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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>Towards an ontology-based system to foster Older Adults' Mental health via Indoor Comfort management</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Daniele Spoladore</string-name>
          <email>daniele.spoladore@cnr.it</email>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Anđela Ðinđić</string-name>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Walter Terkaj</string-name>
          <email>walter.terkaj@cnr.it</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>National Research Council of Italy (CNR-STIIMA)</institution>
          ,
          <addr-line>via A. Corti 12, 20133, Milan</addr-line>
          ,
          <country country="IT">Italy</country>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>National Research Council of Italy (CNR-STIIMA)</institution>
          ,
          <addr-line>via G. Previati 1E, 23900, Lecco</addr-line>
          ,
          <country country="IT">Italy</country>
        </aff>
      </contrib-group>
      <pub-date>
        <year>2026</year>
      </pub-date>
      <abstract>
        <p>The growing aging population raises critical challenges for mental health and independent living among older adults. Indoor comfort metrics - encompassing lighting, temperature, air quality, and ventilation - have been recognized as a key determinant of psychological well-being. Despite the evolution of Ambient Assisted Living (AAL) technologies, few systems directly address how indoor comfort afects mental health in older adults, a task requiring a multidisciplinary approach. This paper introduces OAIC (Older Adults Indoor Comfort), an ontology-based framework designed to bridge this gap by enabling intelligent, personalized indoor comfort management tailored to the mental health needs of the elderly. OAIC integrates standard ontologies such as SOSA, ICF, and ICD and models both general and tailored comfort settings based on expert knowledge and clinical metrics like the Geriatric Depression Scale. Through semantic rules, the system enables detection of deviations from comfort thresholds and triggers appropriate environmental adjustments via actuators. Two use cases illustrate the system's functionality in supporting individuals with depression and sleep disorders. The ontology was developed following the AgiSCOnt methodology, ensuring iterative collaboration with domain experts. Although in a prototypical phase, OAIC demonstrates strong potential to enhance mental health in aging populations by supporting non-pharmacological interventions through intelligent environmental adaptation. Future validation and stakeholder engagement are essential to assess its eficacy and broaden its adoption.</p>
      </abstract>
      <kwd-group>
        <kwd>eol&gt;Ontology-Based Systems</kwd>
        <kwd>Ambient Assisted Living</kwd>
        <kwd>Indoor Environmental Quality</kwd>
        <kwd>Older Adults' Mental Health</kwd>
        <kwd>Indoor Comfort Metrics</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <p>
        The progressive aging of the population is becoming a relevant issue for many countries worldwide.
In 2023, the World Health Organization (WHO) observed an increase in worldwide life expectancy
up to 73 years old [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ] – which happened in the past 75 years as a consequence of general wellbeing.
Life expectancy is longer in Western countries, although the aging problem afects all countries [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ]. In
Europe, most countries are facing an increase in the percentage of older adults (i.e., people aged 65 or
more) and, at the same time, a decrease in birth rates. This situation – also known as greying of Europe
phenomenon – is expected to exacerbate by 2050, when the number of older adults in Europe will touch
45% of the total EU-27 population [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ].
      </p>
      <p>
        Aging implies older adults often sufer from chronic conditions, including sensory loss, cognitive
decline, cardiovascular conditions, and impaired mobility, which can ultimately culminate in disability
[
        <xref ref-type="bibr" rid="ref4 ref5">4, 5</xref>
        ]. For older adults aged 85 or older, physical and cognitive impairments are expected to be systematic
[
        <xref ref-type="bibr" rid="ref6">6</xref>
        ]. Alongside physical impairments, mental health issues are common in adults over 65. Depression,
anxiety, loneliness, social isolation, and dementia are among the conditions that afect more than 20%
of this population, with symptoms often dificult to diagnose or mistaken as the results of aging [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ].
Furthermore, in some countries (e.g., some European countries, China, etc.), aging can result in an
increase in the national healthcare expenditure, which has to cover long-term care [8].
