
        <title>A. Adaptation of LOs Selection:</title>
        <p>Table 1 presents a collection of works that propose an
adaptation by selection, these works can be divided into two
categories: the first implements only the adaptation by
selection, which consists of selecting LOs adapted to the
needs and/or context of the user. The second category aims at
performing adaptation by selection as the first phase
followed by a second phase which is the adaptation of the
LO s sequencing. In this second case, we are limited to study
the technique or the algorithm used in the first phase of the
adaptation.</p>
        <p>Among 16 works collected in Table 1, 9 works perform
the adaptation by selection based on the learner model
[6-39-13-14-16-17-18-19]. This model includes information such
as learner profile, learning needs or objective, learning style,
knowledge level, ..., this means that these works have not
integrated the notion of the context which constitutes what is
called a context model, this model must integrate information
such as the location of the learner, time, the environmental
characteristics (noise level, lighting level), device
characteristics…etc [5-7-8-10-11-12-15] .</p>
        <p>Arriving to the second research question:“How the
learning content should be adapted’. The answer to this
question consists to find the most applied approaches and
algorithms in the learning adaptation field.</p>
        <p>As can be seen from Table 1, the majority of the works
depends on Ontologies enriched with Semantic Web Rule
Language (SWRL). Ontologies as a key and important
component of semantic web technologies are used to
represent knowledge about e-learning domain. SWRL is a
strong mechanism for inferring new relations and knowledge
which cannot be reached using ontologies
[5-6-3-7-8-9-1011].</p>
        <p>Another category of works is based on ontology
modeling of the context and the Leaning domain but it is not
based on rules but rather on Algorithms [12-13-14-15]:</p>
        <p>
          Erazo-Garzón in [
          <xref ref-type="bibr" rid="ref12">12</xref>
          ] used semantic search (keywords)
and route algorithms applied to ontological models due to
their expressiveness and extensible architecture, to determine
with precision the concepts and semantic relations that exist
among academic and contextual information. In [
          <xref ref-type="bibr" rid="ref13">13</xref>
          ] and
[
          <xref ref-type="bibr" rid="ref14">14</xref>
          ], Semantic learning objects search is proposed, it is based
on the query expansion of the user query and uses the
semantic similarity to retrieve semantic matched learning
objects. In [
          <xref ref-type="bibr" rid="ref15">15</xref>
          ], a novel context-aware mobile learning
application is proposed to encourage and promote Hadith
learning, three dimensions (location, time and profile) of user
context are implemented, context-filtering based regular
expression and ontology matching-recommending techniques
are used to match appropriate hadith on learner’s context.
        </p>
        <p>The third category of works applied Evolutionary
computing algorithms (EC) to implement the adaptation by
selection:</p>
        <p>
          Latha in [
          <xref ref-type="bibr" rid="ref16">16</xref>
          ] presents an evolutionary approach for
tuning the parameters required for personalizing the learning
content delivery. The compatibility level of the LO are tuned
with respect to the learning style of the learner; the
complexity levels of the learner are tuned based on the
feedbacks from similar learners and the knowledge levels of
the learners are tuned with respect to the complexity level of
the learning objects. The interactivity levels of the learners
are tuned based on the behavior of the learners during the
learning process. For that purpose Compatible Genetic
Algorithm (CGA) is applied.
        </p>
        <p>
          Yang [
          <xref ref-type="bibr" rid="ref17">17</xref>
          ] in his work, proposed an Attributes-based Ant
Colony Optimisation System (AACS) to help learners find
an adaptive learning object more effectively by considering
the relationship between learner attributes (e.g. learning
style, domain knowledge) and LO’s attributes. For that
AACS algorithm is proposed, it is derived from an extension
of the Ant colony system that updates the trails’ pheromones
from different knowledge levels and different styles of a
group’s learners to create a powerful and dynamic learning
object search mechanism.
        </p>
        <p>
          In Dwivedi [
          <xref ref-type="bibr" rid="ref18">18</xref>
          ], the author develops learning path
recommendation framework by employing course
generator’s advice and evolutionary approach namely a
variable length genetic algorithm (VLGA) after generating
learner profiles through registration process.
        </p>
        <p>
          Discrete Particle Swarm Optimization (PSO) was
employed by Wang and Tsai [
          <xref ref-type="bibr" rid="ref19">19</xref>
          ] to choose the material
suitable for a review course based on the material relevance
degree, difficulty level and the number of available learning
resources.
