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<article xmlns:xlink="http://www.w3.org/1999/xlink">
  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>Reviews of Cultural Artefacts: Towards a Schema for their Annotation</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Kristin Kutzner</string-name>
          <email>kutznerk@uni-hildesheim.de</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Anna Moskvina</string-name>
          <email>moskvina@uni-hildesheim.de</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Kristina Petzold</string-name>
          <email>petzold@uni-hildesheim.de</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Claudia Roßkopf</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Ulrich Heid</string-name>
          <email>heidul@uni-hildesheim.de</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Ralf Knackstedt</string-name>
          <email>ralf.knackstedt@uni-hildesheim.de</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Institute for Business Administration and Business Information Systems, Institute for Information Science and Language Technologies, Institute for Creative Writing and Literary Studies, Institute for Cultural Politics University of Hildesheim</institution>
          ,
          <addr-line>Universitätsplatz 1, 31141 Hildesheim</addr-line>
          ,
          <country country="DE">Germany</country>
        </aff>
      </contrib-group>
      <fpage>17</fpage>
      <lpage>23</lpage>
      <abstract>
        <p>Digital transformation allows new forms of discussion on cultural and aesthetic practices. Several stakeholders are able to comment and discuss cultural artefacts (books, museums and their exhibitions). Today, a variety of platforms exists: from general platforms (e.g., Amazon, Tripadvisor) to specialized ones (e.g., LovelyBooks, Behance). So far, there has not been any analysis of reviews of cultural artefacts across platforms. Accordingly, this study identifies and classifies text components of reviews about cultural artefacts. Based on the coding paradigm in the sense of Grounded Theory, (1) the components are empirically identified and (2) structured, resulting in a first category system. After evaluating and modifying the system (3), a multi-layered category system resulted. Thereafter, a group of students applied the system to provide insights into the understandability of the system. By providing such a categorisation, we intend to contribute to further research in analysing the contents and text structure of online reviews.</p>
      </abstract>
      <kwd-group>
        <kwd>cultural artefacts</kwd>
        <kwd>reviews</kwd>
        <kwd>multi-layered category system</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>-</title>
      <p>
        Today, a variety of online platforms including
ecommerce, social media and specialized rating platforms,
allows consumers to rate and communicate their opinion
about products or services. According to industry research
reports, purchasing decisions of consumers are highly
influenced by online reviews
        <xref ref-type="bibr" rid="ref5 ref6">(Deloitte, 2007; Duan et al.,
2008)</xref>
        . Further, a
        <xref ref-type="bibr" rid="ref23">Nielsen (2012)</xref>
        report, surveying more
than 28.000 internet users worldwide, found that such
online customer reviews are the second most trusted source
of brand information.
      </p>
      <p>
        Furthermore, digital transformation supports new or
changed forms of collaboration
        <xref ref-type="bibr" rid="ref17">(Kutzner et al., 2018)</xref>
        and
participation
        <xref ref-type="bibr" rid="ref24 ref25">(O’Reilly, 2005)</xref>
        , including discussion on
cultural and aesthetic practices. Through the interactive
mode of digital media for instance the formerly clear lines
between different groups of stakeholders are blurring, e.g.
between producer and consumer
        <xref ref-type="bibr" rid="ref34">(see the notion of
‘Prosumer’ in Toffler, 1980)</xref>
        and between laymen and
professionals. Nearly every cultural artefact can get a
review: a movie (e.g., imdb.com), a book (e.g.,
goodreads.com) or a new mobile application. In this study
we focus on artistic artefacts (museums and their
exhibitions) and books as cultural artefacts. Writing a
review about such an artefact, a reviewer can choose
among a variety of platforms, from general, commercial
platforms (e.g., Amazon, Tripadvisor) and specialized
platforms and community-based platforms (e.g.,
LovelyBooks, Behance) to more text oriented platforms
(e.g., Sobooks, Mojoreads, Lectory). Some of these
platforms not only present the related cultural artefacts, but
also support the interaction between several reviewers
(comments function), the rating of cultural artefacts and its
participative further development (co-creation). In this
field, reviews about cultural artefacts can be seen as textual
materializations of cultural practices and of their
perception.
      </p>
      <p>Earlier studies have tended to address heterogeneous and
mostly isolated aspects concerning reviews. Most of them
analysed reviews in English. For instance, based on product
ratings, e-commerce platforms, especially Amazon (e.g.,</p>
      <p>
        McAuley and Leskovec, 2013), analysed online consumer
reviews. A few studies analysed reviews in German
        <xref ref-type="bibr" rid="ref22">(e.g.,
Mehling et al., 2018)</xref>
        . Computational and linguistic
processing focused on techniques like opinion mining
        <xref ref-type="bibr" rid="ref26">(e.g.,
Pang and Lee, 2008)</xref>
        or sentiment analysis
        <xref ref-type="bibr" rid="ref15 ref35">(e.g, Wiegand
and Ruppenhofer, 2015; Klinger et al., 2016)</xref>
        to investigate
how reviews can be automatically classified into being
positive, negative or neutral. However, to the best of our
knowledge, there is no research approach analysing
reviews, especially about cultural artefacts, across
platforms. Therefore, this study focuses on reviews of
cultural artefacts (books, museums and their exhibitions) in
German from different types of platforms. Accordingly, we
aim to answer the following research question as a basis for
further research:

      </p>
      <p>What kind of components are contained in reviews
of cultural artefacts?
