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Service-Oriented Architecture (SOA) is a set of practices for architectural design of software that exploits services as loosely coupled components orchestrated to deliver various functionalities. The SOA paradigm is not well established in the Serious Games (SG) domain, but it is expected to provide benefits, particularly in reducing the conceptual and technological complexity of the development. In this paper, we propose and study the application of a SOA approach to SG development. We have used the SOA approach to develop an adaptive serious game for teaching basic elements of probability to high school and entry-level university students, called The Journey. Details of the architecture implementation are offered, as well as the results of an evaluation of the system using the Architecture Tradeoff Analysis Method (ATAM). Based on our experience, we argue that the SOA approach can make SG development shorter, more flexible and more focused.
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A case study on Service-Oriented Architecture for
Serious Games
Maira B. Carvalhoa,b,
, Francesco Bellottia, Riccardo Bertaa, Alessandro De
Gloriaa, Giorgia Gazzarataa, Jun Hub, Michael Kickmeier-Rustc
aDITEN, University of Genoa, Via Opera Pia 11A, 16145, Genoa, Italy
bIndustrial Design, Eindhoven University of Technology, P.O. Box 513, 5600 MB
Eindhoven, The Netherlands
cKnowledge Technologies Institute, Graz University of Technology, Inffeldgasse 13/5th floor
8010, Graz, Austria
Abstract
Service-Oriented Architecture (SOA) is a set of practices for architectural
design of software that exploits services as loosely coupled components orches-
trated to deliver various functionalities. The SOA paradigm is not well estab-
lished in the Serious Games (SG) domain, but it is expected to provide benefits,
particularly in reducing the conceptual and technological complexity of the de-
velopment. In this paper, we propose and study the application of a SOA
approach to SG development. We have used the SOA approach to develop an
adaptive serious game for teaching basic elements of probability to high school
and entry-level university students, called The Journey. Details of the archi-
tecture implementation are offered, as well as the results of an evaluation of
the system using the Architecture Tradeoff Analysis Method (ATAM). Based
on our experience, we argue that the SOA approach can make SG development
shorter, more flexible and more focused.
Keywords: adaptive serious games, games for learning, serious games, serious
games development, service oriented architecture, architecture tradeoff
analysis method
NOTICE: this is the author’s version of a work that was accepted for publication in Enter-
tainment Computing. Changes resulting from the publishing process, such as peer review,
editing, corrections, structural formatting, and other quality control mechanisms may not be
reflected in this document. Changes may have been made to this work since it was submit-
ted for publication. A definitive version has been published in Entertainment Computing 6
(2015) 1–10, DOI:10.1016/j.entcom.2014.11.001.
Corresponding author
Email address: m.brandao.carvalho@tue.nl (Maira B. Carvalho)
Preprint submitted to Entertainment Computing January 17, 2015
1. Introduction
Games are gaining increasing importance as educational and training tools.
Serious Games (SGs) as games used for purposes other than to simply entertain
are often called [1] have been shown to have a lot of potential in education [2, 3,
4], offering the possibilities of making learning more engaging and satisfying [5].
Among the benefits are their role in engaging and motivating learners [2] and
their ability to expose learners to experiences that would be impossible, unsafe
or at least impractical to reproduce in the real world [1, 6, 7]
However, there is still a long way to make SGs widely deployed, especially be-
cause of the high development costs. In this paper, we propose the application
of a Service Oriented Architecture (SOA) approach to serious game develop-
ment as a desirable and beneficial solution for the field, resulting in efficient
development and high quality products. In SOA, software is built as a set of
independent, loosely coupled components that provide self-contained function-
alities (services) to other components and applications. By employing the core
principles of SOA, such as modularization and compositionality, we expect to
achieve flexibility in the development of serious games and to enable the reuse
of software parts. The SOA principles are already widely and successfully em-
ployed in several areas of software engineering, but the examples in the SG
domain are limited.
To illustrate the benefits of the SOA approach in SG development, we re-
port a case study on the use of a web service based on the Competence-based
Knowledge Space Theory (CbKST) [8] to develop an adaptive serious game for
teaching basic elements of probability to high school and entry-level univer-
sity students, called The Journey. The paper also presents the results of an
evaluation of the system employing the Architecture Tradeoff Analysis Method
(ATAM), using the conclusions of the evaluation to give an account of the con-
straints, benefits and changes in the programming paradigm that are relevant
to SG development.
In short, the novelty presented here consists of a demonstration of how the
SOA approach can improve the process of SG development through component
reuse, and how it can enhance product quality by enabling the implementation
of features that are still rare in SGs, such as adaptation techniques, learning
analytics, social media integration, etc.
This paper is organized as follows. In the next section, we define Service
Oriented Architectures and list its possible benefits and drawbacks in SG de-
velopment. Section 3 presents a compilation of projects using SOA or simi-
lar approaches. In Section 4, we discuss the concept of adaptivity in learn-
ing environments and present the Competence-based Knowledge Space Theory
(CbKST), explaining how it can be used in adaptive SGs. Subsequently, we
describe the game The Journey, offering details of its architecture and imple-
mentation. Section 6 presents an ATAM evaluation of the system architecture
and discusses the benefits and drawbacks of applying SOA in SG development.
Finally, we present the discussion and conclusion of our work and pointers for
future research.
2
2. Service Oriented Architectures
A Service-Oriented Architecture (SOA) is “a software architecture that im-
plements business processes or services by using a set of loosely coupled, black-
box components orchestrated to deliver a well-defined level of service” [9]. It is
a set of ideas, recommendations, policies and practices for architectural design.
One of its goals is to employ modularization and compositionality to achieve
flexibility and to enable the reuse of software parts, in an attempt to manage
the complexity of large systems [10, 11].
The benefits of using a SOA approach are many. Unlike the case of tradi-
tional library reuse, which requires replication of code, SOA supports reuse of
the services themselves, which provides a significant benefit in terms of hav-
ing up-to-date components without concerns about maintenance of the code.
In addition, it supports such a level of abstraction that multiple services can
offer the same functionalities, potentially giving the developer a wider choice
of providers from which to obtain the service needed. Furthermore, SOA es-
tablishes standardized contracts between endpoints, placing formal obligations
between consumer and provider and largely increasing reusability and interop-
erability. An implementation that complies to known web service standards
(e.g. REST or SOAP) has additional benefits, such as standardization, technol-
ogy/platform neutrality and automatic discovery and use [10]. The automatic
binding of services removes compile-time dependencies; the interface definition
happens in runtime, removing the need to alter the code every time when there
is a change in the service provider. This provides flexibility in the development
and improves maintainability [12, 13].
