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<article xmlns:xlink="http://www.w3.org/1999/xlink">
  <front>
    <journal-meta>
      <journal-title-group>
        <journal-title>A. Maté, J. Trujillo, Tracing conceptual models' evolution in data warehouses by using
the model driven architecture, Computer Standards and Interfaces</journal-title>
      </journal-title-group>
      <issn pub-type="ppub">1613-0073</issn>
    </journal-meta>
    <article-meta>
      <article-id pub-id-type="doi">10.4236/ijcns.2023.165005</article-id>
      <title-group>
        <article-title>modeling approach for designing explainable Artificial Intelligence</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Álvaro Navarro</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff1">1</xref>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Ana Lavalle</string-name>
          <email>alavalle@dlsi.ua.es</email>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff1">1</xref>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Alejandro Maté</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff1">1</xref>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Juan Trujillo</string-name>
          <email>jtrujillo@dlsi.ua.es</email>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff1">1</xref>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <contrib contrib-type="editor">
          <string-name>EXplainable Artificial Intelligence, Conceptual Modeling, Attention-Deficit/Hyperactivity Disorder</string-name>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Lucentia Research Group, Department of Software and Computing Systems, University of Alicante</institution>
          ,
          <addr-line>Carretera San</addr-line>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>Project Exhibitions</institution>
          ,
          <addr-line>Posters and Demos, and Doctoral Consortium</addr-line>
        </aff>
        <aff id="aff2">
          <label>2</label>
          <institution>Vicente del Raspeig s/n, San Vicente del Raspeig</institution>
          ,
          <addr-line>03690, Alicante</addr-line>
          ,
          <country country="ES">Spain</country>
        </aff>
      </contrib-group>
      <pub-date>
        <year>2022</year>
      </pub-date>
      <volume>36</volume>
      <issue>2014</issue>
      <fpage>831</fpage>
      <lpage>843</lpage>
      <abstract>
        <p>EXplainable Artificial Intelligence (XAI) has become one of the most important and complex issues to address in the current Artificial Intelligence (AI) field. This topic is the key point to foster the adoption of the AI solutions, providing reliability in the AI systems. There are multiple XAI techniques, with its own characteristics such as the technical level or confidence required to make use of them. In this context, modeling approaches can aid in managing the complexity and describe the implementation alternatives available. However, there is a lack of these modeling approaches that help the XAI developers to select and apply the most adequate XAI techniques in the specific scenarios. Motivated by this issue, we aim to present a modeling approach to support XAI developers in the XAI processes. Then, we propose a conceptual model, which is represented in a Unified Modeling Language (UML) class diagram, to capture the key XAI elements. The main advantage of our proposed conceptual model is that it takes into consideration: (i) how the explanations should be generated; (ii) how these explanations will be combined and supported; and (iii) what explainable interfaces, where these explanations are included, will be generated and presented to the end-users. Finally, to test the applicability of our proposal, we have exemplified it through a real project focused on diagnosing the Attention-Deficit/Hyperactivity ER2023: Companion Proceedings of the 42nd International Conference on Conceptual Modeling: ER Forum, 7th SCME, ∗Corresponding author.</p>
      </abstract>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>-</title>
      <p>CEUR
ceur-ws.org</p>
    </sec>
    <sec id="sec-2">
      <title>1. Introduction</title>
      <p>
        Currently, our society heavily depends on Artificial Intelligence (AI) systems [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ]. Moreover, the
industry 4.0 aims to increase it, improving the citizens’ everyday life through these systems,
which encompass Machine Learning (ML) and Deep Learning (DL) models. These systems and
models learn and execute diferent tasks in diferent areas such as medical diagnosis [
      </p>
      <sec id="sec-2-1">
        <title>2] or flood</title>
        <p>forecasting [3]. Nonetheless, many of these systems are opaque, i.e., it is dificult to understand