Our contribution is a multi-layered category system for
characterising components of reviews of cultural artefacts
(e.g., contents and communicative acts). The category
system contributes to our ongoing research on reviews in
the digital world and aims at characterising and analysing
reviews of cultural artefacts. Therefore, as a next step after
building the category system, we hope to be able to find
patterns of components within reviews. In a first step, we
briefly outline the background of reviews, cultural artefacts
and the digital world in which they are written (Section 2).
Based on our research design (Section 3), we iteratively
built the multi-layered category system (Section 4) and
evaluated it, applying it several times (Section 5). We then
discuss the results and future research directions (Section
6) and conclude with our main findings (Section 7).
2.</p>
    </sec>
    <sec id="sec-2">
      <title>Background</title>
      <p>In this section, we specify the terms related to our research
question. Therefore, we introduce our definition of a
cultural artefact, the concept of a review and its
components.</p>
      <p>In this study, we define cultural artefacts as artistic artefacts
(museums and their exhibitions) and books. This focus on
the cultural field also defines the sort of review we are
looking for. In this context the concept of a review is
characterized by its strong relation to the tradition of art and
literary criticism as a professional journalistic form of
discussing and reviewing newly published cultural
artefacts.</p>
      <p>In general, scholars and practitioners do not agree on a
universal definition of the term review and of its
components. Therefore, a review could be analysed and
understood from different point of views. Some of the most
prominent positions include the following statements:



</p>
      <p>
        Review as a product of evaluation of a cultural
artefact: a review is considered as an article published
by a journalist, that describes, explains, interprets
and/or evaluates a cultural artefact. Most
characteristic parts of a review include
recommendation or dissuasion as well as statements
on the originality and entertaining qualities of an
artefact
        <xref ref-type="bibr" rid="ref31">(Stegert, 1997)</xref>
        .
      </p>
      <p>
        Review as the central text type of literary criticism: a
review is understood as the critical discussion of a
new publication; the most common and most
important type of text in literary criticism
        <xref ref-type="bibr" rid="ref25">(Pfohlmann, 2005)</xref>
        .
      </p>
      <p>
        Review as an expert expression of opinion: a review
is the opinion-expressing form of literary and art
criticism. Book reviews, film criticism, a judgmental
report on a painting exhibition or an expert
journalistic expression are examples
        <xref ref-type="bibr" rid="ref18">(La Roche et al.,
2013)</xref>
        .
      </p>
      <p>
        Review means asking for terms of arts, their
functions and their origin. It further involves judging,
making oneself unpopular and not being afraid of
misunderstandings
        <xref ref-type="bibr" rid="ref29">(Rauterberg, 2007)</xref>
        .
      </p>
      <p>As the statements indicate, a review may contain several
components, addressing several aspects of a cultural
artefact. For instance, descriptions, explanations,
interpretations of an artefact as well as its critical
discussion and expressions of the reviewer’s opinion are
components of a review. Consequently, a review is
characterised by several textual components and, therefore,
can be analysed from different perspectives. Furthermore,
reviews and their components might vary depending on the
type of platform (e.g., general platforms like Amazon and
Tripadvisor, specialized and community-based platforms
like LovelyBooks or Behance) and on the addressed
cultural artefact (e.g., books, museums and their
exhibitions). However, existing research mostly tended to
address isolated aspects of reviews. Therefore, there still
seems to be a need to investigate multiple perspectives on
reviews of cultural artefacts. Accordingly, in this study we
aim to provide a multi-layered category system that covers
several perspectives on a review, as a basis for further
research in this field.</p>
    </sec>
    <sec id="sec-3">
      <title>Research Design</title>
      <p>
        In order to identify components of reviews we conducted
an iterative three-stage research design, containing build
and evaluate activities that characterise the Design Science
Research in Information Systems
        <xref ref-type="bibr" rid="ref19 ref27 ref4">(e.g., March and Smith,
1995; Peffers et al., 2007)</xref>
        . It consists of (Stage 1) the
identification of components and (Stage 2) the
development of a category system (build activities). To
leverage rigorousness and to demonstrate the utility,
quality and efficacy of the category system, we evaluated
the system (Stage 3, evaluate activities), applying it several
times (Figure 1).