      </p>
      <p>In the past decade the WHO promoted Active Aging, a multidimensional and holistic approach that
includes physical, mental, and social well-being, as well as ongoing engagement in social, economic,
cultural, and civic activities. Active Aging is expected to make older adults healthier, socially-connected,
and make them live independently for longer periods of time [9, 10]. From a technological perspective,
Ambient Assisted Living (AAL) [11] emerged in the early 2000s as a technological paradigm to support
older adults’ independent living – particularly in Activities of Daily Living. AAL received a significant
push during the last ten years by the further development of other technological paradigms (i.e.,
Context Awareness, Internet of Things, Ambient Intelligence), which contributed to the development
of prototypical solutions in the areas of smart homes and assistive devices.</p>
      <p>Among the features of interest, AAL solutions also touch on indoor environmental quality (IEQ) and
its conditions. IEQ plays a significant role in human health, with key factors including thermal comfort,
indoor air quality and ventilation, visual and acoustic comfort, hygiene, and safety. In particular,
researchers have focused their attention on the efects air pollutants and air quality have on health [ 12],
which can also include mental issues. The efects of indoor temperature and lighting have also been
intensively investigated [13, 14]. The problems generated from indoor environmental conditions are
also a concern for older adults, particularly for those characterized by chronic conditions. In particular,
air quality and pollution have been found to significantly exacerbate respiratory conditions and to
impact mental health as well, contributing to increased depressive and anxious symptoms [15, 16].
Several studies underline the correlations between noise levels, indoor temperature, lighting levels,
and the emotional well-being of older adults. These environmental factors can play a pivotal role
in exacerbating mental illnesses, decreasing sleep eficiency, and accelerating cognitive decline (as
summarized in Peralta et al. [17]). Indoor comfort-related issues are also a major concern for older
adults in residential settings and nursing homes [18].</p>
      <p>These considerations highlight the primary role AAL solutions can cover in supporting older adults
living autonomously and in a healthy way by leveraging advanced technologies for indoor environmental
monitoring and control. Specifically, the continuous assessment of key comfort parameters enables AAL
systems to maintain optimal living conditions tailored to the needs of elderly individuals. By ensuring
a stable and healthy indoor environment, these systems help mitigate the impact of environmental
factors on mental health, thus contributing to the prevention of cognitive decline and mental health
deterioration.</p>
      <p>However, AAL solutions are mostly focused on physical impairments and mild cognitive disabilities
(ranging from mild memory issues to early stages of dementia), with interventions devoted to identifying
potential health risks, medication management, daily activities reminders, and behavioral support
[19, 20, 21]. Indoor comfort metrics and their management in AAL solutions are often treated as a
secondary aspect or assumed to be inherently adequate, with primary focus placed on safety, mobility,
and medical monitoring. As a consequence, there is a notable lack of Ambient Assisted Living (AAL)
solutions specifically designed to manage indoor comfort as a means of mitigating mental health risks
among older adults. Moreover, addressing this gap requires a multidisciplinary approach that involves
both clinical and non-clinical personnel in the monitoring and adaptation of indoor environments to
support older adults’ mental health.</p>
      <p>This work presents a prototypical ontology-based system to address the identified research gap.
Specifically, this paper introduces an ontological framework (Older Adults Indoor Comfort - OAIC) and
its engineering process, focusing on the modelling choices aimed at supporting the mental well-being
of older adults. The remainder of this paper is organized as follows: Section 2 highlights some of the
most relevant works in this field, while Section 3 provides the theoretical background on older adults’
mental health issues and presents the results of a literature survey on the topic of indoor environmental
conditions and their efects on the elderly. Section 4 delves into the OAIC ontology engineering process,
illustrating the resources involved in the process and the resulting model. Section 5 presents two use
cases to describe the expected functioning of indoor comfort management performed with the ontology.