the reasons behind the decisions that have been made by them.</p>
        <p>This opacity prevents end-users from making use of their right to have explainable systems</p>
        <p>CEUR
Workshop
Proceedings
htp:/ceur-ws.org
ISN1613-073</p>
        <p>CEUR Workshop Proceedings (CEUR-WS.org)
according to the European AI perspective [4], where it is argued that the AI systems must
be understandable and explain how have reached their decisions. Moreover, this black-box
nature can also lead these systems to make unfair decisions before being detected. For example,
there have been AI systems that have developed a discriminatory behaviour toward some
races (In [5], an AI system was used by judges to decide if a person is kept in prison or not)
or genders (In [6] an AI system from Amazon to qualify job applicants was skewed against
women). Both above-presented points emphasize the relevance of understanding the AI systems
decision-making processes before reaching society.</p>
        <p>Given this demand for interpretable and understandable systems, eXplainable Artificial
Intelligence (XAI) emerged to address the lack of information in AI systems, as a key aspect
in the integration of AI in diferent domains. In this context, XAI aims to provide additional
information for the opaque models in their current state. On the one hand, it allows ML
developers (henceforth referred to as ML experts) to develop ML and DL models, which are
subsets of the AI systems, in a better way. This is possible by verifying that these models are
free from inconsistencies, errors, and skewed behaviours. On the other hand, it allows end-users
to (i) understand the output of the models, (ii) trust in the rationale or rules learned by the
models, and (iii) have confidence on the decisions made by these models.</p>
        <p>However, applying explainability techniques is a dificult task to be achieved. First, the most
correct XAI techniques vary depending on diferent dimensions involved in the case study,
which creates a complex scenario that needs to be deeply analyzed. Second, there is a lack of
conceptual models to help XAI developers/designers (henceforth referred to as XAI experts)
to be capable of applying XAI techniques to diferent AI systems to generate the necessary
explanations.</p>
        <p>In such a complex scenario, although explainable approaches are being generated in diferent
AI scenarios, they are not providing end-users with the information to build trust through
explainable interfaces [7].</p>
        <p>Consequently, the XAI processes heavily depend on XAI experts to (i) analyse the scenario,
(ii) interpret the key elements in the specific case study, and (iii) translate the applied XAI
techniques in an explainable interface.</p>
        <p>In the context of XAI, these problems could be solved. Specifically, it is possible to solve them
by creating a conceptual model that allows to specify all the XAI points and analyse what is the
most appropriate explainable techniques and representation in each case study.</p>
        <p>Therefore, it is essential to provide XAI experts with tools that, together with their XAI
expertise, allow them to design and analyze XAI solutions to be implemented, so that users
obtain the right explanations for the specific AI contexts where XAI will be incorporated.</p>
        <p>Nevertheless, to define this conceptual model is far from trivial. In order to achieve it and guide
the XAI processes, there are diferent dimensions that should be included. Moreover, several
XAI State-Of-The-Art (SOTA) works (e.g., [8]) have emphasized that explanations can support
explanations, which permits to help end-users by generating more complete and understandable
explainable interfaces [7]. Apart from this, in the XAI SOTA, there are being discussed many
points that are not yet so clear, which presents a novel and partly-unexplored field that should
be mapped by proposals that help to understand the contexts of application of XAI.</p>
        <p>Motivated by this, we aim to provide a modeling approach that achieve these points. Thus,
we propose a conceptual model represented in a Unified Modeling Language (UML) [ 9] class
diagram that aids XAI experts in designing XAI systems, which captures the key elements in
the XAI field. Thanks to this, it is possible to draw the steps to achieve the most adequate
explanations adapting them to the specific case studies, which will be presented below.</p>
        <p>First, our proposed conceptual model captures the diferent kinds of explanations to be
generated. Second, it captures how these explanations will be combined and supported to