      </p>
      <p>d
il
u
B
e
t
a
u
l
a
v
E</p>
      <p>Stage 1:</p>
      <p>Identify
components</p>
      <p>Stage 2:
Develop
category
system
Stage 3:
Evaluate
category
system</p>
      <p>Inputs</p>
      <p>Methods/Steps</p>
      <p>Outputs
• Sample reviews
• 130 types of
review
components
• Sample reviews
• Multi-layered
category system
• Perform open
coding
iteratively
• Perform axial
coding
iteratively
• Apply
multilayered
category system
iteratively
• 130 types of
review
components
• Multi-layered
category system
• Adapted
multilayered
category system
As a compact guideline for annotators, we built a tabular
overview that complements the hierarchically ordered,
labelled components by operationalised explanations and
examples (codebook).</p>
      <p>Presentation of selected categories. As described above,
each layer consists of several hierarchically ordered
categories. In total, the category system contains 108
different categories. More than half of the categories are
assigned to Layer 1. On the topmost level, Layer 1 contains
eight categories (Figure 3). For reasons of space
limitations, we will only present selected subcategories of
category 1.1 in more detail (Figure 4).</p>
      <p>Layer 1—Content
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8</p>
      <sec id="sec-3-1">
        <title>Reviewer-Artefact-Relation: Focused</title>
      </sec>
      <sec id="sec-3-2">
        <title>Reviewer-Artefact-Relation: Extended</title>
      </sec>
      <sec id="sec-3-3">
        <title>Artefact-Author-Relation and its Environment Artefact in Medium 1-Artefact in Medium 2-Relation (Intermediality of the Artefacts)</title>
      </sec>
      <sec id="sec-3-4">
        <title>Relation between Artefacts</title>
      </sec>
      <sec id="sec-3-5">
        <title>Reflexions on the Review(ing Process)</title>
      </sec>
      <sec id="sec-3-6">
        <title>Reviewers’ Self-thematisation</title>
      </sec>
      <sec id="sec-3-7">
        <title>Relation between Reviews</title>
        <p>
          have been independently analysed by three students.
Subsequently, we measured the nominal scale agreement
          <xref ref-type="bibr" rid="ref8 ref9">(Fleiss kappa, e.g., Fleiss, 1971; Fleiss and Cohen, 1973)</xref>
          and the absolute observed agreement of each category, to
measure the agreement between the three raters. We further
asked the students for their experience which categories
they found easier to identify than others.
        </p>
      </sec>
    </sec>
    <sec id="sec-4">
      <title>Category System of Review Components</title>
      <p>Following the research design (Section 3), we built a
multilayered category system, containing multiple components
of a review (Stage 1 and 2). In this section, we describe the
category system in general and, for reasons of space
limitations, we only present selected components of Layer
1 and 2 in more detail.
 1 …</p>
      <p>a
…
1.1

1.
Layer 1—Content
Layer 2—General Criticism
Layer 3—Style
Layer 4—Further Information</p>
      <p>The category system is used to annotate text strings in the
reviews. Further, the categories are organized in a
hierarchical structure, where each category has a numerical
and a textual label used in the practical annotation work.
For instance, Layer 1 contains category  1 that is divided
into several subcategories from  1.1 to  1. . A
subcategory can be divided into further subcategories and
so on (Figure 2).</p>
      <sec id="sec-4-1">
        <title>Ambivalent …</title>
        <p>Layer 1—Category 1.1. This category contains various
themes addressed by the reviewers that are directly related
to the cultural artefact. First, the reviewer might discuss
individual aspects (category 1.1.1) related to the artefact.
For instance, he or she might quote some content, address
the translation, the author, detailed content or the title of the
artefact. Also physical properties such as the quality of
paper or illustrations, the outer appearance of the reviewed
book (e.g., cover or used condition) and the language style
of the artefact can be addressed by the reviewer.
Alternatively or in addition, not only individual aspects, but
also the artefact as a whole can be discussed (Figure 4).
Layer 2—Category 2. Addressing the categories of Layer
1, the reviewer always pursues some intention. Therefore,
Layer 2 offers different communicative acts in the reviews
for annotating these intentions (Figure 4).</p>
        <p>5.</p>
      </sec>
    </sec>
    <sec id="sec-5">
      <title>Application and Evaluation</title>
      <p>As a first test of the category system, 24 students were
asked to apply it in the manual annotation of 430 randomly
selected Amazon reviews (Stage 3 of the research design).
We now present an example of an annotated text passage
which illustrates how labels from our category system are
attached to text components of a review. In addition, we
present selected results of the evaluation of the category
system.</p>
      <p>Annotation example. Annotators of reviews might
usefully read a given review several times, from different
perspectives. As a result, each text passage of the review is
annotated with categories of both, Layer 1 and 2. If it
involves a particular language style or multimedia content,
the categories of Layer 3 and 4 can be additionally
annotated.</p>
      <sec id="sec-5-1">
        <title>Original, German Text Passage Free Translation</title>
      </sec>
      <sec id="sec-5-2">
        <title>Ein sehr charmant witziges A very charming</title>
        <p>1.1.2, 2.10.1
1.1.2, 2.10.1
und unterhaltsames Buch
and entertaining book
ganz im typischen Stil
1.1.2, 2.10.1
1.1.1.8, 2.9</p>
      </sec>
      <sec id="sec-5-3">
        <title>Ellen DeGeneres.</title>
        <p>1.1.1.3, 2.9
1.2, 2.10.1
in the typical style of</p>
        <p>1.1.1.8, 2.9
Ellen DeGeneres.</p>
        <p>1.1.1.3, 2.9
mentioned by the reviewer (category 2.9). Third, the
annotator should take the perspectives of Layer 3 and 4.
However, as the sample text passage does not address these
categories, no further annotation is required (Figure 5).