        </p>
        <p>Based on the related works analysis presented above, we
notice that the adaptation algorithms used to select a set of
LOs adapted to the profile/Context of the learner can be
classified into two main categories (see Fig. 1):</p>
      </sec>
    </sec>
    <sec id="sec-4">
      <title>Rule-based techniques:</title>
    </sec>
    <sec id="sec-5">
      <title>Algorithms-based techniques :</title>
      <p>Ontology combined with SWRL adaptation rules is the
most used Rule-based technique. Ontology helps in
improving adaptive learning by providing a suitable
vocabulary for learners to describe the course materials and
represent the learner’s belief, expectation and context being
used for the recommendation of LOs which are dependent on
the domain ontology [4].</p>
      <p>- Semantic Algorithms: based on Ontology modeling
and reasoning based on different types of algorithms
- Evolutionary computing Algorithms that includes
genetic algorithm (GA), Swarm optimization techniques
(PSO and ACO techniques).</p>
      <p>ALGORITHMS USED TO IMPLEMENT THE ADAPTATION BY</p>
      <p>LOS SELECTION
Semantic
Algorithm
Evolutionar
y Algorithm
Evolutionar
y Algorithm
Evolutionar
y Algorithm
Evolutionar
y Algorithm</p>
      <p>Ontology - Semantic
search (Query expension
Ontology
-contextfiltering based regular
expression + Ontology
matching
GA - Compatible
Genetic Algorithm
(CGA)
ACO - attribute-based
ant colony system
(AACS)
GA - Variable lentgh
genetic algo
PSO for selecting LO</p>
      <p>Learning style,
teaching methods,
learning activities
Location-TimeProfile
Learning style
Knowledge level
Feedback
Learning
styleKnowledge level
Learning Style –
Knowledge level –
Goal
Difficultly level,
relevance of material</p>
      <sec id="sec-5-1">
        <title>B. Adaptation of LOs sequencing (Learning path adaptation):</title>
        <p>Curriculum sequencing, learning path adaptation,
adaptive learning path generation and adaptive learning
schema generation, designate all the same purpose, which is
the personalization and the adaptation of the learning
material sequence called learning path. Providing an optimal
learning path tailoring to the context of the learners is a
crucial issue in online learning adaptation. An optimal
learning path could reduce the student’s cognitive overload
and disorientation; consequently, this process would improve
the learner’s learning outcome and efficiency of the
adaptation in the online learning systems [5].</p>
        <p>This section presents a survey on learning path adaptation
efforts in the m/e learning environment from 2008 up to
2019. The survey highlights two points:

</p>
        <p>The different approaches to formulate the learning
path problem.</p>
        <p>The algorithms applied to solve the learning path
adaptation problem.</p>
      </sec>
      <sec id="sec-5-2">
        <title>1) Approaches (Problem formulation):</title>
        <p>
          The main objective in learning path adaptation is to
minimize the path or route of individual learning. According
to [
          <xref ref-type="bibr" rid="ref18">18</xref>
          ], to formulate the issue of learning path adaptation,
various approaches have emerged. Among these approaches:
 Constraints Satisfaction Problem (CSP): It’s a single
objective with several constraints. The problem in CSP
is defined as the state of the variable definition. The
solution space of the problem comprises all possible
sequences and the objective function is to minimize or
maximized the penalty function designed to evaluate
the sequencing [
          <xref ref-type="bibr" rid="ref10 ref11 ref12 ref13 ref14 ref15 ref16 ref17 ref18 ref19 ref20 ref9">5-20</xref>
          ]. Many works in the literature
proposed evolutionary algorithm, such as Genetic
Algorithm (GA) [
          <xref ref-type="bibr" rid="ref25 ref26">28-29</xref>
          ], Particle Swarm Optimization
(PSO) [
          <xref ref-type="bibr" rid="ref31">34</xref>
          ] or Ant Colony Optimization (ACO) [
          <xref ref-type="bibr" rid="ref29">32</xref>
          ]
and scheduling and planning Problem [
          <xref ref-type="bibr" rid="ref35">38</xref>
          ].
 Multi-Objective Optimization Problem (MOOP): The
concern in multi-objective optimization problem is to
satisfy multiple objectives simultaneously [5]. In
MOOP approach several algorithms are used, among
them GA[
          <xref ref-type="bibr" rid="ref22 ref23 ref24">25-27</xref>
          ], PSO[
          <xref ref-type="bibr" rid="ref32">35</xref>
          ], Heuristic algorithms
[2526] and Planning and Scheduling Technique [
          <xref ref-type="bibr" rid="ref36">39</xref>
          ].
 Domain modeling: This approach is implanted Through:
directed graph, concept map and ontology
[3-9-21-2211], however, there has been no formal model for
discussing learning path problems based on Domain
modeling [].
        </p>
      </sec>
      <sec id="sec-5-3">
        <title>2) Techniques:</title>
        <p>Once the learning path model has been formulated, the
methods to build the approach are chosen according to the
problem [5]. Table 2 presents the most used Algorithms in
the field of learning path adaptation.</p>
        <p>
          Reasoning based On ontology is present in several works
[3-9-21-22-11]. In such approach, reasoning techniques are
usually applied on metadata derived from an ontology model
[8]. The reasoning is performed in terms of SWRL (Semantic
Web Rule Language) rules that are applied on knowledge
represented in the OWL-DL (Description Logics) ontology.
Problem of concern with this approach is their
inappropriateness to reasoning with uncertainty. It should be
noted that some of the context elements are quantized with
uncertainty leading to certain ambiguity while defining and
reasoning with context, [8]. This problem can be dealt with
by integrating various reasoning models that may combine
probabilistic, Fuzzy reasoning techniques [8]. For that, we
highlight in this survey other works, which propose a hybrid
solution by combining Ontology-based reasoning with:
Fuzzy logic [
          <xref ref-type="bibr" rid="ref9">9</xref>
          ] and with a Greedy algo[
          <xref ref-type="bibr" rid="ref11">11</xref>
          ].
        </p>
        <p>
          Case based reasoning technique CBR as another
reasoning technique [
          <xref ref-type="bibr" rid="ref21">23-24</xref>
          ] is also used to implement the
learning path adaptation problem. CBR is the process of
solving new problems based on the solutions of similar past
problems. CBR has both the capacity to represent knowledge
and to reason about it. However, CBR suffers from the
inexistence of genericity in knowledge representation;
specific requirements for CBR are usually processed as they
come. There are also some limitations like as knowledge
acquisition problems for unavailable or limited cases,
Inference efficiency is not always good as desired, straight
forward provision of explanation is missing [5].