present a complete explainable interface to end-users. Finally, this conceptual model takes into
consideration how to design the explainable interface, where the diferent explanations will be
included [7].</p>
        <p>The rest of the paper is structured as follows. Section 2 presents the main concepts of XAI and
UML that are included in this paper. Section 3 presents the related works in the area. Section 4
presents the proposed conceptual model for XAI. The case study where our proposal has been
applied is presented in Section 5. Finally, the conclusions and the future work are presented in
Section 6.</p>
      </sec>
    </sec>
    <sec id="sec-3">
      <title>2. Background</title>
      <p>As previously-argued, many of the current AI systems present a lack of transparency and
interpretability, the relevance of XAI in the current AI field is clear. In this way, we will
summarize the key XAI concepts to the adequate understanding of our proposal. Moreover,
since our proposal is represented in an UML class diagram, the UML key concepts will be also
presented. Hence, both XAI and UML main concepts will be presented, as follows.</p>
      <p>First, there is presented a clear distinction among diferent models in the XAI field. This
dichotomy is widely accepted as a classification between transparent models, which present an
enough degree of interpretability, and opaque models (also categorized such as model-agnostic
or model-agnostic), where we should apply XAI techniques to understand their decision-making
processes [8].</p>
      <p>Second, an XAI technique is categorized depending on its scope, its methodology, and its usage
[10]. In the context of the usage categories, there are intrinsic techniques, which aim to decode
specific models, and post-hoc techniques, which aim to understand the logic behind agnostic
models. Specifically, there are diferent post-hoc techniques defined [ 8]: (i) simplification
techniques, which aim to create a more simple and understandable model that presents a similar
performance than the original; (ii) text techniques, which tackle the explainability by giving
information information abut the learning model process; (iii) visual techniques, which aim at
observing the model’s behavior through visualizations; (iv) local techniques, which segment
the solution space and give explanations that are relevant for the whole model; (v) feature
relevance techniques, which aim to extract the most relevant features that the model have
taken into consideration to make its decisions and weights these features; and (vi) example
explanation techniques, which are based on the extraction of data examples which refer to
the output generated by the model that should be explained. Moreover, it is possible to define
custom explanations by building new techniques and combine diferent techniques to present a
more complete explanation.</p>
      <p>Third, there is emphasized the relevance of identifying the diferent end-users in XAI. Thus,
it is possible to adapt the explainable interface, where the selected explanations will be included,
for them in the specific case study [ 7],</p>
      <p>Finally, as our proposal is represented in an UML class diagram, we will describe the main
concepts of UML that we have included in this paper. On the one hand, an UML class provides
information to create objects and contains their attributes, an UML abstract class plays a role of
superclass but can not be instantiated, and an UML enumeration that represents the possible
value of an attribute in a fixed set of discrete values. On the other hand, the UML association
denotes the relationship between diferent UML classes in a unidirectional or bidirectional way,
the UML composition is a stronger relationship where an object of one class contains another
class (if the container object is destroyed, the contained objects are also destroyed), and the
UML generalization that represents the inheritance between classes where a subclass inherits
attributes and operations from a superclass.</p>
      <p>Once presented these XAI and UML concepts, we are able to present the related work in the
XAI area, our proposal, and the case study where it has been applied, as follows.</p>
    </sec>
    <sec id="sec-4">
      <title>3. Related work</title>
      <p>In this section, we will discus (i) how XAI is being applied in the AI field, (ii) the diferent
possibilities to model XAI, and (iii) how our proposal supports XAI in its current state by
bridging the gap between the XAI and modeling fields, as follows.</p>
      <p>As argued in [8], the XAI applications, which are being applied in diferent domains ( e.g.,
healthcare [11]), directly depend on the DL or ML models which the explanations are based on.
