<!DOCTYPE article PUBLIC "-//NLM//DTD JATS (Z39.96) Journal Archiving and Interchange DTD v1.0 20120330//EN" "JATS-archivearticle1.dtd">
<article xmlns:xlink="http://www.w3.org/1999/xlink">
  <front>
    <journal-meta>
      <journal-title-group>
        <journal-title>and Chih-Jen Lin.
2008. LIBLINEAR: A Library for Large Linear Classification. Journal of Machine
Learning Research 9 (2008)</journal-title>
      </journal-title-group>
    </journal-meta>
    <article-meta>
      <title-group>
        <article-title>Summarizing Game Reviews: First Contact</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Aris Kosmopoulos</string-name>
          <email>akosmo@scify.org</email>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>George Giannakopoulos</string-name>
          <email>ggianna@iit.demokritos.gr</email>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Antonios Liapis</string-name>
          <email>antonios.liapis@um.edu.mt</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Nikiforos Pittaras</string-name>
          <email>npittaras@di.uoa.gr</email>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Institute of Digital Games, University of Malta</institution>
          ,
          <addr-line>Msida</addr-line>
          ,
          <country country="MT">Malta</country>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>NCSR Demokritos and Kapodistrian University of Athens</institution>
          ,
          <addr-line>Athens</addr-line>
          ,
          <country country="GR">Greece</country>
        </aff>
        <aff id="aff2">
          <label>2</label>
          <institution>SciFY PNPC and NCSR Demokritos</institution>
          ,
          <addr-line>Athens</addr-line>
          ,
          <country country="GR">Greece</country>
        </aff>
      </contrib-group>
      <pub-date>
        <year>2019</year>
      </pub-date>
      <volume>1</volume>
      <fpage>143</fpage>
      <lpage>161</lpage>
      <abstract>
        <p>In recent years the number of players that are willing to submit a video game review has increased drastically. This is due to a combination of factors such as the raw increase of video gamers and the wide use of gaming platforms that facilitate the review submission process. The vast data produced by reviewers make extracting actionable knowledge dificult, both for companies and other players, especially if the extraction is to be completed in a timely and eficient manner. In this paper we experiment with a game review summarization pipeline that aims to automatically produce review summaries through aspect identification and sentiment analysis. We build upon early experiments on the feasibility of evaluation for the task, designing and performing the first evaluation of its kind. Thus, we apply variants of a main analysis pipeline on an appropriate dataset, studying the results to better understand possible future directions. To this end, we propose and implement an evaluation procedure regarding the produced summaries, creating a benchmark setting for future works on game review summarization.</p>
      </abstract>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>CCS CONCEPTS</title>
      <p>• Applied computing → Computer games; • Computing
methodologies → Information extraction.
summarization, natural language processing, sentiment analysis,
game reviews, Steam.</p>
    </sec>
    <sec id="sec-2">
      <title>INTRODUCTION</title>
      <p>
        The ever-expanding popularity of digital games is evidenced by the
large profit margins of the commercial game industry sector [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ],
the vast and diverse swathes of the population that play games [17],
and the appeal of games and gamification beyond the purposes
of entertainment [13]. A large factor for the market penetration
of digital games are distribution platforms such as Steam and the
Google Play Store. Not only do these distribution platforms allow
interested players to purchase and download new games, they also
cultivate a player community with players returning to rate and
comment on their favorite game or even contribute user-created
content, strategies, cheats, etc. This community-driven content
often informs other users’ purchases (e.g. via an aggregated review
score) but is also carefully monitored by developers and publishers
in order to gauge opinions on specific aspects of the game which
can be patched or improved in updates to the game or in sequels. For
both players and developers, being able to succinctly monitor other
players’ views is highly beneficial. The website www.metacritic.com
aggregates reviews by players and professional critics, returning
a percentage score for the game and highlighting diverse reviews
along the spectrum of positive versus negative. The Steam platform
also aggregates its users’ reviews into diferent categories (‘Mixed’,
‘Overwhelmingly Positive’, ‘Mostly Negative’ etc.) which is another
criterion for sorting and (likely) promoting games. The simple
aggregation of reviews into a general score is important, but it
obfuscates the nuances of the diferent reviewers’ grievances and
is of limited use to designers who wish to improve their game.
This paper explores techniques for text summarization in order
to provide a multi-dimensional and holistic summary of Steam
reviews for a particular game.
      </p>
      <p>We explore the topic of summarization for game reviews
using a large dataset of Steam reviews from 12 selected games. The
goal of the summarization pipeline is to extract users’ views on
diferent facets of games such as graphics, audio, and gameplay
[28], leveraging textual sentiment analysis to identify and
positive and negative review snippets, creating a composite summary
of indicative comments on a specific game facet. Unlike the
numerical aggregation of Metacritic or Steam, this approach extracts
individual sentences (and criticisms) contained within a usually
dense review and attempts to classify those in terms of positive
or negative automatically (rather than based on the user’s binary
recommendation). The presentation of the game’s summary, which
is split based on diferent aspects typically criticized in games, can
be valuable for both players and designers. For players, the
statistics derived from this process (e.g. ratio of positive versus negative
comments in one aspect) can act as an expanded game scoring
system not unlike professional game reviews which gave a score to
graphics, audio etc. For designers, the indicative comments split per
sentiment and aspect allows for a quick monitoring of players’
current favorite features. Moreover, the flexible way in which aspects
are defined allows designers to explicitly redefine the keywords
they are interested in, personalizing the summary to their design
priorities.</p>
      <p>
        There has been very limited attention to game review
summarization, besides student projects [
        <xref ref-type="bibr" rid="ref32">55</xref>
        ]. Inspired by the only work
that performs aspect-based game review summarization [
        <xref ref-type="bibr" rid="ref27">50</xref>
        ], this
paper evaluates the outcomes of a straightforward summarization
pipeline in a small-scale user survey. Using the twelve most
reviewed games in a 2017 dataset of Steam reviews, the resulting
summaries are evaluated by a small set of experts. The paper
studies pipeline variants to better sketch what is important in game
review summarization. Based on the outcomes of the diferent
summarization processes, and a small-scale study where the diferent
outcomes were compared, a number of potential improvements
were identified. The paper also highlights the many directions
which game review summarization research can follow so that it
can serve designers and players through diferent pipeline
implementations, alternative visualizations, bottom-up aspect discovery,
or text processing driven by domain knowledge.