Evaluation. Applying the category system and annotating
430 reviews, the students had to annotate sentences or
indicator expressions (such as those underlined in Figure 5)
with the labels from our category system. In sum, 14.235
text passages have been identified and annotated with
categories by the students. Some categories have been more
frequently used than others. For instance, the content of an
artefact (category 1.1.1.4) is most commonly recognized by
the students (2603 times). The summary of some content is
the second most common category (category 2.1) that is
recognized by the students (2403 times, Figure 6).</p>
      </sec>
      <sec id="sec-5-4">
        <title>Top 10— Frequencies of Categories (Total of 430 Reviews)</title>
      </sec>
      <sec id="sec-5-5">
        <title>View of the Artefact as a Whole</title>
      </sec>
      <sec id="sec-5-6">
        <title>Language Style</title>
      </sec>
      <sec id="sec-5-7">
        <title>Own Emotions</title>
      </sec>
      <sec id="sec-5-8">
        <title>Physical Properties of the Artefact Negative/Disagreement</title>
      </sec>
      <sec id="sec-5-9">
        <title>Mention without Assessment</title>
      </sec>
      <sec id="sec-5-10">
        <title>Outer Appearance</title>
        <p>For analysing the agreement between three raters regarding
each category, we reduced the data set to reviews that have
been annotated threefold (Triple), resulting in 139 reviews
and different overall frequency figures for the categories
(Figure 7).</p>
        <p>
          A calculation of the inter-annotator agreement on the task
is not trivial and yet provides only limited insight. On the
one hand, not all text passages have consistently been
annotated by all annotators at both levels (Layers 1 and 2);
this leads, for example, to low values of Fleiss’ kappa. On
the other hand, the category system contains a large number
of categories, and many of them have rarely been used, so
that the calculation does not provide adequately
interpretable results. As a consequence, we get rather low
kappa values
          <xref ref-type="bibr" rid="ref16">(the same applies for Krippendorff’s alpha for
most categories, Krippendorff, 2011)</xref>
          which at first sight
suggest little agreement between the annotators.
Nevertheless, we can interpret some of the data, calculating
the absolute agreement for each category. For instance,
regarding the most frequently used category, Content
(1.1.1.4), in 48% of the cases the raters use this category
unanimously. Furthermore, in 24% of the annotations, two
raters agree and one rater disagrees (i.e., he or she does not
use the category Content for annotating the same sentence).
Only in 28% of the cases, two raters disagree and one
agrees. Thus, in 72% of the cases the majority of the raters
agrees on the use of the category Content (Figure 8). As
described in Section 3, we also asked for the students’
personal opinion about accurately assignable (vs.
problematic) categories. The most commonly mentioned
category is category Content: this confirms the calculated
result. Thus, we can conclude that this category is
understandable for the raters and easy to identify in the
reviews. A similar interpretation applies to the use of
category 1.1.2 (view of the artefact as a whole). Regarding
the absolute agreement of this category, in 66% of the cases
only one rater uses category 1.1.2. In only 7% of the cases,
three raters agree on the use of this category (Figure 8). In
the student’s comments, category 1.1.2 is mentioned as not
accurately assignable by the majority. Thus, both results
indicate that category 1.1.2 is not understandable enough
and hard to identify in the review texts and thus has to be
improved.
        </p>
        <p>Relation of raters who agree
and disagree (agree : disagree)
No.
1.1.1.4
1.1.2</p>
        <p>Category
Content
View of the Artefact as a Whole
3:0
48%
7%</p>
      </sec>
    </sec>
    <sec id="sec-6">
      <title>Discussion and Future Research</title>
    </sec>
    <sec id="sec-7">
      <title>Directions</title>
      <p>As described in Section 5, the absolute observed agreement
per category provides first insights into the
comprehensibility of the categories. As a consequence, we
are able to revise the category system. From the first
annotation experiment we learn that positive evaluative
statements are much more frequent in our sample than
negative ones; many reviews make reference to the style or
language of the reviewed book; and the physical
appearance of the book is mentioned quite prominently,
likely because of the special situation of Amazon
delivering the book. Finally, we note that a considerable
number of annotated text passages make reference to the
emotions of the reviewers during the reception process.
However, because of several circumstances (e.g., variety of
incomplete annotations) the measurement of the nominal
scale agreement (Fleiss kappa) could not provide sufficient
results. As described above (Section 3), the category
system is meant to be platform-independent and generic
enough to be applicable to both, reviews of artistic artefacts
and books. Thus, the described evaluation can only be seen
as a partial evaluation activity in progress. The enhanced
category system will be applied, in more controlled
experiments, for reviews of artistic artefacts as well,
resulting in new annotations of reviews and additional
sample annotations to measure the agreement between
raters.</p>
      <p>
        Moreover, the category system represents an idealized
schema for annotating reviews. It serves as a starting point
to manually analyse the components of reviews. However,
as a next step, we want to identify the review components
automatically with methods of machine learning. For
instance, the use of support vector machines
        <xref ref-type="bibr" rid="ref1 ref19 ref4">(e.g., Cortes
and Vapnik 1995; Boser et al., 1992)</xref>
        or decision trees
        <xref ref-type="bibr" rid="ref28 ref3">(e.g.,
Rasoul and Landgrebe, 1991; Cho et al. 2002)</xref>
        can support
the automatic classification of the components. The
annotations that are manually identified by the students
(Section 3) and/or in new annotation rounds, may serve as
training data to learn a model and to predict components of
reviews.