Section 6 discusses some limitations of the proposed approach and outlines the future research directions,
including proposals for validating OAIC and its inferences. Finally, the Conclusions summarize the
main outcomes of this paper.</p>
    </sec>
    <sec id="sec-2">
      <title>2. Related work</title>
      <p>The use of ontologies for modelling indoor comfort metrics and to act as the backbone of AAL solutions
is no novelty. In the past fifteen years, many articles have tackled the issue of modelling occupants,
their needs, impairments, devices and actuators, and human activity within AAL frameworks. Indoor
comfort metrics, however, were not often the main focus of ontology engineering, nor were older adults’
mental health needs. In most of the ontology-based AAL solutions, the main comfort metrics impacting
human health – i.e., indoor air quality, temperature, humidity, lighting, and noise – were implicitly
modelled as a collection of data (coming from sensors) [22]. Sometimes, occupants’ preferences in a
smart environment include comfort metrics: in the AATUM ontology, a Preference class includes the
possibility to specify a user’s preferred temperature value for a room or a lighting setting when the
user performs specific activities (such as watching TV with lights of)[ 23]. In other ontologies, such as
OntoDomus [24], comfort is nuanced as one of the contextual elements of a smart environment, and its
management seems to be relegated to a matter of measurements performed by sensors.</p>
      <p>
        After 2020, when research on the role played by indoor comfort on human health was being explored
more extensively, even AAL solutions started to pay more attention to comfort modelling and to carve
out a more relevant role for it. In [25] and [26], temperature, lighting, and air quality measurements
performed by sensors are used to trigger some actuations – aimed at avoiding the exacerbation of
occupant’s physical conditions, such as respiratory, visual, or cardiovascular ones. In these works,
occupants’ impairments are modelled leveraging international health standards, i.e., WHO’s
International Classification of Functioning, Disability and Health (ICF)[
        <xref ref-type="bibr" rid="ref8">27</xref>
        ] or International Classification of
Diseases (ICD)[
        <xref ref-type="bibr" rid="ref9">28</xref>
        ], and a set of rules assigns to each condition a suitable comfort metric setting. Unlike
these works, ComfOnt[
        <xref ref-type="bibr" rid="ref10">29</xref>
        ] – a domain ontology developed to support occupants with special needs in
managing domestic appliances’ energy consumption while maintaining their preferred levels of indoor
comfort – builds on the concept of occupant’s comfort settings: the current environmental conditions –
assessed via a network of sensors – are compared against the preferred temperature, lighting and air
quality values modelled within the ontology. A set of rules triggers appropriate actions when any of
the parameters deviate from the specified comfort range.
      </p>
      <p>
        The integration of comfort metrics and energy saving in ontology-based smart solutions is also
represented in more recent eforts. For example, IAQ focuses on modelling indoor air quality
(specifically, temperature, humidity, PM2.5, and PM10) to improve occupants’ health, comfort, and energy
consumption. Also in this case, ICF-based health profiles describing physical conditions (including
chronic ones) are linked to comfort settings via rules. Sustainable and eficient energy consumption
with indoor comfort is also the aim of the AAL solution described in [
        <xref ref-type="bibr" rid="ref11">30</xref>
        ], an ontology-based digital
twin that models, among other concepts, occupants’ preferences in terms of indoor comfort (with
specific reference to indoor temperature and humidity). Also in [
        <xref ref-type="bibr" rid="ref12">31</xref>
        ], the ontology provides a digital
twin for the integration of heterogeneous data (sensor data, occupants’ characteristics, weather, etc.)
and to inform actuators (e.g., HVAC, lighting, etc.) so that they can respond dynamically to occupants’
preferences. However, it is worth observing that while all the solutions are devoted to supporting older
adults and meeting their specific needs, the cognitive and mental health aspects of the elderly are often
neglected. In some works, it is hinted that the proposed solutions may support occupants’ cognitive
aspects, but no actual modelling of the relationships occurring between indoor comfort metrics and
mental health issues is presented. On the contrary, the solution presented in Section 4 aims at making
these relationships explicit and exploiting them for actuating indoor comfort modifications capable of
fostering occupants’ mental health.
      </p>
    </sec>
    <sec id="sec-3">
      <title>3. Indoor Environmental Conditions and Mental Health in Older</title>
    </sec>
    <sec id="sec-4">
      <title>Adults</title>
      <p>
        Mental health challenges in older adults, including depression, anxiety, sleep disturbances, and cognitive
decline, are increasingly recognized as critical public health issues [
        <xref ref-type="bibr" rid="ref13">32</xref>
        ]. According to WHO’s data, 14%
of older adults live with a mental disorder, and around 27% of suicides are among people aged 60 or more.
Age-related biological changes such as altered circadian regulation, reduced thermoregulation, sensory
decline, and increased sedentary behavior render this population especially sensitive to environmental
factors. These vulnerabilities are compounded by social isolation and reduced mobility, leading to
increased time spent indoors. Consequently, IEQ - encompassing lighting, temperature, and ventilation
- emerges as a crucial determinant of mental health in older adults. In the following, the main indoor
comfort metrics impacting older adults’ mental health are discussed. Recent evidences from literature
reviews were gathered and summarized to provide an overall picture of the role played by IEQ in
exacerbating or reducing mental-related conditions, focusing on those metrics that constitute the main
focus of the proposed OAIC ontology-based system.