      </p>
      <p>The paper is structured as follows. We start with a review of
related works in Section 2. We then describe the proposed
summarization pipeline and variants in Section 3. We describe the dataset
in Section 4 and present two diferent user studies in Sections 5 and
6. We then discuss the results in Section 7 and conclude the paper
in Section 8.
2</p>
    </sec>
    <sec id="sec-3">
      <title>RELATED WORK</title>
      <p>
        User reviews are a rich source of information, although the
extraction and analysis of this information can be challenging not only
due to the textual nature of the medium but also because users tend
to have a mixed opinion about various features [31]. Approaches
such as sentiment analysis as well as summarization have been
applied to various datasets, such as product reviews [24, 31], movie
reviews [
        <xref ref-type="bibr" rid="ref30 ref31">53, 54</xref>
        ], or hotel reviews [25]. Section 2.1 surveys relevant
approaches for the diferent phases of a summarization pipeline,
while Section 2.2 discusses the nuances of the Steam platform and
early work in game review summarization. For interested readers,
[25] provides a more thorough overview on review summarization
according to the type of corpora used as input.
2.1
      </p>
    </sec>
    <sec id="sec-4">
      <title>Summarization Pipeline</title>
      <p>
        Summarization can be extractive when relevant portions (usually
sentences) of the input are copied and combined, or abstractive
when new text is generated to rephrase and summarize the input
[18]. The summarization pipeline requires a number of steps before
the raw textual input can produce a summary; algorithms and
approaches for each step are discussed below.
2.1.1 Pre-processing and parsing. A fundamental step towards
summarization (and natural language processing more broadly) is the
pre-processing and extraction of features from the dataset. In the
analysis below, the term documents is used to describe any type of
text, e.g. a sentence, a paragraph, or an academic paper. One
popular if naive approach for pre-processing data is the bag-of-words
which collects all words in the document, disregarding their order
and grammar. This method counts the number of instances of the
same word, and the frequency of occurrence of each word is used
as a feature to measure similarity between documents. Since many
words (such as articles or pronouns) are far more frequent in all
documents, terms are weighted based on their frequency via tf.idf
[
        <xref ref-type="bibr" rid="ref18">41</xref>
        ] where the term frequency (  ) is multiplied by the inverse
document frequence (  ). Unlike the bag-of-words approach, the
word order is considered in many other approaches as it can capture
a word’s importance. For instance, the first and last sentences in a
larger document tend to be more important [33]. Other approaches
tag words on their part-of-speech (POS) [
        <xref ref-type="bibr" rid="ref14">37</xref>
        ], e.g. nouns (NN), verbs
(VB), or adverbs (RB). This is useful for pre-processing, e.g. selecting
only sentences with a noun and adjective as a corpus for review
summarization [25]. Another use of POS tags is to select N-grams
(i.e. a sequence of words) with specific parts of speech, such as a
comparative adverb followed by an adjective [
        <xref ref-type="bibr" rid="ref24">47</xref>
        ].
2.1.2 Topic Modeling. Identifying the topic of a document,
sentence, or review is often necessary for clustering opinions on the
topic together. When the topics of interest are known in advance,
experts usually provide the keywords used to filter the relevant
documents. For instance, TweetElect used an initial set of 38 keywords
related to the 2016 US elections (including candidates’ names) for
streaming relevant tweets [
        <xref ref-type="bibr" rid="ref11">11</xref>
        ]. However, a boolean check whether
a keyword is specifically mentioned is rarely suficient due to the
nuances of language; query expansion is applied to create a larger set
of terms related to each original keyword [29]. Supervised learning
is often applied for topic modelling, showing positive and negative
examples of relevant documents to a classifier [ 29]. When topics are
unknown and must be discovered from the data, a simple approach
is to identify the most frequent terms and cluster emergent terms
based on co-occurrence [16]. Probabilistic topic models such as
Latent Dirichlet Allocation (LDA) [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ] can more eficiently discover
topics without domain knowledge, following a bag-of-words
approach which disregards word or document order. LDA randomly
chooses a set of topics and decomposes the probability
distribution matrix of words in a document into two matrices consisting
of the distribution of topics in a document and the distribution of
words in a topic. Due to the vast number of possible topic structures,
sampling-based algorithms are used to find the sample topics which
best approximate the posterior distribution [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ]. LDA has often been
applied to find topics within reviews, primarily in order to identify
review’s sentiments towards these topics, e.g. in [26].
2.1.3 Sentiment Analysis. The sentiment behind utterances is
important for summarization, especially when the corpus is reviews
of any kind. Turney [
        <xref ref-type="bibr" rid="ref24">47</xref>
        ] highlighted that reviews may recommend
or not a certain product, movie, or travel destination; a summary
therefore should account for both positive and negative reviews.
Turney’s study was the first to perform sentiment analysis on
textbased reviews based on responses of the AltaVista internet search
query on how near the phrases were to the word ‘excellent’ (for
recommended) and the word ‘poor’ (for not recommended).