In the specific case of game development, a SOA approach can bring the
potential benefit of decreased interdependencies and usage dependent payment
models [14]. Furthermore, it facilitates dealing with scalability issues, which
is particularly relevant to online games in which several thousands of players
interact in a common platform, as the increased load in the servers may bring
performance concerns [14]. SOA also makes it possible to access games from
simple devices, eliminating the dependency on the quality of gaming hardware.
In addition, providing pervasive gaming experiences becomes easier, as support
for different platforms is highly simplified if the core of the gaming experience
is provided via a service in a centralized server [15].
Educational applications in general not only SGs can also benefit from
the application of SOA [16, 17]. In addition to the points listed above, the
most relevant advantage is the possibility to reuse educational components and
domain-independent features (e.g. shared user profiles, knowledge databases
on learning topics, natural language processing dialog services), which could
potentially be deployed as web services that could be composed and invoked by
a learning application or game when needed.
There are, nevertheless, challenges in adopting a service-oriented architec-
ture. Quality assurance and testing module integration tend to be more difficult
when developing SOA applications [9]. In addition, a service can be practically
unusable if its interfaces lack clarity or are badly documented. Finally, extra
attention has to be given to service descriptions, as they are the way to ad-
vertise the capabilities, interfaces, behavior and quality of a service, providing
the required information for discovery, selection, binding and composition with
other components [18].
3
3. Related work
Service-based architectures are already widely and successfully employed
in several areas of software engineering, including game development. There
is an increasing availability of service-based tools for game development, such
as cloud-based infrastructure for building, deployment and distribution [19],
platforms providing social connectivity to games [20] and services that provide
generic gaming features such as achievements, leaderboards and cloud saving
[21, 22].
Although there are clear benefits in employing service-based architectures to
SG development, the examples of deployments of SOA-based SGs are limited.
This is true even if there are several gaming-related services already available
and a large number of (non-educational) digital games already utilizing those
services.
While not necessarily SOA-based, decoupling the content of the SG from the
underlying gaming software is a way of facilitating the extensibility of SGs and
to support domain experts in the creation of content, which can then happen
independently of the development of the game itself [23]. The project Travel in
Europe (TiE), for example, proposes an architecture style that supports both
code reuse and consistent interaction modalities across games [24, 25, 26]. The
MetaVals Serious Game, a game for practicing basic finance concepts, consists of
a modular database and an independent graphic interface, with a management
interface that facilitates configuring the game to different contexts [27].
Authoring platforms also aim to reduce the complexity of game develop-
ment. The eAdventure game platform serves as an authoring platform for edu-
cational point-and-click adventure games, executing games defined in a special-
ized markup language [28, 29]. The authoring tool Puzzle-it divides the process
of developing games into content authoring and core engine development, mak-
ing it possible for instructors to create content for the games via the authoring
tool without needing to be concerned about engine behind the games [30].
When it comes to the actual usage of SOA in SGs, examples available are
very few.
While the game itself has not been developed, a Service-Oriented Architec-
ture was the approach of choice for an envisioned gaming platform based on mo-
bile augmented reality, called MARL. In this system, on-demand location-based
instruction would be delivered through a head-mount display by a virtual in-
structor. The complete MARL game service would be composed of subsystems
that would provide visual, human computer interface, and training services,
allowing for the lower level objects to be encapsulated by the higher level inter-
faces, making it easier for improvements in the algorithms to be incorporated
into the service [31].
The Rashi Intelligent Tutoring System teaches human anatomy through a
problem-based environment. Rashi is built as a web service architecture that
supports on-demand requests for small chunks of specific knowledge, instead of
requests for an entire case specification at once, giving developers flexibility to
develop lightweight inquiry tutors that run efficiently over the web [32]. On
top of the same existing service structure for the original (2D) inquiry system,
the researchers built a 3D game in which the student is a doctor who must
diagnose a patient in a virtual hospital. Despite being limited to a specific type
of learning (i.e. problem-based inquiry), Rashi constitutes one of the very few
4
examples of service-based architecture for game-based education, demonstrating
well the benefits of the SOA approach for SG development.
The Serious Games Society has developed the Serious Games Web Services
Catalog [33], a repository of web services with the associated documentation and
example applications. The catalog does not host any of the services, but rather
acts as a showcase for services available from the providers, serving as a central
hub for publishing and discovery of the currently available technologies. The
effort aims to facilitate the communication between Serious Game developers
among themselves and with educators, encouraging the application of the SOA
approach to SG development.
4. Implementing competence-based adaptation in Serious Games
In order to investigate the development of SOA-based SGs, we have focused
on competence-based adaptation in the learning environment, which is a highly
relevant pedagogic feature [5, 34], not yet widely employed in the SGs domain.
Implementing adaptation in SGs, especially in low to medium scale projects,
is costly, both in terms of conceptual and technological complexity as well as
in design and implementation efforts. Therefore, efforts should be made to
make it easier and cheaper equipping SGs with features to enable intelligent
adaptation techniques for learning. Thus, applying a SOA approach is expected
to be beneficial, as it would allow using a single user profiling module supporting
adaptivity for different SGs.
4.1. Adaptive Serious Games
Adaptivity in the context of learning and education refers to the adjustment
of the instruction according to the learner’s responses and performance, in an
attempt to achieve superior performance of tailored tutoring when compared to
regular teaching [35]. In game-based learning, equipping SGs with adaptation
capabilities aims to create more effective games by providing an adequate level
of challenge to the player, neither too hard, causing frustration, nor too easy,
causing boredom [5].
Experimental findings have shown that equipping SGs with adaptive features
results in superior educational gains and gaming experience [36]. The same
results have been observed by a meta-review of more than 300 scientific articles
on the educational efficacy of computer games: the vast majority (90%) of
the games that reported non-trivial educational results displayed some form of
educational adaptation or personalization [5].
In-game adaptation for learning can be different than the style of adapta-
tion implemented in traditional virtual learning environments. Some authors
propose the implementation of a subtle style of in-game adaptation, based on
assessing the continuous interaction of the learner with the game, using ob-
servable evidences (i.e. the process of play itself) to infer knowledge, skills or
other attributes. The objective is to not disrupt the game flow with tests or
interventions that are not smoothly embedded in the game [37, 38].