      </p>
      <p>
        Sleep and circadian rhythm: In the elderly population, circadian rhythm disruption is a core
mechanism linking environmental stimuli to psychological outcomes. Light and temperature are key
“zeitgebers” (time cues) that help synchronize circadian rhythms [
        <xref ref-type="bibr" rid="ref14">33</xref>
        ]. Poor lighting, thermal discomfort,
and insuficient ventilation may contribute to physiological stress, hormonal imbalance (e.g., melatonin
suppression, cortisol elevation), and neuroinflammation: factors associated with mood disorders and
sleep problems.
      </p>
      <p>
        Lighting exposure: Light exposure plays a pivotal role in regulating circadian rhythms, mood, and
cognitive function in older adults. Circadian lighting systems that simulate natural daylight cycles, with
gradual shifts in intensity and colour temperature, have demonstrated benefits in reducing depressive
symptoms and agitation while enhancing sleep quality [
        <xref ref-type="bibr" rid="ref15">34</xref>
        ]. High-intensity daytime light exposure has
been associated with improvements in cognition and decreases in depressive symptomatology over
both short and long-term periods [
        <xref ref-type="bibr" rid="ref16">35</xref>
        ]. These improvements are linked to better circadian rhythm
stabilization and sleep eficiency, both commonly disrupted in depressive disorders. Satisfaction with
indoor lighting correlates positively with emotional well-being, whereas inadequate lighting is associated
with increased loneliness, negative afect, and sleep disturbances [
        <xref ref-type="bibr" rid="ref17">36</xref>
        ]. Although some studies report
mixed results, the preponderance of evidence supports appropriate lighting interventions as an efective
non-pharmacological approach to enhancing mental health, particularly for those with limited mobility
or cognitive impairment. A review of current literature reveals consistent associations between IEQ
parameters and mental health outcomes in the elderly: daylight and circadian-aligned artificial lighting
are shown to mitigate depression and improve sleep quality. Controlled trials demonstrate that daytime
exposure to bright light (2,500 lux) significantly reduces depressive symptoms and increases sleep
eficiency in older adults, including those with dementia [
        <xref ref-type="bibr" rid="ref18 ref19">37, 38</xref>
        ]. Conversely, nighttime exposure to
indoor lighting above 5 lux has been linked to a higher risk of depression, likely through circadian
disruption and melatonin suppression [
        <xref ref-type="bibr" rid="ref20">39</xref>
        ].
      </p>
      <p>
        Temperature: Depression, cognitive impairment, and dementia are significantly influenced by
environmental conditions, particularly temperature regulation. Elevated ambient temperatures and
greater temperature variability have been strongly associated with negative psychological and cognitive
outcomes in older adults. Meta-analytic evidence [
        <xref ref-type="bibr" rid="ref21">40</xref>
        ] highlights that inadequate indoor temperature
control can exacerbate these mental health conditions, underlining the importance of maintaining a
stable and comfortable indoor climate for emotional well-being in aging populations. Periods of extreme
heat often coincide with spikes in hospital admissions and mortality among older adults, especially those
with pre-existing mental health conditions or who are socially isolated. While older adults generally
prefer warmer indoor temperatures than younger individuals, surpassing comfort thresholds can lead
to reduced life satisfaction and heightened psychological distress [17]. Conversely, prolonged exposure
to low indoor temperatures is frequently associated with depressive symptoms, disrupted sleep, and
diminished quality of life [
        <xref ref-type="bibr" rid="ref22">41</xref>
        ]. Cold environments provoke physiological stress responses, potentially
triggering or worsening depression, particularly in those with impaired mobility or thermoregulatory
capacity. Additionally, short-term temperature fluctuations, such as diurnal temperature range, have
been linked to increased hospital admissions and mortality from mental illness [
        <xref ref-type="bibr" rid="ref23">42</xref>
        ]. Depression is
especially sensitive to such variability, with symptoms like anxiety and hopelessness often emerging
during sudden temperature changes. Challenges remain in precisely attributing efects due to the reliance
on outdoor temperature data without detailed indoor exposure assessments. Furthermore, individuals
with dementia exhibit altered thermal perception and responses, necessitating personalized thermal
management strategies to reduce agitation and improve sleep quality [
        <xref ref-type="bibr" rid="ref24">43</xref>
        ]. Thermal comfort plays a vital
role in both cognitive performance and emotional regulation. Studies identify a thermoneutral zone
between 20–24°C (68–75°F) as optimal for older adults. Exposure to temperatures outside this range
is associated with impaired cognitive performance, poor sleep quality, and increased psychological
stress [
        <xref ref-type="bibr" rid="ref25 ref26">44, 45</xref>
        ]. Nighttime heat in poorly ventilated or uncooled environments, common in institutional
settings, exacerbates sleep fragmentation.