Manually created lexica for words that express sentiment have been
used in conjunction with fuzzy logic, vector distance, etc. to
classify positive and negative [
        <xref ref-type="bibr" rid="ref22">12, 45</xref>
        ]. In the same context, there has
been extensive work on extracting opinion words which express
subjective opinions within sentences [
        <xref ref-type="bibr" rid="ref26">49</xref>
        ]. It has been found that
subjective sentences are statistically correlated with the presence
of adjectives [
        <xref ref-type="bibr" rid="ref26">49</xref>
        ], and much research in product review
summarization uses adjectives to determine sentiment polarity. For instance,
Hu et al. [24] used a frequency-based algorithm to find relevant
domain features, and then extracted nearby adjectives to such
domain features. Using a labeled set of adjectives and expanding the
initial set via WordNet, Hu et al. classified the extracted adjectives’
polarity and assigned that positive or negative sentiment to the
nearby domain feature. The SentiWordNet database is constructed
based on the same principles of the domain-specific adjective
classification of [ 24], using a manually annotated set of seed words and
using WordNet term relationships to expand the training set, which
is then used as the ground truth for machine learning classifiers [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ].
SentiWordNet, and similar general-purpose models for sentiment
prediction [
        <xref ref-type="bibr" rid="ref23">46</xref>
        ], have been used for polarity detection in reviews,
e.g. in [
        <xref ref-type="bibr" rid="ref17">23, 40</xref>
        ].
2.2
      </p>
    </sec>
    <sec id="sec-5">
      <title>Steam Review Summarization</title>
      <p>Since its 2003 release, the Steam platform has become the largest
digital distribution platform for PC gaming [15], hosting over 34,000
games and tens of millions of active users daily. This paper
focuses on user-created reviews on Steam, although other initiatives
such as the Steam workshop allow users to upload their mods or
strategies and comment on others’ content. User reviews can be
submitted only by people that have purchased the game from Steam,
although they are visible to all. As noted above, Steam aggregates
user reviews into a category and provides a number of companion
statistics, including a timeline of reviewer’s scores. Reviews
themselves consist of a single binary recommendation (Recommended
versus Not Recommended) and a text explaining the user’s opinion.
Other users can review the quality of the review itself by tagging it
helpful, not helpful, funny, or breaking the Rules of Conduct. By
default, Steam shows the most helpful reviews submitted within
the last 30 days, although users can also choose to sort reviews by
other criteria.</p>
      <p>
        As noted in the introduction, there is no systematic academic
research in Steam review summarization. To the best of our
knowledge, the only academic publication that tackles the problem of
aspect-based summarization on such data is by Yauris and
Khodra [
        <xref ref-type="bibr" rid="ref27">50</xref>
        ]. In their approach, only relevant portions of sentences
were extracted via conditions applied on text tagged via Parts of
Speech; these portions were usually small, e.g. the phrase could be
“amount of content” [
        <xref ref-type="bibr" rid="ref27">50</xref>
        ]. Similar to our approach, a pre-specified
set of keywords are used for aspect categorization. The aspects
and keywords are similar but not identical to our approach (e.g.
the aspects in [
        <xref ref-type="bibr" rid="ref27">50</xref>
        ] are gameplay, story, graphic, music, community,
and general/others), while choosing the aspect described in the
phrase was based on the cosine similarity from each word of the
phrase to the aspect’s keywords. The output summary consists
of many aspects (most of which are outside the pre-specified
keywords) and a single adjective for each, unlike our current work
which extracts complete sentences with diferent polarities. The
summarization pipeline was tested on a single game (Skyrim),
exploring diferent sentiment extraction approaches using precision
and recall as performance metrics. While our current work does not
explore as many parameters for sentiment analysis, it is the first
instance where game review summaries are evaluated by humans
in a small-scale but thorough user study.
3
      </p>
    </sec>
    <sec id="sec-6">
      <title>SUMMARIZATION PIPELINES</title>
      <p>Preprocessing which aims to prepare the input reviews for
further analysis. This may imply cleaning, chunking text
in snippets or sentences, Part-of-Speech tagging, and other
similar tasks.</p>
      <p>Aspect Identification which identifies interesting aspects (or
topics) in the reviews. These topics may be expressed as a
set of words, e.g. "visual, aesthetic, scenery" or "soundscape,
audio experience, "sound efects".</p>
      <p>Aspect Labeling which assigns clear, descriptive labels to the
discovered aspects. E.g. "graphics", "audio".</p>
      <p>Sentiment Analysis which gathers information related to the
sentiment expressed within the reviews. This information
may later be used to update the final summary appropriately.
For example, one may need only positive views in the
summary, or—most probably—a sampling of all the views, be
they positive or negative.</p>
      <p>Summary Creation which implies the process which, given
all the information gathered in previous steps, forms and
renders the final summary for the user.</p>
      <p>Given the above pipeline, we implemented three diferent
variants. The first two are based on keyword detection and Clustering
(CL). The first variant does not do Sentiment Analysis, while the
second one uses the full pipeline. The last one is another full pipe
method based on Deep Learning (DL) that focuses on improving on
Aspect Labeling and Summary Creation steps.
3.1</p>
    </sec>
    <sec id="sec-7">
      <title>CL pipeline</title>
      <p>
        During the preprocessing step, each review is split into sentences,
each sentence is cleaned in order to create the basic elements on
which the final summaries will be based. The cleaning process
included of some character replacements so that each sentence
could be presentable (e.x. starting with a capital letter and ending
with a period) even if it originated from a larger sentence that was
split during sentence splitting. Moreover, preprocessing prepared
the lemmatized versions of the sentences which are used for aspect
detection. In these lemmatized sentences, general stop words are
removed. For all preprocessing steps, we used the default functions
(and stop word lists) of the nltk Python library [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ].