4.2. Competence-based Knowledge Space Theory (CbKST)
The Competence-based Knowledge Space Theory (CbKST) is an approach to
formative, competence-centered assessment that comes from the non-numerical
5
and non-linear approach of the Knowledge Space Theory (KST) [8]. The idea
of CbKST is to assume a finite set of roughly atomic competences that is, well-
defined, small scale descriptions of aptitude, ability, knowledge, or skill and a
prerequisite relation between those competences, which defines the competence
model of the domain.
Due to the prerequisite relations, not all subsets of competences are possible
competence states. This structure is an advantage from the computational
point of view, and it also discriminates different learning paths for moving from
having no competences to the state of having all possible competences. In
accordance, a person’s level of knowledge, ability or proficiency is described, at
least theoretically, by exactly one competence state.
The structural model of the theory focuses on unobservable competences,
making hypotheses about the brain’s black box. By utilizing interpretation and
representation functions, these unobservable competences (or, in other words,
what is “in the brain”) are mapped to evidences or indicators, relevant for a
given domain. Such indicators can be all sorts of performance or behavior, and
not only test items. The interpretation function (p, in Figure 1) assigns a set
of competences required to solve a task to each of the indicators. Conversely,
by utilizing a representation function (q), a set of indicators is assigned to each
competence state. This assignment induces a performance structure, which
is the collection of all possible performance states. Due to these functions,
unobservable competences and observable performance can be linked in a broad
form where no one-to-one correspondence is required. This means that an entire
series of indicators can be linked to underlying competence states.
Figure 1: The CbKST model makes inferences about the brain’s competence state by means
of observable evidences.
CbKST accounts for the fact that indicators such as test items cannot be
perfect evidence for the latent knowledge or ability. There is always the possi-
bility that a person exhibits a correct behavior or activity just by chance. In
turn, a person might fail in a test item although the necessary knowledge or
ability is actually available. Because of this, CbKST considers indicators on a
probability-based level: mastering a test item suggests having the underlying
competences with a certain probability. Conceptually, this view constitutes a
6
probability distribution over the competence structure.
The CbKST service, which is based on the theory described above, pro-
vides a software for formative assessment methods that can be integrated into
learning activity sequences [39]. It has been applied, for example, to enable com-
petence assessment in a web-based system for medical training [40], and also in
the scope of the NEXT-TELL [41] and the ROLE [42] projects. It is part of
the ECAAD methodology (Evidence Centred Activity and Assessment Design),
specifically the ProNIFA tools (“probabilistic, non-invasive, formative, assess-
ment”). Details of its architecture, implementation and usage are described by
Nussbaumer, G¨utl and Albert [43]. The CbKST service is available in form
of the nextTRACK and the nextREALITY educational software packages pro-
vided by the NEXT-TELL project. The Compod services of the ROLE project,
which were used for this study, are research prototypes and are available online
[44].
In the next section, we describe an adaptive serious game that has incorpo-
rated the CbKST services by using a SOA-based approach.
5. The Journey
The Journey is a serious game to teach basic concepts of probability theory
to high school and entry-level university students, developed at the University of
Genoa as a prototype implementation of a service-based adaptive SG, employing
the CbKST service to implement basic adaptation features for learning. The
objective of this development was to create a proof of concept that can be further
developed later. In the game, the player represents the head of a group of hikers
who wants to reach the top of a mountain chain. There are many ways to get
there, so it is important to choose smartly to get to the end of the journey as
fast as possible. Players have to understand how to calculate the probabilities
of events that are related to the journey, and also use their knowledge to make
the best possible decisions along the way.
When the player starts the game, she is first introduced to the story and
the objective of the game. Next, the player reaches a point called a crossroad,
in which she must choose between two paths, each with different probabilities
of success and different lengths. The player has to calculate the probabilities
for each way (Figure 2), and based on the results, she has to choose which way
to go. If she calculates the probabilities correctly, the system decides, following
the probability distribution of that path, if the group managed to go through
the path or not. If the group was lucky enough, they move forward to the next
crossroad; if not, they have to go back and try the other path, losing time.
However, if the player calculates one or both probabilities wrongly, she is not
able to proceed. In that case, the game shows her the correct answers and takes
her back to the crossroad, presenting a new set of tasks. The process repeats
until the end of the game.
There are two goals in the game: one external, which is communicated to the
player, and one internal. The external goal is reaching the end of the journey
as fast as possible. The internal goal is acquiring all the competences in the
competence model (see Section 5.1), and this is the goal to be reached for the
game to end. The final score depends on how “fast” the player reaches the
end (in the game’s internal time measure; real world time is not taken into
consideration) and on the performance of the player in the tasks.
7
Figure 2: The Task screen of The Journey.
The prototype has been subjected to an early user test with 10 participants,
aiming to assess the game’s pedagogical value and usability. The results of the
evaluation of the learning effect were encouraging. In addition, no performance
issues were found; minor usability problems were identified and will be fixed in
future developments.
5.1. Learning and assessment
The competence model of the game is depicted in Table 1. For each com-
petence in the model there is a set of predefined tasks. See below one example
question, which refers to the competence “Probability space”. The values inside
the curly brackets are generated by the game.
Up to now, {n}people tried to take this path, but only {x}of
them managed to get through. Based on this sample, what is the
estimated probability of arriving at your destination through this
path?
The game provides guidance via the implementation of hints, offered to the
player after 3 minutes of inactivity when in the Task screen. The game shows
a graphical representation of the probability space and an explanation about
how to apply the formula. If the player answers the task incorrectly, the game
informs so and offers the correct answer and its explanation. The representation
of the competence model itself is not exposed to the player.
The assessment in the game is based on the player’s answers to the tasks,
providing the features of an adaptive learning environment. The answers are
8
ID Competence Description Dependencies
1 Probability
space
The learner understands the relationship of a
collection of events and their probability mea-
sure within a sample space (the representation
of all possible outcomes of the events) with
values ranging from 0 to 1 (where 0 means
impossibility and 1 means certainty of an out-
come). The learner is able to estimate the
probability of an event from data of observed
outcomes. The learner is able to derive that
P(¬A)=1P(A).