      </p>
      <p>
        Furthermore, in the medium term, we not only want to
identify components of reviews, but also patterns of and
relationships between components (e.g., relationship
between the view of the artefact as a whole and its
assessment). Therefore, the training data can be used as an
input for further machine learning algorithms, like cluster
analysis
        <xref ref-type="bibr" rid="ref12 ref7">(e.g., Hartigan and Wong, 1979; Elkan, 2003)</xref>
        or
sequential pattern-mining algorithms like Apriori-based
algorithms
        <xref ref-type="bibr" rid="ref18 ref20 ref30">(e.g., Slimani and Lazzez, 2013)</xref>
        . Moreover, to
support the visualisation and analysis of reviews and their
components, domain-specific modelling approaches
        <xref ref-type="bibr" rid="ref11 ref14">(e.g.,
Guizzardi et al., 2002; Kishore and Sharman, 2004)</xref>
        can be
valuable further research directions.
      </p>
      <p>As a result, this study provides a double contribution to the
field of Digital Humanities: First, the category system and
the first sample annotations constitute a starting point for a
classification of textual components of reviews, and for its
subsequent automation by means of machine learning
methods. Second, this study and the ongoing research
project which it is a part of go beyond the methodological
questions and address—by examining digital practices of
cultural participation through reviews—the understanding
of digital culture and society on a more fundamental level
which is, eventually, a central question of Digital
Humanities.</p>
      <p>7.</p>
    </sec>
    <sec id="sec-8">
      <title>Conclusion</title>
      <p>
        In order to identify components that are contained in
reviews of cultural artefacts, we used the coding paradigm
in the sense of Grounded Theory
        <xref ref-type="bibr" rid="ref10 ref32 ref33">(e.g., Glaser, 1978;
Strauss and Corbin, 1990, 1998)</xref>
        . We thus empirically
derived components by analysing and annotating selected
reviews. These components then have been structured,
resulting in a multi-layered category system. To evaluate
the system, we applied the categories, annotating several
reviews and we modified the system up to a stable version.
As a result, the system contains Layer 1—Content, Layer
2—General Criticism, Layer 3—Style and Layer 4—
Further Information. Each layer consists of several
categories that are organized in tree-like hierarchies. To
further evaluate the category system, students applied the
resulting system, annotating about 430 Amazon book
reviews. The measurement of the absolute agreement of
each category provides first insights into the
comprehensibility of the categories. Thus, it supports
revising the category system.
      </p>
      <p>Overall, our findings contribute to the ongoing research on
reviews in the digital world and to the analysis and
characterisation of reviews of cultural artefacts. Based on
the category system and on sample annotations, researchers
are further able to identify the review components
automatically with methods of machine learning and to
discover patterns of review components.</p>
      <p>8.</p>
    </sec>
    <sec id="sec-9">
      <title>Acknowledgements</title>
      <p>This research was conducted in the scope of the research
project “Rez@Kultur” (01JKD1703), which is funded by
the German Federal Ministry of Education and Research
(BMBF). We would like to thank them for their support.</p>
    </sec>
  </body>
  <back>
    <ref-list>
      <ref id="ref1">
        <mixed-citation>
          <string-name>
            <surname>Boser</surname>
            ,
            <given-names>B. E.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Guyon</surname>
            ,
            <given-names>I. M.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Vapnik</surname>
            ,
            <given-names>V. N.</given-names>
          </string-name>
          (
          <year>1992</year>
          ).
          <article-title>A training algorithm for optimal margin classifiers</article-title>
          .
          <source>In Proceedings of the fifth annual workshop on Computational learning theory. ACM</source>
          , pages
          <fpage>144</fpage>
          -
          <lpage>152</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref2">
        <mixed-citation>
          <string-name>
            <surname>Charmaz</surname>
            ,
            <given-names>K.</given-names>
          </string-name>
          (
          <year>2006</year>
          ).
          <article-title>Constructing Grounded Theory. A Practical Guide Through Qualitative Analysis</article-title>
          .
          <source>SAGE.</source>
        </mixed-citation>
      </ref>
      <ref id="ref3">
        <mixed-citation>
          <string-name>
            <surname>Cho</surname>
            ,
            <given-names>Y. H.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Jae</surname>
            ,
            <given-names>K. K.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Soung</surname>
            ,
            <given-names>H. K.</given-names>
          </string-name>
          (
          <year>2002</year>
          ).
          <article-title>A personalized recommender system based on web usage mining and decision tree induction</article-title>
          .
          <source>Expert systems with Applications</source>
          , (
          <volume>23</volume>
          :3):
          <fpage>329</fpage>
          -
          <lpage>342</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref4">
        <mixed-citation>
          <string-name>
            <surname>Cortes</surname>
            ,
            <given-names>C.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Vapnik</surname>
            ,
            <given-names>V.</given-names>
          </string-name>
          (
          <year>1995</year>
          ).
          <article-title>Support-vector networks</article-title>
          .
          <source>Machine learning</source>
          , (
          <volume>20</volume>
          :3):
          <fpage>273</fpage>
          -
          <lpage>297</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref5">
        <mixed-citation>
          <string-name>
            <surname>Deloitte</surname>
          </string-name>
          (
          <year>2007</year>
          ).
          <article-title>New Deloitte Study Shows Inflection Point for Consumer Products Industry; Companies Must Learn to Compete in a More Transparent Age</article-title>
          . Press Release, Deloitte
          <string-name>
            <surname>Services</surname>
            <given-names>LP</given-names>
          </string-name>
          , New York, October 1.