      </p>
      <p>The aspect detection process is split into two parts: aspect
identification and aspect labeling. Aspect identification splits sentences
into sets that focus on a specific aspect while aspect labeling
identifies this aspect in order to present it to the final review summary.</p>
      <p>Our approach uses a predefined set of aspects, presented in
Table 1. We selected these six aspects since they are well-established
facets of games [28] and are popular dimensions within professional
reviews.</p>
      <p>
        A simple approach for aspect labeling is to use a dictionary of
keywords per aspect as the ones presented in Table 1. In order to
be able to include sentences even when they do not include the
exact keywords, a k-means clustering is applied to all sentences to
ifnd clusters with similar text. Terms are weighted based on their
frequency via   .  , which has been used extensively for sentence
similarity in bag-of-words approaches (see Section 2.1). The result
is  clusters of sentences with similar words to each other; in all
our experiments we set  = 20 based on prior evidence [
        <xref ref-type="bibr" rid="ref12">35</xref>
        ]. Once
sentences are all assigned a cluster based on the distance to the
center, all sentences in all clusters are processed in the following
fashion:
Community
      </p>
      <p>Graphics</p>
      <p>Community</p>
      <p>Graphics</p>
      <sec id="sec-7-1">
        <title>1 Review</title>
      </sec>
      <sec id="sec-7-2">
        <title>Preprocessing</title>
      </sec>
      <sec id="sec-7-3">
        <title>2 Aspect</title>
      </sec>
      <sec id="sec-7-4">
        <title>Iden fica on</title>
        <p>Gameplay</p>
      </sec>
      <sec id="sec-7-5">
        <title>3 Aspect</title>
      </sec>
      <sec id="sec-7-6">
        <title>Labeling</title>
        <p>Gameplay</p>
      </sec>
      <sec id="sec-7-7">
        <title>4 Sen ment</title>
      </sec>
      <sec id="sec-7-8">
        <title>Analysis</title>
      </sec>
      <sec id="sec-7-9">
        <title>5 Summary</title>
      </sec>
      <sec id="sec-7-10">
        <title>Crea on</title>
        <p>(1) If the sentence contains the exact keywords of only one
aspect, the sentence is assigned to that aspect and is flagged
as a candidate that can be used by the summary of that
aspect.
(2) If keywords from multiple aspects are found in the sentence,
the sentence is flagged as an unsuitable candidate for any
summary and removed.
(3) If no aspect keywords are found in the sentence, the most
common aspect within the sentences of the same cluster will
be used to label this sentence and flag it as a candidate. For
instance, if a sentence does not contain any keyword, but
sentences in its cluster predominantly belong to the aspect
Gameplay via case (1), then the sentence is also assigned to
the same aspect and flagged as a candidate.</p>
        <p>Using the sentences from cases (1) and (3), a set of candidate
sentences is created per aspect. Using these sets, the first
variation of our pipeline could now produce a summary. This variation,
named Clustering Aspect Detection summary (CL AsDe), chooses
 sentences at random from each aspect’s set. A sample CL AsDe
summary can be found in Table 2 for Tom Clancy’s The Division.</p>
        <p>
          The next step of the process is Sentiment Analysis, which is used
by the next summarization variant (CL Full). Using the diferent sets
of candidate sentences per aspect, the sentiment polarity (positive or
negative) of each sentence is calculated by averaging the sentiment
score of each word it contains. As above, sentiment analysis of each
word is done via the default functions of the nltk Python library [
          <xref ref-type="bibr" rid="ref5">5</xref>
          ].
The library calculates probabilities for each polarity class (positive,
neutral, negative). We took into account sentences which were
assigned a class with a probability of at least 0.5. In order to select
a number of sentences per category, a -means clustering approach
(using   .  ) is applied within the set of sentences with the same
polarity. In the CL Full implementation of this paper, only two
sentences per polarity are selected ( = 2) as the ones closest to
each cluster’s centroid. If there exist suficient positive and negative
sentences, then this approach returns 6 sentences as bullet points.
Note that if fewer than two sentences are above the threshold for
positive (or below the threshold, for negative) then fewer sentences
may be included in the summary. An example summary from CL
Full variant can be found in Table 2 for Tom Clancy’s The Division.
3.2
        </p>
      </sec>
    </sec>
    <sec id="sec-8">
      <title>DL pipeline</title>
      <p>After experimenting with the first two variant pipelines and taking
into account the feedback of the first user study (see Section 5), we
decided to focus on improving the following:
• Keyword detection and clustering based Aspect Labeling
must be improved to avoid sentences such as "If those things
all sound good to you you will like the game." to be labeled
as audio sentences.
• The final summary should somehow provide information
regarding the whole sentiment of the given aspect and not
just by the selected sentences.
• The final summary should use a better sentence extraction
approach in order to deal with redundancy.</p>
      <p>Taking all the above into account, the DL pipeline makes changes
to the Aspect Detection and Summary Creation steps of the CL
pipeline described in Section 3.1.</p>
      <p>
        For Aspect Detection, we used the BERT model [14] to generate
embeddings for game reviews. BERT is a deep neural language
model that uses a bidirectional, multilayer transformer architecture,
exploiting cross and self-attention to capture word
interdependencies efectively [
        <xref ref-type="bibr" rid="ref25 ref3">3, 48</xref>
        ]. The approach relies on multi-head attention
modules for sequence encoding modelling, with word order
information being retained with additive positional encoding vectors.
BERT is trained in an unsupervised setting on large quantities of
English text, using masked language modelling and next sentence
prediction objectives. These tasks require the prediction of hidden
sequence tokens and the generation of an entire sequence, given an
input sequence (e.g. for tasks such as question-answering and text
entailment, etc.). This pretraining scheme and architecture have
been shown to perform exceptionally well for a variety of natural
language understanding tasks.
      </p>
      <p>To obtain the representation for a game review, we feed the text
to the model using a sequence length of 16 tokens. We use the
 model variant, that produces 768-dimensional sequence
embeddings, learned during training for classification purposes.
The implementation and pretrained model utilized are provided by
the transformers software package from huggingface1. Using the
produced embeddings as features we trained a binary Ridge Logistic
Regression classifier [ 19] (one vs all) for each aspect. We also trained
a seventh classifier to detect sentences unfit for any aspect. For each
candidate sentence a confidence score was calculated by each aspect
classifier. Only sentences with a high prediction confidence in the
given aspect and a low confidence on each other classifier were
selected as summary candidates for the next steps of the pipeline.</p>
      <p>During the Summary Creation we applied the following
strategy to the 100 most probable candidate sentences of each aspect.