        </p>
        <p>
          Since Learning path problem is NP-Hard problem,
heuristic and meta-heuristics are usually used to approximate
its solutions. Heuristic search optimization algorithms are
used to implement a solution for the learning path adaptation;
among these algorithms we have Greedy algorithm and Hill
Clumbing algorithm. Greedy algorithm [
          <xref ref-type="bibr" rid="ref11 ref20 ref22">25, 20, 11</xref>
          ] is an
algorithmic paradigm that builds up a solution piece by
piece, always choosing the next piece that offers the most
obvious and immediate benefit. So the problem where
choosing locally optimal also leads to global solution are best
fit for Greedy. Hill Climbing algo [
          <xref ref-type="bibr" rid="ref23">26</xref>
          ], which is another
evolutionary Optimizer for optimal search, is used for
mathematical optimization problems in the field of Artificial
Intelligence. Given a large set of inputs and a good heuristic
function, it tries to find a sufficiently good solution to the
problem. This solution may not be the global optimal
maximum.
        </p>
        <p>
          According to [4], Meta-heuristic algorithms like
Evolutionary computation approaches (EC), have great
impact in the solution of the learning path adaptation
problem by providing appropriate learning paths to learners.
Genetic algorithms [25-27-28-29], Ant colony algorithms
[30-31-32-33] and Particle swarm optimization [
          <xref ref-type="bibr" rid="ref31 ref32">34-35</xref>
          ] are
widely used techniques in the construction of learning path
sequence.
        </p>
        <p>
          Machine learning techniques are widely present in the
learning path adaptation field; Through the use of
Reinforcement learning (RL) and Bayesian Network (BN).
RL is an area of Machine Learning. It is about taking suitable
action to maximize reward in a particular situation. It is
employed to find the best possible behavior or path it should
take in a specific situation. In the field of adaptive learning,
RL is used in [
          <xref ref-type="bibr" rid="ref33">36</xref>
          ]. The proposed approach consists of the
following steps. Firstly, the learner’s state is determined.
Secondly, a learning material or path is suggested through a
set of actions. Thirdly, based on RL, the learner state is
updated, in addition, the rewards received by recommended
learning paths or materials are updated.
        </p>
        <p>
          Bayesian Network BN (also known as Bayesian
probability theory) is also used for finding the adaptive
learning path [
          <xref ref-type="bibr" rid="ref34">37</xref>
          ]. BN is a directed graph whose nodes
represent the uncertain variables of interest and edges are
influential links between the variables. Node probability
table contains conditional probability (CP) values which are
assigned on the basis of the level of expertise, learning style
and learning pace of the learner. In the second step, BN is
constructed to calculate CP value for each knowledge unit in
the learning path. Finally, the shortest path is selected to
provide appropriate learning path for the learner [4].
        </p>
        <p>Planning&amp; scheduling techniques [38-39-40], as an
Artificial intelligence (AI) techniques, are also proposed to
generate sequences of e-learning routes which are tailored to
the students’ profiles.</p>
        <p>
          Employing Data mining (DM) in intelligent learning
systems has become a trend in developing learning systems,
which makes educational data mining the focus of a new and
growing research community. Such a technique has the
following strengths: (1) it reduces the constraints on the scale
of the database quality and the variable types; (2) it can
analyze both a continuous variable and discontinuous
variables efficiently; and (3) its results with graphical or rule
expressions can be understood easily and can be explained.
Lin in [
          <xref ref-type="bibr" rid="ref38">41</xref>
          ] suggested that learning materials based on the
tree mechanism can meet individual requirements and can
enhance learning efficiency in a learning environment.
        </p>
        <p>
          Other algorithms derived from the graph theory approach
are used for the same purpose, among these algorithms we
can mention: the first-search depth (DFS) [
          <xref ref-type="bibr" rid="ref39">42</xref>
          ], binary integer
programming and Adaptive Shortest path algorithm [44]
(See Fig. 2).
Evolutionary
Computing
Evolutionary
Computing
Machine
learning
Machine
learning
Planning &amp;
Scheduling
Planning &amp;
Scheduling
Planning &amp;
Scheduling
Graph based
Graph based
GA
GA
RL
        </p>
        <p>BN
Case based
planning
Planning
technique +
ontology +</p>
        <p>Intelligent
agents (Hybrid</p>
        <p>technique)
AI Planning and
scheduling
technique</p>
        <p>Adaptive
Shortest path</p>
        <p>algo
the depth
Firstsearch (DFS)</p>
        <p>Context model (Learner
motivation)
Knolwledge level,
Knowledge level,
Concept, learning
objective, Time
Context model
(environmental context,
social, cognitive,
Feedback)
preferences
Learner model
Learner model
Knowledge level,
Metadata LO, learning
style, learning objective
Time
Learning objective,
Learning background,
Preferences
Prior knowledge,
learning style
Previous knowledge,
time restriction</p>
      </sec>
    </sec>
    <sec id="sec-6">
      <title>IV. SUMMARY AND CONCLUSION</title>
      <p>Learning adaptation and personalization is an important
research field in e/m-learning environment. It is quite
necessary to discover the most efficient approach to realize
it. This paper presents a literature review of personalized and
adaptive learning algorithms from the two sides of
adaptation: the adaptation of the LOs selection and the
adaptation of the learning path or the LOs sequencing.</p>
      <p>Through the statistical analysis of the current
individualized learning algorithms, the different approaches
that are applied to construct them vary between semantic
algorithms based on the ontology modeling of the domain
model and the learner’s context model and evolutionary
computing techniques that includes genetic algorithms and
swarm optimization techniques. An additional set of
algorithms are used for the purpose of the learning path
adaptation, in this category we can find machine
learningbased algorithms like BN and RL, graph-based algorithms
and planning and scheduling techniques.</p>
      <p>In future work we will focus on the adaptation within
mLearning environment, which offer adapted learning
services in mobility, according to the nature of this kind of
learning systems, we need to integrate on the one hand more
learners contextual data like, location, time, mobility state,
device characteristics, environment characteristics…and in
the other hand information that characterizes the learning
task like learner’s Learning style, knowledge level,
preferences,… As adaptation type, we are interested in the
well-known learning path adaptation problem which plays a
central role in intelligent learning systems and it is
considered as one of the most challenging problems. Since
this problem is seen as a combinatorial optimization
problem, we are going to study the effects of the application
of computational evolutionary algorithms, which is still a
hot research field.</p>
      <p>Technology
(pp.</p>
    </sec>
  </body>
  <back>
    <ref-list>
      <ref id="ref1">
        <mixed-citation>
          <string-name>
            <surname>K.R. Premlatha</surname>
            ,
            <given-names>T.</given-names>
          </string-name>
          <article-title>V Geetha, “Learning content design and learner adaptation for adaptive e-learning environment: a survey”</article-title>
          ,
          <source>Artificial Intelligence Review</source>
          ,
          <volume>44</volume>
          (
          <issue>4</issue>
          ), pp.