        </mixed-citation>
      </ref>
      <ref id="ref6">
        <mixed-citation>
          <string-name>
            <surname>Duan</surname>
            ,
            <given-names>W.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Gu</surname>
            ,
            <given-names>B.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Whinston</surname>
            ,
            <given-names>A. B.</given-names>
          </string-name>
          (
          <year>2008</year>
          ).
          <article-title>Do online reviews matter? An empirical investigation of panel data</article-title>
          .
          <source>In Decision Support Systems</source>
          .
          <volume>45</volume>
          ., pages
          <fpage>1007</fpage>
          -
          <lpage>1016</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref7">
        <mixed-citation>
          <string-name>
            <surname>Elkan</surname>
            ,
            <given-names>C.</given-names>
          </string-name>
          (
          <year>2003</year>
          ).
          <article-title>Using the Triangle Inequality to Accelerate k-Means</article-title>
          .
          <source>In Proceedings of the International Conference on Machine Learning</source>
          , Washington DC, USA.
        </mixed-citation>
      </ref>
      <ref id="ref8">
        <mixed-citation>
          <string-name>
            <surname>Fleiss</surname>
            ,
            <given-names>J. L.</given-names>
          </string-name>
          (
          <year>1971</year>
          ).
          <article-title>Measuring Nominal Scale Agreement among many Raters</article-title>
          .
          <source>Psychological Bulletin</source>
          ,
          <volume>76</volume>
          (
          <issue>5</issue>
          ):
          <fpage>378</fpage>
          -
          <lpage>382</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref9">
        <mixed-citation>
          <string-name>
            <surname>Fleiss</surname>
            ,
            <given-names>J. L.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Cohen</surname>
            ,
            <given-names>J.</given-names>
          </string-name>
          (
          <year>1973</year>
          ).
          <article-title>The Equivalence of weighted Kappa and the Intraclass Correlation Coefficient as Measures of Reliability</article-title>
          .
          <source>Educational and Psychological Measurement</source>
          ,
          <volume>33</volume>
          :
          <fpage>613</fpage>
          -
          <lpage>619</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref10">
        <mixed-citation>
          <string-name>
            <surname>Glaser</surname>
            ,
            <given-names>B. G.</given-names>
          </string-name>
          (
          <year>1978</year>
          ).
          <article-title>Theoretical sensitivity</article-title>
          . Mill Valley, CA: The Sociology Press.
        </mixed-citation>
      </ref>
      <ref id="ref11">
        <mixed-citation>
          <string-name>
            <surname>Guizzardi</surname>
            ,
            <given-names>G.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Ferreira</surname>
            <given-names>Pires</given-names>
          </string-name>
          , L. and
          <string-name>
            <surname>Van Sinderen</surname>
            ,
            <given-names>M. J.</given-names>
          </string-name>
          (
          <year>2002</year>
          ).
          <article-title>On the role of domain ontologies in the design of domain-specific visual modeling languages</article-title>
          .
          <source>In Proceedings of the ACM OOPSLA.</source>
        </mixed-citation>
      </ref>
      <ref id="ref12">
        <mixed-citation>
          <string-name>
            <surname>Hartigan</surname>
            ,
            <given-names>J. A.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Wong</surname>
            ,
            <given-names>M. A.</given-names>
          </string-name>
          (
          <year>1979</year>
          ).
          <article-title>Algorithm AS 136: A K-Means Clustering Algorithm</article-title>
          .
          <source>Journal of the Royal Statistical Society</source>
          , Series C (Applied Statistics)
          <volume>28</volume>
          (
          <issue>1</issue>
          ):
          <fpage>100</fpage>
          -
          <lpage>108</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref13">
        <mixed-citation>
          <string-name>
            <surname>He</surname>
            ,
            <given-names>R.</given-names>
          </string-name>
          and
          <string-name>
            <surname>McAuley</surname>
            ,
            <given-names>J.</given-names>
          </string-name>
          (
          <year>2016</year>
          ).
          <article-title>Ups and downs: Modeling the visual evolution of fashion trends with one-class collaborative filtering</article-title>
          .
          <source>In Proceedings of the 25th international conference on world wide web</source>
          , pages
          <fpage>507</fpage>
          -
          <lpage>517</lpage>
          , InternationalWorldWideWeb Conferences Steering Committee.
        </mixed-citation>
      </ref>
      <ref id="ref14">
        <mixed-citation>
          <string-name>
            <surname>Kishore</surname>
            ,
            <given-names>R.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Scharman</surname>
            ,
            <given-names>R.</given-names>
          </string-name>
          (
          <year>2004</year>
          ).
          <source>Computational Ontologies and Information Systems. Foundations. Communications of the Association for Information Systems</source>
          ,
          <volume>14</volume>
          (
          <issue>8</issue>
          ):
          <fpage>158</fpage>
          -
          <lpage>183</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref15">
        <mixed-citation>
          <string-name>
            <surname>Klinger</surname>
            ,
            <given-names>R.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Suliya</surname>
            ,
            <given-names>S. S.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Reiter</surname>
            ,
            <given-names>N.</given-names>
          </string-name>
          (
          <year>2016</year>
          ).
          <article-title>Automatic Emotion Detection for Quantitative Literary Studies -- A case study based on Franz Kafka's „Das Schloss“ und „Amerika“</article-title>
          . In Digital Humanities, Kraków, Poland.