First, the NewSum Toolkit [20] was used to select the sentences
that provide the most representative information. NewSum uses
language-agnostic methods based on n-gram graphs, that not only
extract the most representative sentences, but also deal with
redundancy. In the end we had 20 candidate sentences per Aspect. The
ifnal summary was composed by 6 sentences using the following
strategy:
• Select the most positive sentence (Sentiment Analysis).
• Select the most negative sentence (Sentiment Analysis).
• Select the first 3 sentences provided by NewSum Tookit
(excluding the previously selected sentences).
• Create an artificial sentence using the polarities provided by
Sentiment Analysis of all the aspect sentences. The polarity
of each sentence was mapped as 1, 0 or -1 (positive, neutral,
negative) using thresholds. Given an Aspect and the mean
Polarity score ¯  , the possible produced sentences reflect
opinions that fall in the following categories:
1https://huggingface.co/
- In a few words the game is single dimensional this might sound vague but it
becomes apparent that there is not much depth as you play once you’re a couple
hours in.
- Clothes sound "right" when you move in them.
- They sound good and looked good with ability to mod for better stats or even
rerolling stats.
- They have improved the pve portion of the game and crazy as it sounds the pvp
too.
- No music and something feels so strangely abandnded about it.
- Like how if there’s a blizzard your cap and shoulder will be covered in snow and
that npc voices will echo when they are standing in hallways with hollow walls.
- Very good voice acting.
- Great abilities pretty good sounds; indoor echos reverb of objects etc.
- If those things all sound good to you you will like the game.
- Superb voice acting and ambient city sounds are also a good plus for this game.
- It sounds hyperbolic but I’m being dead serious.
- Sounds terrible right
- Most opinions are positive regarding audio.
- The voice acting in the game is in the higher tiers as is most ubisoft games.
- There are not a lot of diferent voices and some of the voice acting for them is
bad.
- Ubisoft - bugs - the textures are so fucked up that nobody can play this game
anymore.
- And it clearly shows I want to play it and that I try to.</p>
      <p>-I’m gonna be honest the cinematics are pretty great.</p>
      <p>Table 2: Summaries generated by diferent pipelines, for
aspect Audio of Tom Clancy’s The Division. From top to
bottom: CL AsDe (only aspect detection), CL Full (aspect
detection with sentiment analysis) and DL Full (Deep learning
combined with a sophisticated summarizer).</p>
      <p>- Mixed: ¯  ≈ 0, high standard deviation.
- Mostly neutral: ¯  ≈ 0, low standard deviation.
- Mostly positive: ¯  &gt; 0 above a threshold.</p>
      <p>- Mostly negative: ¯  &lt; 0 below a threshold.</p>
      <p>The final summary is composed by randomly shufling these 6
sentences. An example summary from DL Full variant can be found
in Table 2 for Tom Clancy’s The Division.</p>
    </sec>
    <sec id="sec-9">
      <title>4 DATASET</title>
      <p>
        As a first demonstration of the summarization pipeline, we follow
[
        <xref ref-type="bibr" rid="ref12">35</xref>
        ] and select the most helpful reviews on Steam, splitting them per
game. This paper parses the Steam review dataset gathered by Zuo
[
        <xref ref-type="bibr" rid="ref32">55</xref>
        ], which consists of over 7 million reviews obtained via Steam’s
API. Each review text comes with a plethora of features concerning
both the game being reviewed and the reviewer, although only a
subset of features is used for this experiment. Since Steam users
can vote a review as helpful, unhelpful, or spam, we only consider
‘valid’ reviews those with 10 or more user votes as ‘helpful’. With
this criterion (minimum of at least 1000 of ‘helpful’ reviews), we
select twelve games with the most valid reviews (see Table 3). The
games selected have a desirable diversity both in terms of genres
(shooting, survival, adventure, open-world, multi-player,
singleplayer, etc.) and in terms of general audience reception (shown
by the Metacritic score which aggregates professional and users’
reviews).
      </p>
      <p>For each of the selected games we selected to keep the 10
thousand most up-voted reviews. As already discussed in Section 3 each
of these reviews was split into sentences to create a sentence pool
per game. On average, the sentence pool consisted of around 50
thousand sentences per game. The smallest pool of sentences was
for PAYDAY 2 (37K), while the largest one was for Elite Dangerous
(70K). The average length of the sentences was 85.7 in characters
and 16.4 in words. In terms of both characters and words, the longest
sentences were those of Darkest Dungeon (average of 91.8
characters and 17.3 words) and the shortest ones were those of Just
Survive (average of 79.9 characters and 15.6 words).</p>
      <p>In terms of aspects, the most common one was Gameplay on
average. Performance was the next most popular aspect and in certain
games such as ARK: Survival Evolved it was the most popular one.
The least popular aspect was Audio with a ratio of 1 to 5 compared
to the Gameplay aspect.</p>
      <p>In terms of sentiment, the majority of sentences were more
neutral than positive or negative. Between positive and negative
sentiment, no general safe conclusions can be drawn since the
results varied given diferent combinations of aspects and games.
In general, we can say that the aspect Performance was
characterized as negative more frequently. The opposite was true for the
aspect Graphics. On the other hand the sentiment ratio (positive vs
negative) towards the aspect Community varied between diferent
games.
5</p>
    </sec>
    <sec id="sec-10">
      <title>FIRST USER STUDY</title>
      <p>As a first experiment, we evaluated the two variations of the CL
pipeline (CL AsDe and CL Full) in a small-scale user-study with
summaries of aspects of the 12 games of Table 3.