          <fpage>443</fpage>
          -
          <lpage>465</lpage>
          ,
          <year>2015</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref2">
        <mixed-citation>
          <string-name>
            <given-names>D. G.</given-names>
            <surname>Sampson</surname>
          </string-name>
          , P. Zervas, “
          <article-title>Context-aware adaptive and personalized mobile learning systems</article-title>
          .
          <source>In Ubiquitous and mobile learning in the digital age”</source>
          , pp.
          <fpage>3</fpage>
          -
          <lpage>17</lpage>
          . Springer, New York, NY,
          <year>2013</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref3">
        <mixed-citation>
          <string-name>
            <given-names>K.</given-names>
            <surname>Jetinai</surname>
          </string-name>
          , “
          <article-title>Rule-based reasoning for resource recommendation in personalized e-learning”</article-title>
          ,
          <source>In 2018 International Conference on Information and Computer Technologies (ICICT)</source>
          , pp.
          <fpage>150</fpage>
          -
          <lpage>154</lpage>
          , IEEE,
          <year>2018</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref4">
        <mixed-citation>
          <string-name>
            <given-names>A.</given-names>
            <surname>Khamparia</surname>
          </string-name>
          and
          <string-name>
            <given-names>B.</given-names>
            <surname>Pandey</surname>
          </string-name>
          ,
          <string-name>
            <surname>B.</surname>
          </string-name>
          ,
          <article-title>“Knowledge and intelligent computing methods in e-learning”</article-title>
          ,
          <source>International Journal of technology enhanced learning</source>
          ,
          <volume>7</volume>
          (
          <issue>3</issue>
          ), pp.
          <fpage>221</fpage>
          -
          <lpage>242</lpage>
          ,
          <year>2015</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref5">
        <mixed-citation>
          <string-name>
            <given-names>A.</given-names>
            <surname>Muhammad</surname>
          </string-name>
          ,
          <string-name>
            <given-names>Q.</given-names>
            <surname>Zhou</surname>
          </string-name>
          ,
          <string-name>
            <given-names>G.</given-names>
            <surname>Beydoun</surname>
          </string-name>
          ,
          <string-name>
            <given-names>D.</given-names>
            <surname>Xu</surname>
          </string-name>
          and
          <string-name>
            <given-names>J.</given-names>
            <surname>Shen</surname>
          </string-name>
          , “
          <article-title>Learning path adaptation in online learning systems”</article-title>
          ,
          <source>In 2016 IEEE 20th International Conference on Computer Supported Cooperative Work in Design (CSCWD)</source>
          , pp.
          <fpage>421</fpage>
          -
          <lpage>426</lpage>
          . IEEE.,
          <year>2016</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref6">
        <mixed-citation>
          <string-name>
            <given-names>S.</given-names>
            <surname>Ouf</surname>
          </string-name>
          ,
          <string-name>
            <given-names>M.A.</given-names>
            <surname>Ellatif</surname>
          </string-name>
          ,
          <string-name>
            <given-names>S.E.</given-names>
            <surname>Salama</surname>
          </string-name>
          , and
          <string-name>
            <given-names>Y.</given-names>
            <surname>Helmy</surname>
          </string-name>
          , “
          <article-title>A proposed paradigm for smart learning environment based on semantic web”</article-title>
          ,
          <source>Computers in Human Behavior</source>
          ,
          <volume>72</volume>
          , pp.
          <fpage>796</fpage>
          -
          <lpage>818</lpage>
          ,
          <year>2016</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref7">
        <mixed-citation>
          <string-name>
            <given-names>B.</given-names>
            <surname>Zhang</surname>
          </string-name>
          ,
          <string-name>
            <given-names>C.</given-names>
            <surname>Yin</surname>
          </string-name>
          ,
          <string-name>
            <given-names>B.</given-names>
            <surname>David</surname>
          </string-name>
          ,
          <string-name>
            <given-names>Z.</given-names>
            <surname>Xiong</surname>
          </string-name>
          and
          <string-name>
            <given-names>W.</given-names>
            <surname>Niu</surname>
          </string-name>
          , “
          <article-title>Facilitating professionals' work-based learning with context-aware mobile system”</article-title>
          ,
          <source>Science of Computer Programming</source>
          ,
          <volume>129</volume>
          , pp.
          <fpage>3</fpage>
          -
          <lpage>19</lpage>
          ,
          <year>2016</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref8">
        <mixed-citation>
          <string-name>
            <given-names>R.</given-names>
            <surname>Benlamri</surname>
          </string-name>
          and
          <string-name>
            <given-names>X.</given-names>
            <surname>Zhang</surname>
          </string-name>
          , “
          <article-title>Context-aware recommender for mobile learners”</article-title>
          ,
          <source>Human-centric Computing and Information Sciences</source>
          ,
          <volume>4</volume>
          (
          <issue>1</issue>
          ), p.