In this context, there are diferent frameworks focused on applying XAI in Natural Language
Processing [12], Reinforcement Learning [13], or even in analysing the existing goals, metrics
and users to reveal the necessity of making an efort to drive the design and implementation of
XAI [7].</p>
      <p>Analyzing the modeling field, we have taken into consideration diferent techniques. On
the one hand, the i-star framework [14] has been applied in diferent contexts such as ML
[15]. Hence, it could help to extract the XAI requirements in AI scenarios. On the other hand,
diferent Object Constraint Language (OCL) rules [ 16] have been defined in diferent case studies
(e.g., Data Warehouses [17] or Visualizations [18]). However, as this paper aims to cover all XAI
key elements in a Platform Independent Model, the above-presented techniques are out of this
paper scope. Finally, a recent work studied the impact of applying ML and UML in the system
analysis and design context [19].</p>
      <p>Once presented these works, we can observe that current XAI practice lacks adequate tools
and techniques to allow XAI experts to design their solutions and ensuring that the most
adequate techniques are selected while exploring potential alternatives. Moreover, this does
not depend on the specific context or dimensions where is applied, i.e., to define a conceptual
model is crucial to achieve the goal that each field faces.</p>
      <p>However, none of these works have addressed the modeling of XAI to correctly include it
in AI scenarios, which is essential to help XAI experts to select the most adequate explainable
techniques. Motivated by this unreached goal, we present a modeling approach to help the
XAI experts to select the most adequate explanations in the specific AI contexts, which will be
presented the next section.</p>
    </sec>
    <sec id="sec-5">
      <title>4. A modeling approach to define explanations</title>
      <p>In this section, we present our proposed conceptual model, which captures the key elements
included when XAI is applied in AI scenarios. The aim of this metamodel, which is aligned
with the UML [9] technique standardization, is allowing XAI experts to model and analyze the
diferent explanations to be generated, and AI models involved, in order to design and select the
most adequate XAI techniques and interfaces for each specific case study. In order to present
this conceptual model (Fig. 11), which helps the XAI experts to decide which of them are more
adequate, we have meticulously studied the SOTA of XAI (e.g., [8, 10]). In order to completely
present our proposed conceptual model, its diferent points of our proposal will be presented
below.</p>
      <p>First, our conceptual model captures the diferent kinds of explanations. This point takes
into consideration the diferent dimensions involved to correctly select the most appropriate
techniques depending on the specific case study.</p>
      <p>Second, this proposed model also captures how these explanations will be combined and
supported to present a complete explainable interface to the end user. Hence, the resulting
explanations generated will be more useful to end-users.</p>
      <p>Finally, it takes into consideration how to design the explainable interface, where the diferent
explanations will be included. Thus, end-users will be provided with a more complex a complete
interface to observe and interact, which is essential to help them to understand the reasons
behind the decisions made by the AI system. In this context, the diferent XAI techniques
selected will be included in the explainable interface [7].</p>
      <p>As a result of the introduction of the proposed XAI conceptual model, we obtain an XAI design
analysis process that helps the XAI expert to correctly select the most adequate explainable
techniques for the specific case studies.</p>
      <p>Therefore, our proposal lets the XAI experts analyze the case study where XAI will be
applied. Consequently, we present a conceptual model that includes the relevant elements in
XAI scenarios, which is presented in Figure 1. It shows how to design the explanations given
diferent elements.</p>
      <p>In the following, the proposed elements included in our conceptual model will be explained.
As we can observe in Fig. 1, where this conceptual model is presented, there are three diferent
type of elements included: classes (presented in a yellow color), abstract classes (presented
in a blue color), and enumerations (presented in a green color). Moreover, we have divided
the proposed elements in three diferent blocks to help to understand and apply our proposal.