5.1</p>
    </sec>
    <sec id="sec-11">
      <title>Annotation Protocol</title>
      <p>
        A pairwise comparison process was followed, rather than a
scalebased rating approach, due to (a) evidence that comparison-based
evaluation can be less demanding cognitively [
        <xref ref-type="bibr" rid="ref9">9</xref>
        ] and (b) a rich body
of literature that has applied pairwise evaluation for summarization
tasks [34] (e.g. the single document summarization task in [21]).
      </p>
      <p>To this end, we created an online evaluation user interface (UI)
(see Figure 2) which supported comparative pairwise evaluation
of summaries. We initialized the system by providing two sets
of summaries A, B, one from system  and one from system .
Each summary in A corresponded to a summary in B, as they both
summarize the same set of reviews and the same aspect (e.g. the
aspect Graphics of DayZ). During the experiment, each system’s
summary was randomly placed first or second to minimize any bias
related ordering efect.</p>
      <p>The UI also informed the user of the title of the game being
summarized, plus the aspect (e.g. Graphics). The user was then
called to select their preferred summary (A or B) and explain the
reasons for this preference. For the latter annotation, the user could
select one or more tickboxes among the following options:
• It repeats less the same information (Less Redundant)
• It seems to be more coherent and/or complete
• For other (or even unclear) reasons</p>
      <p>
        The first two options aim to assess whether redundancy is a
concern and, similarly, whether coherence and completeness are useful
in the task. Redundancy has been traditionally a summarization
evaluation indicator [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ], especially in multi-document
summarization. The completeness and coherence aspect is essentially a (more
nuanced) version of overall responsiveness, as this has been used
in DUC/TAC summarization tracks and related work [
        <xref ref-type="bibr" rid="ref10">10</xref>
        ].
5.2
      </p>
    </sec>
    <sec id="sec-12">
      <title>Participants</title>
      <p>The evaluation was carried out by eight adult evaluators (3 female),
lfuent in English, with gaming experience. The evaluators were
selected explicitly among the authors’ network of contacts and
invited directly by the authors. Participants were asked to connect to
the online system and evaluate all 72 pairs of summaries (produced
by CL AsDe and CL Full), which covered all predefined aspects (see
Table 1) of the ten games in Table 3. There was no time limit for
completing the evaluation, but there was a requirement that all
pairs were evaluated in a single session.
5.3</p>
    </sec>
    <sec id="sec-13">
      <title>Results</title>
      <p>The data collected from the experiment was a total of 576
observations, including the preference of each evaluator for each pair
of summaries and the reasons for this choice. The primary goals
of the user study are to assess (a) whether the annotators prefer
one of the two summarization approaches, (b) which criteria they
explicitly (via the three tickboxes) or implicitly (based on properties
of the summary) consider when selecting their preference. Towards
this end, the data is processed based on the 8 users’ annotations
on 72 game/aspect pairs (for a total of 576 data points), and all
statistical tests are performed at a 5% significance threshold. Our
assumption is that the complete CL pipeline which includes both
aspect detection and sentiment analysis will ofer a richer and more
diverse summary than AsDe alone.</p>
      <p>Regarding users’ preference of one summarization technique,
results were mixed: overall, annotators had no clear preference with
CL AsDe being marginally more often selected (53%). Table 4 shows
the distribution of selection of CL Full split per aspect. The Table
shows that the main factor for the skew of the overall preference
towards CL AsDe was the graphics summaries, as the other aspects
are fairly evenly preferred between the two approaches.</p>
      <p>To further assess which factors led to the annotators’ preference
of one summary over the other, we conducted an analysis of
variance test (ANOVA) between the preferred approach (represented
as a binary choice) and other features such as the aspect. Table 5
shows the results in terms of significant diferences, and verifies
that there is a systematic influence between the aspect and
preference. On the other hand, the game does not seem to afect users’
preference of one summary or the other; this is a promising finding
as the methods are supposed to be applicable to any game. There
is also a clear evidence that preference was highly varying from
annotator to annotator, and annotators rarely agreed with each
other even in this simple pair-wise preference task.</p>
      <p>To get a better understanding of the reasons annotators gave
regarding their preference, we looked further into the statistics
of the winning observations of CL AsDe vs. CL Full. When AsDe
was preferred, annotators explained their preference mainly due to
better coherence (63%), lower redundancy (28%), but also ‘other
reasons’ (26%). When CL Full was preferred, annotators chose ‘other
reasons’ (50%), and less often coherence (41%) or low redundancy
(17%). This finding shows that summaries by AsDe were more
coherent but annotators still preferred summaries by CL Full often
for other reasons. This points to a limitation of the experimental
protocol, as the interface did not provide annotators with enough
options to allow them to explain their reasons for their summary
preference. This was addressed in the second user study (see
Section 6) with an extra option on the UI. It should be noted that better
coherence was selected far more often overall (53% of instances)
than lower redundancy (23%), while ‘other reasons’ were also
chosen often (37%). Redundancy and coherence were chosen together
in only 5% of instances, and thus it is evident that these two axes of
evaluation are fairly independent. These findings, coupled with the
statistically significant influence (via ANOVA) between preference
of summarization approach and tagged coherence and redundancy,
support our conclusion that both coherence and redundancy were
important factors for annotators’ preference.
6</p>
    </sec>
    <sec id="sec-14">
      <title>SECOND USER STUDY</title>
      <p>Based on the findings and limitations identified in the first user
study, conducted a second study with more participants but fewer
games, testing the best CL approaches with the novel DL Full
pipeline. Due to participants’ concerns on the long duration of
the 72-item survey in the first experiment, we opted to use only
two games to lower the time required from annotators; it is
expected that fatigue would likely introduce noise to the participants’
responses. Details on how the games and annotation options were
chosen are detailed in Section 6.1.