          <fpage>12</fpage>
          ,
          <year>2014</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref9">
        <mixed-citation>
          [9]
          <string-name>
            <given-names>B. Bouihi M.</given-names>
            <surname>Bahaj</surname>
          </string-name>
          , “
          <article-title>Ontology and Rule-Based Recommender System for E-learning Applications”</article-title>
          ,
          <source>International Journal of Emerging Technologies in Learning</source>
          ,
          <volume>14</volume>
          (
          <issue>15</issue>
          ),
          <year>2019</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref10">
        <mixed-citation>
          [10]
          <string-name>
            <given-names>M.</given-names>
            <surname>Abech</surname>
          </string-name>
          ,
          <string-name>
            <given-names>C.A.</given-names>
            <surname>Costa</surname>
          </string-name>
          ,
          <string-name>
            <given-names>J.L.</given-names>
            <surname>Barbosa</surname>
          </string-name>
          ,
          <string-name>
            <given-names>S.J.</given-names>
            <surname>Rigo</surname>
          </string-name>
          and
          <string-name>
            <given-names>R.</given-names>
            <surname>Rosa</surname>
          </string-name>
          <string-name>
            <surname>Righi</surname>
          </string-name>
          , “
          <article-title>A model for learning objects adaptation in light of mobile and contextaware computing”</article-title>
          ,
          <source>Personal and Ubiquitous Computing</source>
          ,
          <volume>20</volume>
          (
          <issue>2</issue>
          ), pp.
          <fpage>167</fpage>
          -
          <lpage>184</lpage>
          ,
          <year>2016</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref11">
        <mixed-citation>
          [11]
          <string-name>
            <given-names>F.</given-names>
            <surname>Soualah-Alila</surname>
          </string-name>
          ,
          <string-name>
            <given-names>C.</given-names>
            <surname>Nicolle</surname>
          </string-name>
          and
          <string-name>
            <given-names>F.</given-names>
            <surname>Mendes</surname>
          </string-name>
          , “
          <string-name>
            <surname>Context-Aware Adaptive System For M-Learning</surname>
            <given-names>Personalization</given-names>
          </string-name>
          ”,
          <year>2014</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref12">
        <mixed-citation>
          [12]
          <string-name>
            <given-names>L.</given-names>
            <surname>Erazo-Garzón</surname>
          </string-name>
          ,
          <string-name>
            <given-names>A.</given-names>
            <surname>Patiño</surname>
          </string-name>
          ,
          <string-name>
            <given-names>P.</given-names>
            <surname>Cedillo</surname>
          </string-name>
          and
          <string-name>
            <given-names>A.</given-names>
            <surname>Bermeo</surname>
          </string-name>
          , “
          <article-title>CALMS: A Context-Aware Learning Mobile System Based on Ontologies”</article-title>
          ,
          <source>In 2019 Sixth International Conference on eDemocracy &amp; eGovernment (ICEDEG)</source>
          , pp.
          <fpage>84</fpage>
          -
          <lpage>91</lpage>
          . IEEE,
          <year>2019</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref13">
        <mixed-citation>
          [13]
          <string-name>
            <surname>K.M. Fouad</surname>
            ,
            <given-names>M.A.</given-names>
          </string-name>
          <string-name>
            <surname>Nofal</surname>
            ,
            <given-names>H.M.</given-names>
          </string-name>
          <string-name>
            <surname>Harb</surname>
            and
            <given-names>N.M.</given-names>
          </string-name>
          <string-name>
            <surname>Nagdy</surname>
          </string-name>
          , “
          <article-title>Using semantic web to support advanced web-based environment</article-title>
          ”,
          <year>2011</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref14">
        <mixed-citation>
          [14]
          <string-name>
            <given-names>E.</given-names>
            <surname>Kurilovas</surname>
          </string-name>
          ,
          <string-name>
            <given-names>S.</given-names>
            <surname>Kubilinskiene</surname>
          </string-name>
          and
          <string-name>
            <given-names>V.</given-names>
            <surname>Dagiene</surname>
          </string-name>
          , “
          <article-title>Web 3.0-Based personalisation of learning objects in virtual learning environments”</article-title>
          ,
          <source>Computers in Human Behavior</source>
          ,
          <volume>30</volume>
          , pp.
          <fpage>654</fpage>
          -
          <lpage>662</lpage>
          ,
          <year>2014</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref15">
        <mixed-citation>
          [15]
          <string-name>
            <surname>AZ. Sevkli</surname>
            ,
            <given-names>L.</given-names>
          </string-name>
          <string-name>
            <surname>Motiwalla</surname>
            and
            <given-names>H.F.</given-names>
          </string-name>
          <string-name>
            <surname>Abdulkarem</surname>
          </string-name>
          , “
          <article-title>The design and implementation of a context-aware mobile hadith learning system”</article-title>
          ,
          <source>International Journal of Mobile Learning and Organisation</source>
          ,
          <volume>11</volume>
          (
          <issue>4</issue>
          ), pp.
          <fpage>295</fpage>
          -
          <lpage>313</lpage>
          ,
          <year>2017</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref16">
        <mixed-citation>
          [16]
          <string-name>
            <given-names>B.C.L.</given-names>
            <surname>Christudas</surname>
          </string-name>
          ,
          <string-name>
            <given-names>E.</given-names>
            <surname>Kirubakaran</surname>
          </string-name>
          and
          <string-name>
            <given-names>P.R.J.</given-names>
            <surname>Thangaiah</surname>
          </string-name>
          , “
          <article-title>An evolutionary approach for personalization of content delivery in elearning systems based on learner behavior forcing compatibility of learning materials”</article-title>
          ,
          <source>Telematics and Informatics</source>
          ,
          <volume>35</volume>
          (
          <issue>3</issue>
          ), pp.