Specifically, there are the explanation, technique and model blocks, which will be presented
below.</p>
      <p>First, the explanation block is presented. This block includes the “Explanation” abstract class
that captures the simple or multimodal (also called combined) explanation generated. Moreover,
this block also captures the “DomainKnowledge” class that supports the explanation through
diferent ways (included in the “DomainKnowledgeResourceEnum” enumeration: ontologies,
dictionaries and domain experts). The format of the explanations is also relevant in the
“TextFormat” and “VisualFormat” classes that indicate how the explanation will be presented. Moreover,
1Image in diferent formats located in repository
there is also included the “XAITask” class. In this class, we have defined diferent types of tasks
that can be represented. In this context, we propose to isolate the diferent previously-presented
post-hoc techniques (section 2) to provide this new concept of XAI tasks, which is closely linked
to the XAI techniques concept (the definition of these techniques is included in the proposed
conceptual model and will be presented in the next block). Specifically, this new concept
generates the explanations thanks to the application of the most appropriate XAI techniques. Hence,
the possible values for a type of task, which are presented in the “TypeTaskEnum” enumeration,
are [8]: text, visual, feature relevance, local, example, and simplification. Finally, this block
presents the “ExplainableInterface” class that contains the diferent explanations generated by
one XAI task. This class that takes into consideration the specific end-user (which can be an
ML expert, domain expert, or non-expert) and the visualization properties of the final format of
the explainable interface. Detailing the cardinalities, an explainable interface is build by at least
one explanation and can contain a lot of explanations; the domain knowledge can support zero
or many explanations (and, transitively, the explainable interface) and these explanations can
be supported by zero or many domain knowledge resources.</p>
      <p>Second, the technique block is focused on categorizing the diferent XAI techniques, where
an above-presented XAI task applies one or more of these XAI techniques. In this context, an
XAI technique always has a scope, which diferentiates between techniques focused on the
whole model or a subspace of this (global or local, respectively); a methodology, which refers
to how an explanation works (perturbation [20] or backpropagation [21, 22] based methods);
and an usage, which categorizes the techniques between the focused on specific AI models’
architectures or without depending on them (intrinsic or post-hoc, respectively). Due to space
constraints, we will not detail all techniques included in these categories, which are presented
in the proposed conceptual model (Fig. 1). Moreover, we should specify that the diferent
abovepresented categories can be combined depending on the specific XAI technique. For example,
the Local Interpretable Model-Agnostic Explanations (LIME) technique [23] is perturbation
based, post-hoc and could be local or global depending of the specific application.</p>
      <p>Third, the model block contains information about the AI model that should be explained.
In this context, the “AIModel” abstract class is provided with one or more type of the input
data and, after processing the data and executing diferent steps, provides one or more types of
the output data. Both input and output data are represented in the abstract class “Data” and
can be instanced as: structured data (.csv files, etc.), semi-structured data (.json files, etc.) and
unstructured data (images, etc.). Moreover, the AI model can be transparent or opaque [8]. On
the one hand, the transparent models are: Decision Trees (DT), Logistic Regression (LR), Linear
Regression (LR), K-Nearest Neighbors (KNN), Bayesian Models (BM), and General Additive
Models (GAM). On the other hand, there are diferent opaque models (Convolutional Neural
Networks (CNN), Transformers, etc.) that refer to AI architectures that can be categorized
as model-specific, which are analyzed by intrinsic techniques, and model-agnostic, which are
analyzed by post-hoc techniques.</p>
      <p>Finally, once modeled the previously-describe elements and enumerations, we achieve a
conceptual model that helps the XAI experts to apply XAI in AI scenarios. Hence, our
UMLstandardized proposal lets them to cover the diferent dimensions included in the XAI processes,
which is essential to select the most adequate XAI approaches in the specific case studies. In
the next section our case of application will be presented</p>
    </sec>
    <sec id="sec-6">
      <title>5. Case study</title>
      <p>In order to test the applicability of our proposal, we have applied it in a real case study.