-
2 Probability of
mutually exclu-
sive events
The learner understands the relationship be-
tween two mutually exclusive events in the
same probability space, which can be rep-
resented by the formulas P(AB) = 0 and
P(AB) = P(A) + P(B)
1
3 Probability of
non-mutually
exclusive
events
The learner understands that when there
are two non-mutually exclusive events in
the same probability space (P(AB)6= 0),
they can be represented by the formulas
P(AB) = P(A) + P(B)P(AB).
1
4 Probability of
independent
events
The learner understands that the prob-
ability of two consecutive and indepen-
dent events is calculated using the formula
P(AB) = P(A)×P(B).
1
5 Probability
of dependent
events
The learner understands that the proba-
bility of two consecutive events is calcu-
lated differently when one of the events
is dependent on the other. In that
case, P(AB) = P(A)×P(B|A), and conse-
quently, P(B|A) = P(AB)/P (A) .
2, 3, 4
Table 1: The competences targeted by The Journey and their dependencies.
forwarded to the adaptive assessment module, which holds the domain model
and a representation of the competence state of the player. The service uses the
player’s answers to the tasks to update a model of the player’s competences,
and uses this information to send back to the game the ID of the next tasks
that are appropriate to the user’s level. The tasks are chosen randomly from
that set of tasks for the competence.
The game ends, that is, the group reaches the top of the mountain, once the
player has acquired all five competences.
5.2. Implementation architecture
The Journey has been developed following a Service Oriented Architecture
(SOA) approach. It was designed to run locally in a machine with a working in-
ternet connection, as the connection with the adaptation service is implemented
via network calls.
The game itself is a Flash Desktop Application running on Adobe Air. It is
connected to a local SQLite database, which holds the game’s tasks. The game
uses Starling, an ActionScript 3 2D framework [45], for the graphical interface.
The CbKST service is a REST-based web service. REST services have gen-
erally a better performance than SOAP (the other popular protocol for the
implementation of web services) due to their less verbose messages and because
there is no need for message wrapping and serializations [46]. The messages
exchanged with the service are basic XML files that contain very small amount
9
of data (in the case of The Journey, typically no more than 100 bytes), result-
ing in interaction time between the game and the service in the range of 50-150
milliseconds per request in typical usage conditions, and of 150-900 milliseconds
when simulating a 9.6 kbps connection.
The architecture features a very marked separation between game and the
adaptation service, with the game’s tasks and behaviors completely independent
from the service. The game’s interface with the service is well defined and has a
limited scope: the service receives information regarding task completion only,
and returns the list of competences acquired by the player and the suggestion
for the next task. The service has no knowledge of the tasks themselves, except
for the relationship between the tasks IDs and the competences in the model.
In addition, the service does not hold any profile information about the players
other than the learner ID, informed by the game when opening a learning session.
The game makes synchronous calls to service, which means that the game
waits for the server’s answer before continuing.
A simple, non-adaptive task sequencer class is included in the game, which
can work as a back-up solution whenever the CbKST service is not available,
making the game playable also offline. In this case, the sequence of tasks pre-
sented to the player is defined in a much simpler way: when the player responds
correctly to a task, the back-up task sequencer assumes that the competence has
been acquired and suggests, as next challenge, a task from the next competence
in the competence model.
Currently, as it is a prototype with limited availability, the CbKST service
is not registered in a service broker and can only be accessed by static binding,
i.e. the service interface and location have to be previously known and ac-
cessed directly. The service also has to be configured in advance with an XML
representation of the learning domain competence model.
A typical interaction between game and service would be as represented in
the Business Process Model Notation (BPMN) diagram in Figure 3:
1. The player starts the game. The game asks the service to open a game
adaptation session.
2. The service initializes the session, with default values for each competence.
3. The player reaches a decision point (crossroad). The game asks the service
for two tasks (or problems).
4. The service analyzes the current state of the competences of the player
and suggests the IDs of two tasks.
5. The game pulls the tasks from the database and presents them to the
player. The game sends the results of the tasks back to service.
6. The service updates the competence model of the player accordingly.
7. The player chooses among the two possible paths. The game decides if
the player managed to progress in the chosen path or not and returns the
result.
8. The game sends the player to the next crossroad and the process repeats.
9. When the player has achieved all the competences in the domain model,
the service returns the message that no further tasks need to be performed.
The game ends and the game adaptation session is closed.
Figure 4 depicts the whole system’s service architecture using a SoaML nota-
tion, in which it is possible to see how the components of the architecture work
10
Figure 3: Business Process Model Notation (BPMN) diagram of The Journey.
together. In the figure, there are two participants (“The Journey” and “CbKST
service”) and two services contracts that connect them (“Manage game adap-
tation session” and “Assess competences”). The connections between them
represent their roles in that contract: “CbKST service” is the session manager
and the assessment provider, while “The Journey” is the session requester and
assessment requester.
The Participant diagram (Figure 5) represents the inner architecture of the
participant “The Journey”. The main Game Controller class is connected to the
Service Connector class (the darker box in the figure), to the Database Connec-
tor and to the Internal Task Sequencer. The Service Connector implements the
interfaces defined in the service contracts and makes the calls to the service that
manages the game adaptation session and performs the competence assessment.
The Database Connector accesses the local repository of game tasks. When a
connection to the service is not available, the Game Controller makes the assess-
ment requests to the Internal Task Sequencer class, which, as explained earlier,
performs a simplified evaluation of the player’s competences and assumes the
role to tell the Game Controller which task sequence to show to the player.
Finally, the Game Controller also accesses a package containing the Screens of
the game; this package depends on a local copy of the Starling framework.
The CbKST service is a black-box component of which only the interfaces are
known to a SG developer. These two interfaces and the methods that the service
provides are depicted in the Service Interface diagram (Figure 6). Alternative
implementations could replace the CbKST service, as long as they implement
the same interfaces established in the service contract.
The source code of the game is available online [47].
6. Evaluation
We have conducted an Architecture Tradeoff Analysis Method (ATAM) anal-
ysis in order to identify possible points for improvements, from the architectural
11
Figure 4: A SoaML Service Architecture diagram representing how the game component and
the CbKST service work together in the system architecture.
Figure 5: A SoaML Participant Diagram depicting the inner architecture of the game com-
ponent.