          <fpage>520</fpage>
          -
          <lpage>533</lpage>
          ,
          <year>2018</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref17">
        <mixed-citation>
          [17]
          <string-name>
            <given-names>Y.J.</given-names>
            <surname>Yang</surname>
          </string-name>
          and
          <string-name>
            <given-names>C.</given-names>
            <surname>Wu</surname>
          </string-name>
          , “
          <article-title>An attribute-based ant colony system for adaptive learning object recommendation”</article-title>
          .
          <source>Expert Systems with Applications</source>
          ,
          <volume>36</volume>
          (
          <issue>2</issue>
          ), pp.
          <fpage>3034</fpage>
          -
          <lpage>3047</lpage>
          ,
          <year>2009</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref18">
        <mixed-citation>
          [18]
          <string-name>
            <given-names>P.</given-names>
            <surname>Dwivedi</surname>
          </string-name>
          ,
          <string-name>
            <given-names>V.</given-names>
            <surname>Kant</surname>
          </string-name>
          and
          <string-name>
            <surname>K.K. Bharadwaj</surname>
          </string-name>
          , “
          <article-title>Learning path recommendation based on modified variable length genetic algorithm”</article-title>
          ,
          <source>Education and Information Technologies</source>
          ,
          <volume>23</volume>
          (
          <issue>2</issue>
          ), pp.
          <fpage>819</fpage>
          -
          <lpage>836</lpage>
          ,
          <year>2018</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref19">
        <mixed-citation>
          [19]
          <string-name>
            <given-names>T.I.</given-names>
            <surname>Wang</surname>
          </string-name>
          and
          <string-name>
            <given-names>K.H.</given-names>
            <surname>Tsai</surname>
          </string-name>
          , “
          <article-title>Interactive and dynamic review course composition system utilizing contextual semantic expansion and discrete particle swarm optimization”</article-title>
          ,
          <source>Expert Systems with Applications</source>
          ,
          <volume>36</volume>
          (
          <issue>6</issue>
          ), pp.
          <fpage>9663</fpage>
          -
          <lpage>9673</lpage>
          ,
          <year>2009</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref20">
        <mixed-citation>
          [20]
          <string-name>
            <given-names>P.</given-names>
            <surname>Basu</surname>
          </string-name>
          ,
          <string-name>
            <given-names>S.</given-names>
            <surname>Bhattacharya</surname>
          </string-name>
          and
          <string-name>
            <given-names>S.</given-names>
            <surname>Roy</surname>
          </string-name>
          , “February.
          <article-title>Online recommendation of learning path for an e-learner under virtual university”</article-title>
          ,
          <source>In International Conference on Distributed Computing and Internet Heidelberg</source>
          ,
          <year>2013</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref21">
        <mixed-citation>
          [24]
          <string-name>
            <given-names>D.</given-names>
            <surname>Mansouri</surname>
          </string-name>
          ,
          <string-name>
            <given-names>A.</given-names>
            <surname>Mille</surname>
          </string-name>
          and
          <string-name>
            <given-names>A.</given-names>
            <surname>Hamdi-Cherif</surname>
          </string-name>
          , “
          <article-title>Adaptive delivery of trainings using ontologies and case-based reasoning”</article-title>
          ,
          <source>Arabian Journal for Science and Engineering</source>
          ,
          <volume>39</volume>
          (
          <issue>3</issue>
          ), pp.
          <fpage>1849</fpage>
          -
          <lpage>1861</lpage>
          ,
          <year>2014</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref22">
        <mixed-citation>
          [25]
          <string-name>
            <given-names>G.</given-names>
            <surname>Durand</surname>
          </string-name>
          ,
          <string-name>
            <given-names>N.</given-names>
            <surname>Belacel</surname>
          </string-name>
          and
          <string-name>
            <given-names>F.</given-names>
            <surname>LaPlante</surname>
          </string-name>
          , “
          <article-title>Graph theory based model for learning path recommendation”</article-title>
          ,
          <source>Information Sciences, 251</source>
          , pp.
          <fpage>10</fpage>
          -
          <lpage>21</lpage>
          ,
          <year>2013</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref23">
        <mixed-citation>
          [26]
          <string-name>
            <given-names>V.</given-names>
            <surname>Tam</surname>
          </string-name>
          ,
          <string-name>
            <given-names>E.Y.</given-names>
            <surname>Lam</surname>
          </string-name>
          and
          <string-name>
            <given-names>S.T.</given-names>
            <surname>Fung</surname>
          </string-name>
          , “
          <article-title>A new framework of concept clustering and learning path optimization to develop the nextgeneration e-learning systems”</article-title>
          ,
          <source>journal of computers in education</source>
          ,
          <volume>1</volume>
          (
          <issue>4</issue>
          ), pp.
          <fpage>335</fpage>
          -
          <lpage>352</lpage>
          ,
          <year>2014</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref24">
        <mixed-citation>
          [27]
          <string-name>
            <given-names>N.C.</given-names>
            <surname>Benabdellah</surname>
          </string-name>
          ,
          <string-name>
            <given-names>M.</given-names>
            <surname>Gharbi</surname>
          </string-name>
          and
          <string-name>
            <given-names>M.</given-names>
            <surname>Bellafkih</surname>
          </string-name>
          , “Units'
          <article-title>Categorization Model: The Adapted Genetic Algorithm for a Personalized E-Content”</article-title>
          ,
          <source>In Europe and MENA Cooperation Advances in Information and Communication Technologies</source>
          (pp.
          <fpage>149</fpage>
          -
          <lpage>158</lpage>
          ). Springer, Cham,
          <year>2017</year>
          ..