Specifically, it has been applied to an existing project on AI-driven Attention-Deficit/Hyperactivity
Disorder (ADHD) diagnosis and treatment project, called Balladeer2. Therefore, in this section
we will present (i) the diferent steps and elements of our proposal specified to this scenario, and
(ii) the final explainable interface achieved thanks to having applied our proposal, as follows.</p>
      <sec id="sec-6-1">
        <title>5.1. Conceptual modeling to define the explainable interface in the ADHD context</title>
        <p>In the following, the diferent captured elements in the ADHD case study, which allow to define
the explainable interface and its explanations, will be presented in Fig. 23.</p>
        <p>First, the AI model presents an opaque nature that aims to diagnose the patients as positive
or negative ADHD cases. Specifically, it is a CNN model-agnostic architecture that processes
unstructured 2D Electroencephalography (EEG) signals -captured by using the emotiv headset
[24]- from the patients as input data, and provides the results in a structured data format (.csv
ifles). Moreover, this model consist of six parallel blocks of two one-dimensional (1D) kernels
that are applied on cascading, where each kernel presents a diferent length to extract features
at diferent frequencies and executes the elu activation function. Moreover, each kernel also
presents a number of 64 filters, a same padding mode and a number of 15 epochs. In order
to diagnose the ADHD for each patient, there is applied an average pool between these six
blocks and, after executing it, the sigmoid function is also applied to return a value of 0 (ADHD
negative case) or 1 (ADHD positive case). This above-described model architecture is shown in
Fig. 3.</p>
        <p>Second, the XAI expert aims to decode the black-box nature of the CNN model. In this context,
the XAI expert -the first author of this paper plays this role-, who has made use of the
previouspresented metamodel (Fig. 1), defines three diferent explanations that should be included in
the explainable interface. More specifically, these three explanations are defined such as local,
perturbation based and post-hoc [10], taking into consideration its scope, methodology and
usage, respectively. Moreover, two of them compose a multimodal explanation represented in
visual formats, and the other one is presented in a text format. These explanations are presented
below.</p>
        <p>The first explanation is a feature relevance XAI task. In order to achieve it, the SHAP
[25] technique has been selected as the most adequate, which is inside the sub-space of the
intersection of the local, perturbation and post-hoc XAI techniques spaces. Hence, we can
extract the most relevant brain sensors, i.e., which brain zones have presented a higher activity
during the tests applied and their events.</p>
        <p>The second explanation is a visual XAI task. In order to apply it, a customised technique is
implemented. Hence, there is presented a headplot where the more relevant sensors, provided
by the previous explanation Thus, there is applied a segmentation where the more relevant
sensors are emphasized in a red colour.</p>
        <sec id="sec-6-1-1">
          <title>2https://balladeer.lucentia.es/en/home-2/ 3Image in diferent formats located in repository</title>
          <p>Figure 2: Application of the proposed conceptual model in the ADHD case study.</p>
          <p>The third explanation is a text XAI task. This explanations translates the patients information
to an organized text distribution, which lets end-users to take this information into consideration
through generating key words, sentences a paragraphs.</p>
          <p>Finally, all above-presented points will be included in the explainable interface. This
explainable interface aims to help the neurologists, who are the specific end-users as domain
experts, to understand the logic behind the AI model decision-making process. Moreover, this
explainable interface will be organized in two parts: the left side for the headplot, where the
sensor relevance is included, and the right side for the patient information. Consequently, this
explainable interface will help the neurologists involved in the case study. In the following, this
explainable interface will be presented.</p>
        </sec>
      </sec>
      <sec id="sec-6-2">
        <title>5.2. Explainable interface</title>
        <p>Following the above-presented points, the explanations can be implemented. We then show the
ifnal explainable interface achieved, which aims to support the end-users: the neurologists.</p>
        <p>As presented in Fig. 4, the diferent headplots extracted from the diferent layers -before the
feature vectors are executed-, are included in the explainable interface. In this interface, it is
possible to navigate to observe the diferent headplots. Moreover, the patient’s information
captured apart from the AI system (weight, blood group, etc.) is also included.</p>
        <p>In this context, the sensors relevance presented in the headplots play a feature relevance role
-each sensor is each feature-, which is supported by a visual explanation -diferent colours in
the headplots-. Furthermore, there are diferent headplots to analyze depending on the specific
time point or event for the patient. On the other hand, there is patient’s information that can
help the neurologists to understand the diagnose and verify it: patient’s previous diagnoses,
blood group, etc.</p>
        <p>In Fig. 4, we can observe the explainable interface that supports the neurologists, which has
been achieved thanks to our proposal.</p>
      </sec>
    </sec>
    <sec id="sec-7">
      <title>6. Conclusions and future work</title>
      <p>Nowadays, AI systems have an enormous relevance in society, and this relevance is growing
day by day. Moreover, these systems are being applied in diferent fields. In this context, it is
necessary to analyse them properly before they reach society.</p>
      <p>To make the most of AI systems, it is crucial to provide explanations that can shed light on
the reasoning behind these systems decision-making processes, which generate the outputs.