12
Figure 6: A SoaML Service Interface diagram displaying the two main interfaces of the CbKST
service that are used in the implementation of The Journey.
point of view. ATAM is a scenario-based method for assessing the quality of
system architectures, which provides a structured way to identify risks, sensi-
tivity points, and tradeoff points in the system. It was chosen for its ability
to assess if the architecture of the system is in fact capable of delivering the
desired quality attributes and fulfilling the software’s business goals. In addi-
tion, ATAM is especially suited for evaluating systems in relatively early design
stages and prototypes, serving as a valuable way for discovering weak spots that
can be addressed in subsequent iterations of the development [48]. ATAM has
been successfully used before to evaluate a game-based architecture, providing
useful information to the developers [49].
The ATAM analysis is typically carried out in two phases. The first phase
is architect-centric and focuses on describing and analyzing architectural docu-
ments, using scenarios to help determine if the architecture meets the desired
functional requirements. The second phase congregates a more diverse group
of stakeholders, including non-technical participants, to discuss and verify the
results of the first phase [50].
This section summarizes the results of the ATAM analyses carried out with
the prototype version of The Journey presented in this paper. The analysis
focused mainly on the first phase (architect-centric), due to the small number
of stakeholders involved.
6.1. Business drivers, quality attributes and scenarios
The main business drivers of the development of The Journey following a
SOA paradigm were: (1) to be able to reuse the algorithm for in-game adaptive
features for learning, in order to take advantage of existing services to make SG
development cheaper, faster and more efficient; (2) to give freedom to the SG
designer, providing the ability to easily incorporate various kinds of tasks in the
game (e.g. questions and answers, item collection, dialog with characters) while
maintaining in-game adaptation; (3) to have the possibility of supporting in the
future the use of shared user profiles across different games or learning tools.
13
Attributes Scenarios
Performance The player’s gaming experience is not affected by the software re-
sponse times
Availability The game can be played in case an internet connection and/or the
service is unavailable
Modifiability
The game can be modified to include different task types (e.g. Q&A
tasks, item collection, item sorting, dialog with characters, etc.)
The game can be expanded to include other features (different input
methods, teacher assessment interface, etc.)
Related games can be created on the same learning domain
Related learning tools (games or otherwise) can be created, sharing
the same user profile
Table 2: The attributes and scenarios used during the ATAM evaluation of The Journey.
Based on the business objectives above, three main quality attributes were
classified as high priority: performance during runtime, availability and modifia-
bility. Table 2 represents the scenarios used to evaluate each of these attributes.
6.2. Risks, non-risks, sensitivity points and tradeoff points
From the direct comparison between the quality attributes and scenarios
listed in Section 6.1 and the architectural approaches described in Section 5.2, a
number of risks, non-risks, sensitivity points and tradeoff points were identified
and grouped according to their general themes.
From the viewpoint of the game performance, the analysis indicated that
network latency problems are unlikely to happen due to the small size of the
XML messages exchanged, and response times obtained in performance tests are
low enough not to disturb the game flow. It has been added that, even so, the
game could implement workarounds to minimize the risk even more, by using
animations or adding other activities relevant to the game while it is waiting for
the response from the server. The use of synchronous calls, although carrying
the risk of delaying the game while waiting for the service response, increases
the system reliability, as it ensures that the in-game adaptation behaves as
expected.
It has been considered that the availability of the game is satisfactorily
addressed, as the game has an internal task sequencer that is able to substitute
the CbKST service when the service or a network connection is not available.
There is still an associated risk, given that, if the connection fails permanently in
the middle of the game, the current system has no way of reacting and switching
to the internal module on the fly. This scenario has been considered unlikely;
nevertheless, future versions of the software should address the risk by making
it possible to switch between the two task sequencers in a dynamic and reliable
way.
The modifiability of the system, particularly the possibility for future ex-
pansions, has also been positively assessed, although in this attribute there are
some tradeoff points that need to be taken into consideration. The competence-
based assessment is a robust, well-grounded and scientifically sound method for
evaluating the player’s performance, which is seen as sufficient for a wide variety
of SGs. With the simple, limited scope interface offered by the CbKST service,
a lot of flexibility is given to the game developer it would even be possible to
delegate the assessment to another service outside of the game, e.g. following
an evaluation framework structure suggested by Serrano et al [51]. However,
14
before including other types of task in the game, it is necessary to adapt their
behavior to fit the atomic-competences model supported by the CbKST, e.g.
by including a “translator” module able to connect the new types of tasks to
the existing competence-based task assessment model. In addition, other types
of assessment and adaptation (e.g. assessment of entertainment or of emotional
states) are not yet supported and would require extra care to ensure that the
different adaptation services would work well and consistently when combined.
The possibility of sharing the same user profile across different games or
other learning tools may be obtained through a third component, a user profile
manager service, that would ensure that different tools could access the same
user profile without the risk of unpredictable results when two or more learning
tools try to update the same profile at once.
Finally, a temporary risk identified is the fact that the binding between the
game and the service is static due to the limited availability of the prototypes.
Consequently, any changes in configuration have to be made manually. Further-
more, it is not currently possible to choose alternative services at runtime. This
is, however, a temporary limitation that will be fixed in future developments.
7. Discussion
Using our experience in the development of The Journey and the subsequent
ATAM evaluation of the architecture, we argue that the application of SOA in
the development of serious games can result in shorter development times, and
more focus and flexibility in the development. While the conclusions drawn in
the ATAM analysis are directed to this specific case study, in this discussion we
extrapolate these conclusions to consider also the applicability of SOA to SG
development in general.
In the ATAM analysis, we confirmed the ability of the service-based archi-
tectural approach to fulfill the desired objectives (i.e. business goals), namely
modifiability, availability and performance, in addition to modularity and flex-
ibility in SG development, as already discussed in Section 6.2.
Regarding the objectives that concern quality attributes related to the per-
formance of The Journey, we concluded that the current implementation of the
game is able to cope with the demands in typical usage situations. Nevertheless,
the ATAM analysis helped identify possible improvements that would increase
the overall quality and robustness of the system, especially related to the perfor-
mance of the game in case of unexpected network/service unavailability, failure
or slowdowns.
The ATAM analysis also allowed us to identify sensitivity points and trade-
offs that deserve extra attention. The issues identified in the analysis were
particularly significant for the scenarios of future development of more com-
plex SGs (i.e. games that incorporate different types of tasks or that adapt
to other characteristics or states of the player) or richer learning environments
that incorporate shared user profiles. In these cases, the current architecture is
a good starting point for the development, but these environments would still
require a non-trivial amount of work to ensure the smooth functioning of all the
components.