        </mixed-citation>
      </ref>
      <ref id="ref16">
        <mixed-citation>
          <string-name>
            <surname>Krippendorff</surname>
            ,
            <given-names>K.</given-names>
          </string-name>
          (
          <year>2011</year>
          ).
          <article-title>Agreement and Information in the Reliability of Coding</article-title>
          .
          <source>Communication Methods and Measures</source>
          ,
          <volume>5</volume>
          (
          <issue>2</issue>
          ):
          <fpage>1</fpage>
          -
          <lpage>20</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref17">
        <mixed-citation>
          <string-name>
            <surname>Kutzner</surname>
            ,
            <given-names>K.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Schoormann</surname>
            ,
            <given-names>T.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Knackstedt</surname>
            ,
            <given-names>R.</given-names>
          </string-name>
          (
          <year>2018</year>
          ).
          <article-title>Digital Transformation in Information Systems Research: A Taxonomy-based Approach to Structure the Field</article-title>
          .
          <source>In European Conference on Information Systems</source>
          , Portsmouth, UK.
        </mixed-citation>
      </ref>
      <ref id="ref18">
        <mixed-citation>
          <string-name>
            <given-names>La</given-names>
            <surname>Roche</surname>
          </string-name>
          ,
          <string-name>
            <given-names>W.</given-names>
            ,
            <surname>Hooffacker</surname>
          </string-name>
          ,
          <string-name>
            <given-names>G.</given-names>
            and
            <surname>Meier</surname>
          </string-name>
          ,
          <string-name>
            <surname>K.</surname>
          </string-name>
          (
          <year>2013</year>
          ).
          <article-title>Einführung in den praktischen Journalismus: Mit genauer Beschreibung aller Ausbildungswege Deutschland Österreich Schweiz</article-title>
          . Springer-Verlag.
        </mixed-citation>
      </ref>
      <ref id="ref19">
        <mixed-citation>
          <string-name>
            <surname>March</surname>
            ,
            <given-names>S. T.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Smith</surname>
            ,
            <given-names>G.</given-names>
          </string-name>
          (
          <year>1995</year>
          ).
          <source>Design and Natural Science Research on Information Technology. Decision Support Systems</source>
          ,
          <volume>15</volume>
          (
          <issue>4</issue>
          ):
          <fpage>251</fpage>
          -
          <lpage>266</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref20">
        <mixed-citation>
          <string-name>
            <surname>McAuley</surname>
            ,
            <given-names>J.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Leskovec</surname>
            ,
            <given-names>J.</given-names>
          </string-name>
          (
          <year>2013</year>
          ).
          <article-title>Hidden Factors and Hidden Topics: Understanding Rating Dimensions with Review Text</article-title>
          .
          <source>In Proceedings of the 7th ACM Conference on Recommender Systems</source>
          , pages
          <fpage>165</fpage>
          -
          <lpage>172</lpage>
          , New York NY, USA, ACM.
        </mixed-citation>
      </ref>
      <ref id="ref21">
        <mixed-citation>
          <string-name>
            <surname>McAuley</surname>
            ,
            <given-names>J.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Targett</surname>
            ,
            <given-names>C.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Shi</surname>
            ,
            <given-names>Q.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Van Den Hengel</surname>
            ,
            <given-names>A.</given-names>
          </string-name>
          (
          <year>2015</year>
          ).
          <article-title>Image-based recommendations on styles and substitutes</article-title>
          .
          <source>In Proceedings of the 38th International ACM SIGIR Conference on Research and Development in Information Retrieval</source>
          , pages
          <fpage>43</fpage>
          -
          <lpage>52</lpage>
          , ACM.
        </mixed-citation>
      </ref>
      <ref id="ref22">
        <mixed-citation>
          <string-name>
            <surname>Mehling</surname>
            ,
            <given-names>G.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Kellermann</surname>
            ,
            <given-names>A.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Kellermann</surname>
            ,
            <given-names>H.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Rehfeldt</surname>
            ,
            <given-names>M.</given-names>
          </string-name>
          (
          <year>2018</year>
          ).
          <article-title>Leserrezensionen auf amazon</article-title>
          .de : Eine teilautomatisierte inhaltsanalytische Studie. Bamberg, Bamberg University Press.
        </mixed-citation>
      </ref>
      <ref id="ref23">
        <mixed-citation>
          <string-name>
            <surname>Nielsen</surname>
          </string-name>
          (
          <year>2012</year>
          ).
          <article-title>Nielsen's latest Global Trust in Advertising report</article-title>
          . https://retelur.files.wordpress.com/
          <year>2007</year>
          /10/global-trustin-advertising-
          <year>2012</year>
          .pdf (downloaded
          <year>2018</year>
          -
          <volume>04</volume>
          -30).
        </mixed-citation>
      </ref>
      <ref id="ref24">
        <mixed-citation>
          <string-name>
            <surname>O'Reilly</surname>
            ,
            <given-names>T.</given-names>
          </string-name>
          (
          <year>2005</year>
          ).
          <article-title>What is the Web 2</article-title>
          .0?, URL: http://www.oreilly.com/pub/a//web2/archive/whatisweb-20.html (downloaded
          <year>2018</year>
          -
          <volume>06</volume>
          -15).
        </mixed-citation>
      </ref>
      <ref id="ref25">
        <mixed-citation>
          <string-name>
            <surname>Pfohlmann</surname>
            ,
            <given-names>O.</given-names>
          </string-name>
          (
          <year>2005</year>
          ).