This is especially important in advanced AI systems like DL models, which can produce precise
results but lack the ability to comprehend the rationale underlying their decisions.</p>
      <p>To address this issue, the field of XAI emerged, which ofers a range of techniques and options
to generate explanations that can supplement the limited transparency of existing AI systems.
However, despite the diversity of XAI techniques available, each tailored to explain specific AI
models and generate diferent types of information, there is still a lack of modeling approaches
to help the XAI experts to select the most adequate XAI explanations in the specific context,
which is essential to achieve comprehensive and efective explanations for end-users.</p>
      <p>Aiming to face this problem, in this paper we have bridged the XAI and conceptual modeling
ifelds. To achieve it, we have meticulously studied the most relevant works ( e.g., [8, 7, 10]) in
the XAI context to extract the key XAI elements that have been captured by our proposal.</p>
      <p>Thus, we have presented a conceptual model represented in an UML class diagram, which
captures these key elements in the XAI field, which will support the XAI experts to design and
implement explanations in AI scenarios. Specifically, our proposed conceptual model takes into
consideration (i) how the explanations should be generated; (ii) how these explanations will
be combined and supported to present a complete explainable interface to the end-users; and
(iii) what explainable interfaces will be generated so that end-users can see and interpret the
decision-making processes of the AI systems.</p>
      <p>In order to show the applicability of our proposal, we have applied it to an existing project on
AI-driven Attention-Deficit/Hyperactivity Disorder (ADHD) diagnosis and treatment, which is
a safe-critical area. Given the sensitivity of the information involved and the diverse set of the
end-users and recipients in the medical domain, our case study serves as an ideal example where
the modeling of XAI should be approached with care to ensure that each end-user receives the
appropriate information.</p>
      <p>As a result of the application of our proposal, we have been able to design an explainable
interface that provides diferent explanations adapted to the end-users: the neurologists. Thus,
it presents (i) the events EEG signals -captured by using the emotiv headset [24]- from the
patients, and (ii) the patient’s information that can help to understand the ADHD diagnosis
result. Consequently, our proposal not only helps the XAI expert to design and implement the
explainable interface, but also helps end-users to understand the logic behind the decisions
made by the specific AI system.</p>
      <p>In future works, our plans are: (i) to explore alternatives to apply the defined approaches
(e.g., situational method engineering [26]) (ii) to explore diferent abstraction levels such as
how to take into consideration certain aspects of the inputs for their adequate representation
in the explainable interface; due to the possible combinatorics possible between input data,
architectures and output data; (iii) to study how to formally define and use properly formed and
universal OCL [16] rules, based on the relevant SOTA of XAI, to ensure the correct design of
the model and avoid arbitrary linking the proposed elements; and (iv) to improve or make more
systematic the derivation of the diferent abstraction and technical levels to the final interfaces,
which will be presented to end-users. In this sense, we intend to carry out an experiment with
end-users to validate the diferent dimensions of the proposal aside from the purely functional
aspects. Consequently, (v) we will provide a multi-dimensional model-driven approach [27] that
facilitates faster and less costly XAI implementations in a semi-automatic way and also facilitates
the maintainability of XAI codes and their subsequent derivation [28, 29]. Finally, (vi) we will
provide the guidelines for the proposed models and (vii) apply a more thorough evaluation by
testing the final approach with diferent people, who will interact the XAI interface.</p>
    </sec>
    <sec id="sec-8">
      <title>Acknowledgments</title>
      <p>This work has been co-funded by (i) the AETHER-UA project (PID2020-112540 RB-C43) funded
by the Spanish Ministry of Science and Innovation, and (ii) the BALLADEER (PROMETEO/
2021/ 088) project funded by the Conselleria de Innovación, Universidades, Ciencia y Sociedad
Digital (Generalitat Valenciana).
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