        </mixed-citation>
      </ref>
      <ref id="ref25">
        <mixed-citation>
          [28]
          <string-name>
            <given-names>T.Y.</given-names>
            <surname>Chang</surname>
          </string-name>
          and
          <string-name>
            <given-names>Y.R.</given-names>
            <surname>Ke</surname>
          </string-name>
          , “
          <article-title>A personalized e-course composition based on a genetic algorithm with forcing legality in an adaptive learning system</article-title>
          .
          <source>Journal of Network and Computer Applications</source>
          ,
          <volume>36</volume>
          (
          <issue>1</issue>
          ), pp.
          <fpage>533</fpage>
          -
          <lpage>542</lpage>
          ,
          <year>2013</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref26">
        <mixed-citation>
          [29]
          <string-name>
            <given-names>I. El</given-names>
            <surname>Guabassi</surname>
          </string-name>
          ,
          <string-name>
            <given-names>M. Al</given-names>
            <surname>Achhab</surname>
          </string-name>
          ,
          <string-name>
            <given-names>I.</given-names>
            <surname>Jellouli</surname>
          </string-name>
          and
          <string-name>
            <given-names>B.E.E.</given-names>
            <surname>Mohajir</surname>
          </string-name>
          , “
          <article-title>Personalized Ubiquitous Learning via an Adaptive Engine</article-title>
          .”,
          <source>International Journal of Emerging Technologies in Learning (iJET)</source>
          ,
          <volume>13</volume>
          (
          <issue>12</issue>
          ), pp.
          <fpage>177</fpage>
          -
          <lpage>190</lpage>
          ,
          <year>2018</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref27">
        <mixed-citation>
          [30]
          <string-name>
            <given-names>N.</given-names>
            <surname>Benabdellah</surname>
          </string-name>
          ,
          <string-name>
            <given-names>M.</given-names>
            <surname>Gharbi</surname>
          </string-name>
          and
          <string-name>
            <given-names>M.</given-names>
            <surname>Bellafkih</surname>
          </string-name>
          , “
          <string-name>
            <surname>Toward E-Content</surname>
            <given-names>Adaptation</given-names>
          </string-name>
          :
          <article-title>Units' Sequence and Adapted Ant Colony Algorithm</article-title>
          .,” Information,
          <volume>6</volume>
          (
          <issue>3</issue>
          ), pp.
          <fpage>564</fpage>
          -
          <lpage>575</lpage>
          ,
          <year>2015</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref28">
        <mixed-citation>
          [31]
          <string-name>
            <given-names>A.P.</given-names>
            <surname>Dharshini</surname>
          </string-name>
          ,
          <string-name>
            <given-names>S.</given-names>
            <surname>Chandrakumarmangalam</surname>
          </string-name>
          and G. Arthi, “
          <article-title>Ant colony optimization for competency based learning objects sequencing in e-learning,”</article-title>
          <source>Applied Mathematics and Computation</source>
          ,
          <volume>263</volume>
          , pp.
          <fpage>332</fpage>
          -
          <lpage>341</lpage>
          ,
          <year>2015</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref29">
        <mixed-citation>
          [32]
          <string-name>
            <given-names>S.</given-names>
            <surname>Sengupta</surname>
          </string-name>
          ,
          <string-name>
            <given-names>S.</given-names>
            <surname>Sahu</surname>
          </string-name>
          and
          <string-name>
            <given-names>R.</given-names>
            <surname>Dasgupta</surname>
          </string-name>
          , “
          <article-title>Construction of learning path using ant colony optimization from a frequent pattern graph,”</article-title>
          ,
          <source>arXiv preprint arXiv:1201.3976</source>
          ,
          <year>2012</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref30">
        <mixed-citation>
          [33]
          <string-name>
            <surname>L. de Marcos</surname>
            ,
            <given-names>J.J.</given-names>
          </string-name>
          <string-name>
            <surname>Martínez</surname>
            and
            <given-names>J.A.</given-names>
          </string-name>
          <string-name>
            <surname>Gutiérrez</surname>
          </string-name>
          ,”
          <article-title>Swarm intelligence in e-learning: a learning object sequencing agent based on competencies”</article-title>
          ,
          <source>In Proceedings of the 10th annual conference on Genetic and evolutionary computation</source>
          (pp.
          <fpage>17</fpage>
          -
          <lpage>24</lpage>
          ). ACM,
          <year>2008</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref31">
        <mixed-citation>
          [34]
          <string-name>
            <given-names>C.P.</given-names>
            <surname>Chu</surname>
          </string-name>
          ,
          <string-name>
            <given-names>Y.C.</given-names>
            <surname>Chang</surname>
          </string-name>
          and
          <string-name>
            <given-names>C.C.</given-names>
            <surname>Tsai</surname>
          </string-name>
          , “
          <article-title>PC 2 PSO: personalized ecourse composition based on Particle Swarm Optimization”</article-title>
          ,
          <source>Applied Intelligence</source>
          ,
          <volume>34</volume>
          (
          <issue>1</issue>
          ), pp.
          <fpage>141</fpage>
          -
          <lpage>154</lpage>
          ,
          <year>2011</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref32">
        <mixed-citation>
          [35]
          <string-name>
            <given-names>D.</given-names>
            <surname>Shawky</surname>
          </string-name>
          and
          <string-name>
            <given-names>A.</given-names>
            <surname>Badawi</surname>
          </string-name>
          , “
          <string-name>
            <surname>February</surname>
          </string-name>
          .
          <article-title>A reinforcement learningbased adaptive learning system”</article-title>
          ,
          <source>In International Conference on Advanced Machine Learning Technologies and Applications</source>
          (pp.