          <article-title>Kleines Lexikon der Literaturkritik</article-title>
          . Verlag LiteraturWissenschaft.de.
        </mixed-citation>
      </ref>
      <ref id="ref26">
        <mixed-citation>
          <string-name>
            <surname>Pang</surname>
            ,
            <given-names>B.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Lee</surname>
            ,
            <given-names>L.</given-names>
          </string-name>
          (
          <year>2008</year>
          ).
          <article-title>Opinion Mining and Sentiment Analysis</article-title>
          .
          <source>Foundations and Trends in Information Retrieval</source>
          ,
          <volume>2</volume>
          (
          <issue>1</issue>
          -2):
          <fpage>1</fpage>
          -
          <lpage>135</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref27">
        <mixed-citation>
          <string-name>
            <surname>Peffers</surname>
            ,
            <given-names>K.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Tuunanen</surname>
            ,
            <given-names>T.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Rothenberger</surname>
            ,
            <given-names>M.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Chatterjee</surname>
            ,
            <given-names>S.</given-names>
          </string-name>
          (
          <year>2007</year>
          /
          <year>2008</year>
          ).
          <source>A Design Science Research Methodology for Information Systems Research. Journal of Management Information Systems</source>
          ,
          <volume>24</volume>
          (
          <issue>3</issue>
          ):
          <fpage>45</fpage>
          -
          <lpage>77</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref28">
        <mixed-citation>
          <string-name>
            <surname>Rasoul</surname>
            ,
            <given-names>S. S.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Landgrebe. D.</surname>
          </string-name>
          (
          <year>1991</year>
          ).
          <article-title>A survey of decision tree classifier methodology</article-title>
          .
          <source>In IEEE transactions on systems, man, and cybernetics</source>
          , (
          <volume>21</volume>
          :3):
          <fpage>660</fpage>
          -
          <lpage>674</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref29">
        <mixed-citation>
          <string-name>
            <surname>Rauterberg</surname>
            ,
            <given-names>H.</given-names>
          </string-name>
          (
          <year>2007</year>
          ).
          <article-title>Und das ist Kunst?!: eine Qualitätsprüfung</article-title>
          .
          <source>Frankfurt am Main, S. Fischer Verlag.</source>
        </mixed-citation>
      </ref>
      <ref id="ref30">
        <mixed-citation>
          <string-name>
            <surname>Slimani</surname>
            ,
            <given-names>T.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Lazzez</surname>
            <given-names>A.</given-names>
          </string-name>
          (
          <year>2013</year>
          ).
          <article-title>Sequential Mining: Patterns and Algorithms Analysis</article-title>
          .
          <source>International Journal of Computer and Electronics Research</source>
          ,
          <volume>2</volume>
          (
          <issue>5</issue>
          ):
          <fpage>639</fpage>
          -
          <lpage>647</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref31">
        <mixed-citation>
          <string-name>
            <surname>Stegert</surname>
            ,
            <given-names>G.</given-names>
          </string-name>
          (
          <year>1997</year>
          ).
          <article-title>Die Rezension: Zur Beschreibung einer komplexen Textsorte</article-title>
          .
          <source>Beiträge zur Fremdsprachenvermittlung</source>
          ,
          <volume>31</volume>
          :
          <fpage>89</fpage>
          -
          <lpage>110</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref32">
        <mixed-citation>
          <string-name>
            <surname>Strauss</surname>
            ,
            <given-names>A.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Corbin</surname>
            ,
            <given-names>J.</given-names>
          </string-name>
          (
          <year>1990</year>
          ).
          <article-title>Basics of qualitative research: Grounded theory procedures and techniques</article-title>
          . Newbury Park, CA,
          <year>Sage</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref33">
        <mixed-citation>
          <string-name>
            <surname>Strauss</surname>
            ,
            <given-names>A.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Corbin</surname>
            ,
            <given-names>J.</given-names>
          </string-name>
          (
          <year>1998</year>
          ).
          <article-title>Basics of qualitative research: Grounded theory procedures and techniques</article-title>
          . Thousand Oaks, CA,
          <year>Sage</year>
          ,
          <volume>2nd</volume>
          <fpage>edition</fpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref34">
        <mixed-citation>
          <string-name>
            <surname>Toffler</surname>
            ,
            <given-names>A.</given-names>
          </string-name>
          (
          <year>1980</year>
          ).
          <article-title>The Third Wave: The Revolution That Will Change Our Lives</article-title>
          . London/New York, Collins.
        </mixed-citation>
      </ref>
      <ref id="ref35">
        <mixed-citation>
          <string-name>
            <surname>Wiegand</surname>
            ,
            <given-names>M.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Ruppenhofer</surname>
            ,
            <given-names>J.</given-names>
          </string-name>
          (
          <year>2015</year>
          ).
          <article-title>Opinion Holder and Target Extraction based on the Induction of Verbal Categories</article-title>
          .
          <source>In Proceedings of the 19th Conference on Computational Language Learning</source>
          , pages
          <fpage>215</fpage>
          -
          <lpage>225</lpage>
          , Beijing, China, Association for Computational Linguistics.
        </mixed-citation>
      </ref>
    </ref-list>
  </back>
</article>