6.1</p>
    </sec>
    <sec id="sec-15">
      <title>Annotation Protocol</title>
      <p>The user interface for the second user study was largely the same as
in the first (see Section 5.1). Based on the first study’s finding that
‘other reasons’ for an annotator’s preference were often chosen, a
fourth option was added to the UI as a tickbox stating “The summary
was more focused and contained less irrelevant information.” We
refer to this additional option as Focus in the analysis that follows.</p>
      <p>As noted above, to reduce the time required for the study only
two games were chosen to be annotated. We chose among the
games from the first user study, taking the game where CL Full had
the highest preference (Tom Clancy’s The Division, where CL Full
was chosen 60% of the time) and the game where CL AsDe had the
highest preference (Elite Dangerous, where CL AsDe was chosen
60% of the time). For each of the two games, the preferred method
was chosen to present to the user, juxtaposed with the summary
for the same game and aspect produced by DL Full. Therefore, the
participant had to annotate 12 items, 6 aspects for Tom Clancy’s the
Division comparing the CL Full summary with the DL Full summary
and 6 aspects for Elite Dangerous comparing the CL AsDe summary
with the DL Full summary. The rationale was to select the most
successful game summaries (for both CL variants) and compare
them with the novel DL pipeline. We refer to CL and DL summaries
in this paper, referring to the best CL summary (CL Full or CL AsDe)
as shown to the user.</p>
      <p>As with the first user study, the order of the two options was
randomized (i.e. sometimes CL summaries were shown first,
sometimes second). Unlike the previous experiment, however, the order
of the sentences within the same summary was also randomized;
the rationale was to avoid ordering efects when the participant
starts by reading an incoherent sentence first.
6.2</p>
    </sec>
    <sec id="sec-16">
      <title>Participants</title>
      <p>Fourteen participants completed this annotation task. Unlike the
previous study, a snowball method for soliciting participants was
followed, soliciting feedback from a broader group. Thus, this study
lacks data on the demographics and gaming experience of
participants, although participants were all adults and had experience in
data analysis and artificial intelligence.
6.3</p>
    </sec>
    <sec id="sec-17">
      <title>Results</title>
      <p>The data collected from the experiment was a total of 168
observations. Overall CL summaries were slightly more preferred by
participants (55%), although the diference is not statistically
significant (Paired t-test, p-value 0.22). Interestingly, for Elite Dangerous
(which was summarized by CL AsDe) the diference was more
pronounced (CL AsDe preferred 60% of the time over DL Full); for Tom
Clancy’s The Division the two methods (CL Full and DL Full) were
chosen evenly. Since only one game was tested per CL variant, it
is dificult to assess whether the preference was due to the game
itself or the sentiment-based selection component. Moreover, while
DL Full includes sentiment-based selection, this part accounts for 2
of the 6 sentences and thus it is even more dificult to estimate the
reasons for the users’ preference. This ambiguity points to further
refinements needed for the annotation protocol which is discussed
in Section 7.</p>
      <p>In terms of the reasons ofered by participants for their choice,
coherence was still most commonly chosen (62% of responses),
followed closely by focus (56%). Low redundancy was chosen less
often (23%), while ‘other reasons’ are chosen only in 14% of
responses). The addition of the focus option seems to have mitigated
the prevalence of ‘other reasons’ in the first study. Unlike the first
study, however, low redundancy was often chosen in conjunction
with one other reason (56% of the time) or two other reasons (36%
of the time). Combined with its low overall prevalence, it is possible
that low redundancy may now longer be necessary as a separate
reason in the UI, although a broader user study with more games
is needed to validate this hypothesis.</p>
      <p>Pearson’s Chi-squared tests were also used in order to test whether
any of the above reasons is correlated to the preferred summary.
Only redundancy was found to be correlated with the type of
summary (p-value 0.001). This clearly indicates the importance of
handling redundancy satisfyingly in any future approach.
7</p>
    </sec>
    <sec id="sec-18">
      <title>DISCUSSION</title>
      <p>This paper introduced a number of possible pipelines for
identifying, grouping, and extracting the opinions of users in terms
of pre-specified game facets. two small-scale user surveys
examined the preference of users in the presence of diferent pipeline
implementations. Results indicate that (a) aspect extraction is
important for summarization, although deep-learning does not
necessarily improve the aspect extraction process compared to a simpler
clustering-based method; (b) between the clustering-based pipeline
variants (CL AsDe, CL Full), there was no clear winner with respect
to the summary outputs; (c) evaluators had strong and individual
opinions on which variant was better; (d) sentiment-based
criteria and/or confidence-based criteria for selecting sentences do not
seem to perform better than the random selection performed by CL
AsDe.</p>
      <p>
        While the aspects chosen for this experiment were intuitive,
based on typical facets of games that players and professional
critics focus on, some of the resulting aspect-based summaries were
less coherent than others. The choice to assign a sentence to an
aspect even if its cluster only had a slim majority in keyword
frequency likely introduced inconsistency. For CL aspect detection,
the most significant factor for the lack of coherence was the choice
of keywords. Specifically, the keyword “sound” was often found in
sentences unrelated to game audio, used as a verb: e.g. “On paper
this game sounds great”. To a degree, such artefacts were removed in
the DL aspect detection pipeline via (a) the latent sentence
representation and (b) fine-tuning the model based on manual annotations
on this specific corpus. However, a more sophisticated method for
aspect detection seems necessary. For instance, an adaptive query
expansion as followed by [29] could create a much larger set of
keywords automatically, although it may overlook the nuances of game
terminology. On the other hand, a Word2Vec model [30] trained
on the entire corpus of steam reviews (or even larger game-related
corpora such as game FAQs and fansites) could be used to derive
a similarity score with specific aspects. Building a game ontology
for this task or using an existing one [
        <xref ref-type="bibr" rid="ref13 ref16">36, 39</xref>
        ] could further assist
in discovering more keywords or in calculating an ontology-based
semantic similarity measure [
        <xref ref-type="bibr" rid="ref19">42</xref>
        ]. Finally, a completely diferent
direction could see the discovery of topics specific to each game
rather than focusing on the same pre-specified topics every time.