Concerning general aspects of the use of SOA in SG development, we consider
that the most immediate benefit is the possibility to reuse services, as it directly
15
impacts the development times and the ability of the development team to focus
their efforts in other aspects of game development (graphics, questions, game
flow, etc.). In the case of The Journey, we could utilize the CbKST service
the result of intense research and development work of experts in the field of
adaptation technologies with a relatively small impact in development time.
In addition to the specific issues identified during the ATAM analysis, a
few other general considerations must be taken into account when applying the
SOA approach for SG design. First of all, the programming paradigm change
requires adaptations in the style of development. Testing becomes even more
crucial and at the same time more complicated, as the binding of services can
produce unexpected results, causing errors and bugs that are harder to track.
The quality of documentation is even more important in a SOA approach
than in traditional software engineering methods, as SOA assumes little or no
communication between development teams, relying completely in the definition
of the interfaces for the integration between the pieces of software. This is the
reason why efforts such as the Serious Games Services Catalog are so valuable, so
that documentation and examples of code are easily accessible to the developers.
Another issue with the SOA approach is the usability of the service itself,
especially in cases where the service must be configured in advance. Often such
customizations are made via configuration files, and in this case, the lack of
administration user interfaces may prove to be problematic to the use of the
service by third parties. Once again, good documentation is crucial.
8. Conclusion
In this paper we have discussed the benefits of adaptive features in SGs and
defended the Service Oriented Architecture approach as a solution to make it
easier for developers to enhance their SGs by incorporating existing services in
their games with small overhead and added benefits. While there are many
examples of games using services (e.g. casual games in social networks), in this
work we focus on the use of services created specifically for educational SGs.
We described the concepts, structure, software implementation and evaluation
of The Journey, a serious game to teach probability to high school and entry-
level university students, which employs the SOA approach and utilizes a service
based on the Competence-based Knowledge Space Theory (CbKST) to imple-
ment in-game adaptation for learning. Unlike existing examples of SOA-based
SGs (e.g. Rashi Intelligent Tutoring System), in which all components were
built by the same team, the development process of the CbKST service was
completely independent of that of The Journey. Furthermore, the adaptation
features provided by the CbKST service are generic and can be utilized in a
variety of learning settings, game-based or not.
Based on our experience, we argue that the SOA approach is able to pro-
vide SG developers with significant benefits, particularly increased flexibility
and shorter development time. It is also relevant to mention that, by using
service-based components, the developer has access to quality, always up-to-
date components, created and maintained by experts in the field, and being
exploited and tested by a variety of users. The SG developer may thus better
focus on specific features and pedagogical aspects of the game itself.
Our work in The Journey is a prototype implementation of the SOA ap-
proach to SG development. We prioritized the deployment of adaptation for
16
learning as it is an important and non-trivial feature for SGs, whose implemen-
tation from scratch would require prior knowledge on the theory of competence-
centered assessment. We hope to have demonstrated how this complex theory
can essentially be treated as a black box service that allows for easy addition of
adaptive features in a SG.
The game’s current implementation is a starting point that can be extended
in several directions, exploiting the SOA paradigm. One possible development
is the use of stealth assessment [8, 38, 52] to detect behaviors in the game,
which can be mapped to competences in the competence domain. Another
improvement involves exposing the competence model to teachers via an as-
sessment interface or even to the players themselves, thus incorporating other
pedagogical practices (e.g. self-reflection and formative feedback) to the existing
game mechanics [53]. Moreover, other games could access the same competence
model, as SOA enables sharing user profiles across different games. This paves
the way to a richer learning environment, in which games can adapt according to
achievements obtained in any one of the connected learning technologies. Using
the Architecture Tradeoff Analysis Method (ATAM) evaluation of the architec-
ture, we have discussed how these and other future developments would affect
the current architecture and which risks and sensitivity points would require
extra attention.
Furthermore, currently only one feature of the game is deployed as a service.
The SOA paradigm allows for the development of services implementing other
generic, game- and domain-independent features such as user profiles, knowl-
edge databases, dialog services, etc. Ultimately, the objective is to have a whole
ecosystem of generic services that support cheaper and more efficient develop-
ment of SGs, with dynamically bound services that would allow for much more
flexibility in the development.
With this work, we hope to encourage a wider adoption of the SOA approach
to SG development, as we believe that it makes it possible for developers to
produce higher quality and feature rich games with relatively low effort.
Acknowledgements
This work has been partially funded by the EC, through the GALA EU Net-
work of Excellence in Serious Games (FP7-ICT-2009-5-258169). This work was
supported in part by the Erasmus Mundus Joint Doctorate in Interactive and
Cognitive Environments, which is funded by the EACEA Agency of the Euro-
pean Commission under EMJD ICE FPA n 2010-0012. This work is partially
supported by the European Commission (EC) under the Information Society
Technology priority of the 7th Framework Programme for Research and Devel-
opment under contract no 258114 NEXT-TELL.
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Thesis
This thesis presents the development of a mobile robot, called Ludibot, based on the Kinect v2 sensor and designed from a multidisciplinary perspective. It is a prototype that allows the development of ludo-educational applications for language learning purposes, from human-machine gesture interaction. The main contribution of this thesis is the unusual combination of mobile robotics, the language and culture teaching, and game science from theory and practice. From theory, chapter 1 presents a multidisciplinary theoretical and conceptual framework that bets on the knowledge construction by the learner from his own experience of human-machine interaction, aiming an attractive, meaningful, and effective learning. From practice, chapter 2 exposes the object-integrated architecture from which two ludo-educational prototypes were designed, built, and tested to complement and facilitate the language teaching and learning through the use of technology. In the same chapter, the properties, the relationships, and the behaviors are explored, that together give the ludo-educational character, and the first two versions of a ludo-educational robot with a graphical interface, a state machine, multimodal actions, and control strategies are discussed in details. Finally, chapter 3 introduces the applications developed during the project for both versions of Ludibot, and the opened prospects by the investigation are discussed. In addition, this work is oriented to the search of a novel human/machine interaction functional, easy to use, and open to mechanisms and contents personalization, according to varied contexts for playful language learning.
... The difficulty of the trial could increase in terms of environment noise (e.g., environmental noise and/or overlapping voices by specific "competing" NPCs), length and meaning of NPC messages. This could be implemented as a service, in a service oriented architecture perspective (e.g., [46]), or even a game engine plug-in [47], and supported through an authoring tool for efficient development. ...