          <fpage>221</fpage>
          -
          <lpage>231</lpage>
          ). Springer, Cham,
          <year>2018</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref33">
        <mixed-citation>
          [36]
          <string-name>
            <given-names>N.V.</given-names>
            <surname>Anh</surname>
          </string-name>
          ,
          <string-name>
            <surname>N.V.</surname>
          </string-name>
          , Ha and
          <string-name>
            <given-names>H.S.</given-names>
            <surname>Dam</surname>
          </string-name>
          , “
          <article-title>Constructing a Bayesian belief network to generate learning path in adaptive hypermedia system</article-title>
          ”
          <source>Journal of Computer Science and Cybernetics</source>
          ,
          <volume>24</volume>
          (
          <issue>1</issue>
          ), pp.
          <fpage>12</fpage>
          -
          <lpage>19</lpage>
          ,
          <year>2008</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref34">
        <mixed-citation>
          [37]
          <string-name>
            <given-names>A.</given-names>
            <surname>Garrido</surname>
          </string-name>
          ,
          <string-name>
            <given-names>L.</given-names>
            <surname>Morales</surname>
          </string-name>
          and
          <string-name>
            <surname>I. Serina</surname>
          </string-name>
          , “
          <article-title>On the use of case-based planning for e-learning personalization”</article-title>
          ,
          <source>Expert Systems with Applications</source>
          ,
          <volume>60</volume>
          , pp.
          <fpage>1</fpage>
          -
          <lpage>15</lpage>
          ,
          <year>2016</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref35">
        <mixed-citation>
          [38]
          <string-name>
            <given-names>B.</given-names>
            <surname>Fernández-Reuter</surname>
          </string-name>
          ,
          <string-name>
            <given-names>E.</given-names>
            <surname>Durán</surname>
          </string-name>
          and
          <string-name>
            <given-names>A.</given-names>
            <surname>Amandi</surname>
          </string-name>
          , “
          <article-title>Designing a hybrid method for personalized ubiquitous learning paths generation”</article-title>
          ,
          <source>In 2017 36th International Conference of the Chilean Computer Science Society (SCCC)</source>
          (pp.
          <fpage>1</fpage>
          -
          <lpage>9</lpage>
          ). IEEE,
          <year>2017</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref36">
        <mixed-citation>
          [39]
          <string-name>
            <given-names>A.</given-names>
            <surname>Garrido</surname>
          </string-name>
          and E. Onaindia, “
          <article-title>Assembling learning objects for personalized learning: An AI planning perspective”</article-title>
          ,
          <source>IEEE Intelligent Systems</source>
          ,
          <volume>28</volume>
          (
          <issue>2</issue>
          ), pp.
          <fpage>64</fpage>
          -
          <lpage>73</lpage>
          ,
          <year>2011</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref37">
        <mixed-citation>
          [40]
          <string-name>
            <given-names>C.F.</given-names>
            <surname>Lin</surname>
          </string-name>
          ,
          <string-name>
            <given-names>Y.C.</given-names>
            <surname>Yeh</surname>
          </string-name>
          ,
          <string-name>
            <given-names>Y.H.</given-names>
            <surname>Hung</surname>
          </string-name>
          and
          <string-name>
            <surname>R.I. Chang</surname>
          </string-name>
          , “
          <article-title>Data mining for providing a personalized learning path in creativity: An application of decision trees”</article-title>
          ,
          <source>Computers &amp; Education</source>
          , 68, pp.
          <fpage>199</fpage>
          -
          <lpage>210</lpage>
          ,
          <year>2013</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref38">
        <mixed-citation>
          [41]
          <string-name>
            <given-names>A.H.</given-names>
            <surname>Nabizadeh</surname>
          </string-name>
          ,
          <string-name>
            <given-names>A. Mário</given-names>
            <surname>Jorge</surname>
          </string-name>
          and
          <string-name>
            <given-names>J. Paulo</given-names>
            <surname>Leal</surname>
          </string-name>
          , “
          <string-name>
            <surname>July</surname>
          </string-name>
          . Rutico:
          <article-title>Recommending successful learning paths under time constraints”</article-title>
          ,
          <source>In Adjunct Publication of the 25th Conference on User Modeling, Adaptation and Personalization</source>
          (pp.
          <fpage>153</fpage>
          -
          <lpage>158</lpage>
          ). ACM,
          <year>2017</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref39">
        <mixed-citation>
          [42]
          <string-name>
            <given-names>N.</given-names>
            <surname>Belacel</surname>
          </string-name>
          ,
          <string-name>
            <given-names>G.</given-names>
            <surname>Durand</surname>
          </string-name>
          and
          <string-name>
            <given-names>F.</given-names>
            <surname>Laplante</surname>
          </string-name>
          , “
          <article-title>A Binary Integer Programming Model for Global Optimization of Learning Path Discovery”</article-title>
          .
          <source>In EDM (Workshops)</source>
          ,
          <year>2014</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref40">
        <mixed-citation>
          [43]
          <string-name>
            <given-names>I.A.</given-names>
            <surname>Alshalabi</surname>
          </string-name>
          ,
          <string-name>
            <given-names>S.E.</given-names>
            <surname>Hamada</surname>
          </string-name>
          ,
          <string-name>
            <given-names>K.</given-names>
            <surname>Elleithy</surname>
          </string-name>
          ,
          <string-name>
            <given-names>I.</given-names>
            <surname>Badara</surname>
          </string-name>
          and
          <string-name>
            <given-names>S.</given-names>
            <surname>Moslehpour</surname>
          </string-name>
          , “
          <article-title>Automated Adaptive Mobile Learning System using Shortest Path Algorithm and Learning Style”</article-title>
          ,
          <source>International Journal of Interactive Mobile Technologies</source>
          ,
          <volume>12</volume>
          (
          <issue>5</issue>
          ),
          <year>2018</year>
          .
        </mixed-citation>
      </ref>
    </ref-list>
  </back>
</article>