This would be valuable as diferent genres have a diferent focus
(e.g. multiplayer games focus on balance or lag, while horror games
focus on the emotional response), but could make it dificult to
maintain the same presentation format across games and thus confuse
end-users.
      </p>
      <p>
        Sentiment analysis was also often problematic, primarily due to
the informal and idiosyncratic language that games reviews were
often in. Reviews are often rife with sarcasm and negation, e.g. “Have
fun spending huge amounts of hours for very little progress.”.
Moreover, many reviews’ sentences have poor syntax and are very short
or very long (e.g. “Good: + great aesthetic.”). Sentiment analysis
treated the sentence as a bag-of-words, exacerbating the problem. In
general, sentiment analysis can not capture negation or sarcasm and
handles incomplete sentences poorly. Performance would likely be
improved with a more appropriate pre-trained lexicon for informal
utterances on the Social Web, such as SentiStrength [
        <xref ref-type="bibr" rid="ref23">46</xref>
        ] or other
sentiment- and negation-aware approaches [22]. Alternatively, a
custom classifier for sentiment analysis could be trained using text
from a Steam review as input and the user’s recommendation as
polarity. Complementing the training set with experts’ annotations
could refine such a model, especially when dealing with sarcasm.
Another promising alternative to SentiWordNet for sentiment
analysis would be the use of an authored dictionary of opinion words
[24] or game-specific adjectives annotated in terms of polarity [
        <xref ref-type="bibr" rid="ref28">51</xref>
        ].
      </p>
      <p>Our findings also showed no clear winner between the two CL
variants or between CL and DL summaries. These ambiguity of the
ifndings could well be by-products of the experimental protocol
followed. Findings from the first user study pointed to a missing
reason for players to report, and the second study included a “focus”
reason which improved the quality of the data collected but raised
questions about the importance of the “low redundancy” reason.
The users’ reported fatigue in the first experiment led to fewer
items in the second study to alleviate the burden from annotators.
However, this increased the locality of the findings in the second
study as it was unclear whether preferences were due to the game or
the algorithm. In future studies, summaries for more games should
be annotated by more participants, showing only two games to each
user but randomizing which games are shown when the user starts
the study. More importantly, the current experimental protocol
forces participants to select one review as preferred and provide
at least one reason. The forced choice between two summaries
does not allow the user to provide more nuanced feedback. A
fouralternative forced-choice (4-AFC) with options “A”, “B”, “both A and
B”, “neither A nor B” would allow the user to point out cases where
both summaries are equally good or equally bad. The fairly even
split between the two alternatives in both user studies could be due
to fact that users consider some summaries shown equally bad and
select randomly. On the other hand, a 4-AFC questionnaire would
likely need many more participants since much of the data will
be removed when no ranking is given. The need for more games,
more annotation choices, and perhaps more algorithm variants (DL
AsDe, for instance) point to the need for a large-scale user survey
among the general gaming community, which will be performed in
future work in this vein.</p>
      <p>As discussed in Section 1 and explored on a high-level during
the user study, game review summarization can be valuable both
to consumers (players) and producers (game developers). However,
each stakeholder has diferent priorities and will likely respond
diferently to diferent summary formats. The extractive
summarization process was visualized as ‘pure text’ bullet points, which was
not as engaging to either type of audience. It would be important
to explore alternative visualizations for players and developers. For
players, the summary could provide more structure (based on
prespecified game facets), focus more on the weights and scoring of
each aspect (including visualizations such as pie-charts), show only
a few polar opposites in terms of review sentences, and perhaps
cross-reference these findings with other games’ review summaries.
For developers, on the other hand, a bottom-up topic discovery
would likely be beneficial in order to identify unexpected points of
contention among users. Moreover, presenting the context of the
reviewers’ chosen sentences would also be valuable for designers,
e.g. how many reviewers agree with or echo this comment, when
this comment was made and whether general sentiment has shifted
since then. Such context can be important regarding the urgency
of addressing certain concerns or to gauge whether patches and
updates have improved reviewers’ perception, not unlike Steam’s
use of most recent reviews.</p>
      <p>
        There are many directions for future research depending on the
purpose of the game review summarization. As a tool for game
evaluation, primarily targeted towards players or producers, the game’s
context is important in order to choose which reviews or topics to
highlight. Additional research in this vein would need to find topics
or patterns in similar games (e.g. of the same genre, publisher, or
publication date) and then to compare the current game’s reviews
in terms of those topics or compared to other games’ reviews. User
experience research would also be important to find how best to
present such results, as interactive summaries where the user can
zoom in and out into diferent games and/or diferent topics within
games would make the summaries more intuitive and manageable.
As a tool for game analysis, bottom-up probabilistic topic modelling
[
        <xref ref-type="bibr" rid="ref7">7</xref>
        ] in games of the same genre could help identify design patterns
[
        <xref ref-type="bibr" rid="ref6">6</xref>
        ] and players’ expectations based on their repertoire [27]. As a
tool for knowledge discovery, game reviews can serve as raw text
or multi-modal corpora from which structured data can be
automatically extracted as entities and relations [
        <xref ref-type="bibr" rid="ref21">44</xref>
        ], concept hierarchies
[
        <xref ref-type="bibr" rid="ref20 ref29">43, 52</xref>
        ], or even a complete game ontology [
        <xref ref-type="bibr" rid="ref15">32, 38</xref>
        ].
      </p>
    </sec>
    <sec id="sec-19">
      <title>8 CONCLUSION</title>
      <p>This paper highlighted the challenges and opportunities of game
review summarization via natural language processing. The paper
introduced a pipeline for grouping Steam users’ comments into
pre-specified aspects such as visuals or performance, and studied
diferent renderings of the final summary, exploiting positive and
negative sentences based on sentiment analysis. The small-scale
user survey revealed diferences in how diferent annotators assess
the reviews, highlighted possible foci of research for better game
review summarization systems, and suggested a number of
refinements to the process are suggested in this promising subfield of
game artificial intelligence.</p>
    </sec>
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