Chapter
Auditory attention is fundamental also in serious games. This paper synthetizes the results of a recent statistical analysis of auditory attention of non-native learners and proposes indications for serious game design. We propose a 3-dimensional difficulty level model that can be applied both for designing game levels and adaptivity to keep a player in the flow. The model suggests using background noise level as a prime factor to increase the difficulty of the game, followed by the length of the stimulus and the semantic complexity of the message. We also propose the concept of a mini-game format specifically aimed at training auditory attention and performance. As a format, it could be easily customized in different context domains and implemented as a service or a game engine plug-in.
... Recent research in the field of Serious Games is conducted on architecture that is oriented entirely towards services [4,3]. Service-Oriented Architecture (SOA) is a set of practices for architectural design of software that exploits services as loosely coupled components orchestrated to deliver various functionalities. ...
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In this paper we demonstrate how to integrate 3rd party services in serious games. We use message queue broker and micro-services in a publish/subscribe manner in order to use real-time 3rd party data into a serious game’s logic. First, we discuss the benefits of service-oriented architecture. Then, we analyze and compare different message queues brokers in terms of data latency, throughput, fail-tolerance and scalability for the purpose of serious games. As a sequence, we apply those best practices from other domains in the field of Serious Games (SGs). Finally, we summarize the presented ideas and comparisons and draw conclusions.
... Some other authors have worked on a particular part of the 3-way decomposition mentioned above. For instance, recent research is conducted on architecture that is oriented entirely towards services (Carvalho et al., 2014), (Carvalho et al., 2015). Service-Oriented Architecture (SOA) is a set of practices for architectural design of software that exploits services as loosely coupled components orchestrated to deliver various functionalities. ...
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Serious games (SG) allow us to learn even when we are relaxing. These games are called “serious” because they allow us to be trained at domain-specific knowledge level. That is the main reason SG are gathering an even increasing research interest in recent years. In contrast with traditional, purely entertainment games, SGs architectures and design principles are under active investigation by researchers. Recent work in that field attempts to define how SG are structured, built, used and extended. However, there is still a lot of debate which design techniques are adequate or which techniques can be borrowed from other fields – such as computer science or mainstream entertainment games. The main objective of our research is three-fold: investigate and analyze current architectural approaches; summarize the top characteristics of a modern serious game; and propose an architecture that is coherent with current approaches. Following these principles, we determine that the prevailing views in the SGs area are that they should be distributed and modular, service-based and easily extendible. Building on top of that, we come up with a novel concept for creating serous games that are independent of their input devices and propose two ways that independence can be achieved. We briefly discuss the possible integration of 3-rd party services by using message queue brokers in a publish / subscribe manner. Finally, we summarize and propose different methods for extending our proposed approach.
... Una de las arquitecturas planteadas para el desarrollo de juegos serios en Android es aquella orientada a servicios, la cual es un conjunto de prácticas para el diseño de la arquitectura de software que aprovecha los servicios como componentes de forma flexible para entregar diversas funcionalidades [8]; también se tiene la metodología aose, cuyo propósito es la creación de herramientas que permitan el desarrollo económico y mantenimiento de software basado en agentes [9]. Los modelos basados en agentes establecen una nueva generación de técnicas computacionales, que permiten ajustar la estructura de un sistema complejo y simular su evolución a lo largo del tiempo [10]. ...
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Introduction: This article derives from the research project on the “state of the art of serious games on Android mobile platform for learning software modeling”, conducted by the software development incubator at the Instituto Tecnológico Metropolitano between 2015 and 2017. The objective of the research was to look for serious games on Android for learning software modeling. Methodology: A search was made in digital databases, such as Scopus, ebsco, Elsevier, ieee Xplore, Digital Library, among others. The search was focused on the development of serious games on Android for learning software modeling. Results: Fifty-two articles were found that met the research guidelines, but not its objective. In addition, great benefits of using mobile devices as a tool in education were identified. Conclusion: It was found that serious games are a very important tool in the learning process, but as their use is not massive or, for now, they have not been implemented in all fields of knowledge, the teacher must be committed to assisting students as they adapt to their use.
... In the future, Service oriented architecture (SOA) would be a choice for the architecture game implementation. The access of the game is not preoccupied on the amount of memory required to play the game, but would be more on the speed of access to play the game [13]. Moreover, all facilities and controls in the game are provided by a server that can be accessed by multiplayer. ...
Conference Paper
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Computer games become a common thing and provide many forms for different stages of age. However, today people argue that those games bring adverse effect on children by exposing hostile characters and violence. On the contrary, such games are utilized as a tool that makes the users enjoy their fun activities. Nowadays, computer games are not only for entertainment purposes. It can be observed from the rapid development of serious games that can be used for serious purposes such as education, simulation, health research, and therapy. The examples of serious games include game designed for cognitive disorders for relaxation therapy during painful medical treatments, e.g., for the cancer chemotherapy patients and games based on assessment/observation psychological scenario with some therapeutic purposes and focused on the problem of pre-school children. Those serious games are intended to help professionals as well as to enable users to enjoy themselves through straightforward, real interaction while learning how to cope with several real social situations. This paper explained and discussed the benefits of serious games based on the technology review of some related researches. It found out that serious games can be a reliable and effective tool when they are used as a method for social benefit and medical benefit.
Chapter
Reality-enhanced serious games (RESGs) incorporate data from the real world to enact training in the wild. This – with the proper cautions due to safety - can be done also for daily activities, such as driving. We have developed two modules that may be integrated as field user performance evaluators in third-party RESGs, aimed at improving driver’s fuel efficiency. They exploit vehicular signals (throttle position, engine revolutions per minute and car speed), which are easily accessible through the common On-Board Diagnostics-II (OBD-II) interface. The first module detects inefficient and risky driving manoeuvres while driving, in order to suggest improvement actions based upon fuzzy rules, derived from analyzing naturalistic driving data. The second module provides an eco-driving categorization for a drive via two indicators, fuel efficiency and throttle position values. The estimation of fuel efficiency for the whole trip relies on the mentioned signals, plus the OBD-II calculated engine load. Data from ‘enviroCar’ project’s, a naturalistic driving archive, was used in a simulation. The results are promising in terms of accuracy and encourage further steps towards more effective modules to support a better driving performance, for RESGs.
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Learning in games has historically been assessed indirectly and/or in a post hoc manner. What’s needed instead is real-time assessment and support of learning based on the dynamic needs of players. We need to be able to experimentally determine the degree to which games can support learning, and how and why they achieve this objective. In this chapter we describe an approach to designing and developing evidence-based diagnostic assessments that may be embedded in a game environment. When embedded assessments are so seamlessly woven into the game that they’re virtually invisible, we call this “stealth assessment.” Embedding assessments within games provides a way to monitor a player’s current level on valued competencies, and then use that information as the basis for support, such as adjusting the difficulty level of challenges or providing a report for the teacher.
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Serious games as learning medium have advanced in the past few years. They have been applied to support learning in various fields such as security, health-care, and education. Serious games can scale from low budget games up to high budget games depends on the games' objectives and features. For instance, military may utilize games with 3D simulation, live characters, and extensive scenario for combat training due to its critical mission. Nonetheless, in a classroom or remote set-up learning environment, most of these high level games are impractical to be adopted due to the amount of costs they may induce. This is most of the case in educational games which main objective is to motivate the student to learn. However, a game development remains as a time consuming, complex, and laborious process. In order to simplify and shorten this process, it is highly attractive to create a platform to produce educational games. Therefore, this paper, based on our previous work, proposes a platform for authoring HTML5 serious games intended in particular, but not limited to create lightweight serious games for educational purpose using the upcoming HTML5 standard playable in common web browsers. This platform, puzzle-it, divides the work of game development into two distinct layers i.e. contents authoring and core engine development. Both readily and work in progress components of the platform are presented and discussed.
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Serious games present a promising opportunity for learning, but the genre still lacks methodologies and tools for efficient and low-cost production, particularly for teacher and domain experts. This article gives an authoring framework that aims to provide structured support, from content design to final implementation. In particular, we have abstracted a conceptual model—the SandBox Serious Game - which relies on a generalization of task-based learning theory. The model invites players to perform cognitive tasks contextually while exploring information-rich virtual environments. We consider it particularly suited for cultural heritage entertainment applications. The model defines games that are set in realistic virtual worlds enriched with embedded educational tasks, which we have implemented as minigames. This approach simplifies the authoring work, which can easily be supported by visual authoring tools for ontology-based urban 3D modeling and implementation tasks, thus allowing an approach similar to the mind-maps concept. We propose a top-down methodology for content preparation, starting from a city-level analysis down to the single points of interest and associated tasks, which are instances of simple predefined minigame/quiz typologies. We provide examples and discuss criteria for selecting task typologies according to the authors' cognitive targets. Finally, we discuss the results of a user test, which took place in a lab, aimed at verifying the acquisition of cultural heritage knowledge in a pleasant and engaging way. Games appear particularly suited for supporting the study of images, especially of iconography. Compared to reading text, a game forces the player to focus more strongly on problems, which favors knowledge acquisition and retention. Learning complex concepts requires an investigative attitude, which can be spurred by well-designed games. Good design involves usability, graphic appeal, appropriate content, and the presence of connections which a player must discover in the content. Players should be asked to pay attention to and reason about their whole game activity - including the relationships between the game content, the brief introduction, and concluding texts. More comprehensive tests are needed to better investigate the educational effectiveness—however, the first results are promising, especially in terms of user motivation and creation of new opportunities for learning about CH.
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Although there is a consensus on the instructional potential of Serious Games (SGs), there is still a lack of methodologies and tools not only for design but also to support analysis and assessment. Filling this gap is one of the main aims of the Games and Learning Alliance (http://www.galanoe.eu) European Network of Excellence on Serious Games, which has a focus upon pedagogy-driven SGs. This paper relies on the assumption that the fundamental aspect of SG design consists in the translation of learning goals/practices into mechanical element of gameplay, serving to an instructional purpose beside that of play and fun. This paper proposes the Learning Mechanics–Game Mechanics (LM-GM) model, which supports SG analysis and design by allowing reflection on the various pedagogical and game elements in an SG. The LM-GM model includes a set of pre-defined game mechanics and pedagogical elements that we have abstracted from literature on game studies and learning theories. Designers and analysts can exploit these mechanics to draw the LM-GM map for a game, so as to identify and highlight its main pedagogical and entertainment features, and their interrelations. The tool may also be useful for teachers to evaluate the effectiveness of a given game and better understand how to implement it in educational settings. A case study is reported to illustrate the framework's support in determining how gameplay and pedagogy intertwine in an SG. Finally, the paper presents the results of two comparative user tests demonstrating the advantages of the proposed model with respect to a similar state-of-the-art framework.
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There is a consensus that serious games have a significant potential as a tool for instruction. However, their effectiveness in terms of learning outcomes is still understudied mainly due to the complexity involved in assessing intangible measures. A systematic approach—based on established principles and guidelines—is necessary to enhance the design of serious games, and many studies lack a rigorous assessment. An important aspect in the evaluation of serious games, like other educational tools, is user performance assessment. This is an important area of exploration because serious games are intended to evaluate the learning progress as well as the outcomes. This also emphasizes the importance of providing appropriate feedback to the player. Moreover, performance assessment enables adaptivity and personalization to meet individual needs in various aspects, such as learning styles, information provision rates, feedback, and so forth. This paper first reviews related literature regarding the educational effectiveness of serious games. It then discusses how to assess the learning impact of serious games and methods for competence and skill assessment. Finally, it suggests two major directions for future research: characterization of the player’s activity and better integration of assessment in games.
Article
A key factor for the success and efficacy of an educational medium is the extent to which it is capable of addressing the preferences, abilities, strengths, weaknesses, and goals of individual learners. Research in the field of learning and instruction has demonstrated in the past that one on one tutoring is the most effective and powerful way of teaching. Ever since, the research community attempted to equip artificial systems with the strength and abilities of human tutors. Specifically in a medium such as educational computer games an appropriate personalization is a key factor for fun, immersion, and ultimately learning. The same holds true for serious, in particular educational, games. Because the key strength of serious games is seen in their intrinsic motivational potential, it's all about focusing on the learners. More importantly, in contrast to conventional educational systems, in games this means accounting for both, a game related and a learning related hemisphere. This report attempts to emphasize the importance of advancing a construct such "educational game AI" and it illustrates recent technologies and approaches.