      </p>
      <p>
        Air quality: Air quality is another essential determinant of mental health and cognitive function.
Exposure to fine particulate matter (PM2.5), PM10, nitrogen dioxide (NO), and ozone (O) has been
consistently linked to increased risks of depression, anxiety, cognitive decline, and neurodegenerative
diseases such as dementia [
        <xref ref-type="bibr" rid="ref27">46, 47, 48</xref>
        ]. For example, a 5 g/m³ rise in PM2.5 has been associated with a
0.62% increase in depressive symptoms [
        <xref ref-type="bibr" rid="ref27">46</xref>
        ]. These efects are mediated through systemic inflammation,
neuroinflammation, and disruptions in sleep and circadian regulation—key processes implicated in
depression. Within residential and care settings, indoor pollutants such as volatile organic compounds
(VOCs), carbon dioxide (CO), environmental tobacco smoke, mould, and emissions from fuel combustion
have been linked to inflammation, impaired brain connectivity, and elevated anxiety and depression
[18]. Frequent exposure exacerbates symptoms of low mood, fatigue, and cognitive slowing. Biological
pathways, including oxidative stress, neuroinflammation, and dysregulated cortisol secretion, underpin
these associations [48]. Moreover, sleep disturbances and brain structural changes serve as intermediate
mechanisms linking pollution exposure to depressive symptoms, particularly in at-risk older adults
[47]. Comparative studies highlight the protective efect of cleaner air, with lower depression rates
and improved emotional well-being observed in less polluted environments [47]. Intervention studies
demonstrate that improving indoor air quality through enhanced ventilation, filtration, and cleaner fuel
use reduces depressive symptoms and supports overall mental health [18].
      </p>
    </sec>
    <sec id="sec-5">
      <title>4. OAIC Ontology Engineering Process</title>
      <p>The development of OAIC took advantage of an existing agile methodology (AgiSCOnt [49]), which
relies on a collaborative approach involving domain experts and ontologists in acquiring a conceptual
map of the domain(s) of interest. The knowledge elicitation and acquisition phases benefited from the
involvement of domain experts, including clinical personnel (2 gerontologists working in a hospital,
2 psychologists, 2 biomedical engineers), architects and designers (3) involved in the reconfiguration
of living environments for older adults, and computer scientists (2). These activities were conducted
within the framework of the Italian PNRR Research Project Age-It 1. Following AgiSCOnt’s steps (i.e,
Analysis and conceptualization, Development and test, and Ontology use and updating), domain experts
were involved iteratively in the definition and refinement of a conceptual map. The prototypical OAIC
ontology is available online 2.</p>
      <sec id="sec-5-1">
        <title>4.1. Analysis and conceptualization</title>
        <p>During this step, the findings from diferent scientific and gray literature sources (see Section 3) were
gathered and discussed with domain experts. The discussion brought to the definition of a conceptual
map (sketched in Figure 1 and which does not rely on any formalism to allow experts’ maximum
freedom), and the definition of some indoor comfort metrics’ specifics, as detailed in the following
subsection. In particular, the domain experts deemed it essential to point out that there exists a neutral
comfort setting, which is suitable for all older adults with mental conditions, although some more
severe conditions may require a tailored set of comfort specifications. Also, experts highlighted that
the selection of comfort settings (particularly, tailored ones) may be the result of a discussion with the
older adult’s physician and that the older adult alone may not be self-suficient in setting the comfort of
1Project website: https://ageit.eu/wp/s-p-o-k-e-9/
2Ontology available at: https://w3id.org/ontocare/oaic
his/her house, thus requiring the assistance of a caregiver. All domain experts agreed that the scope of
the OAIC ontology is to prevent the exacerbation of older adults’ mental conditions by modifying the
indoor comfort when occupants are sojourning in a room: experts expected the ontology to identify the
harmful comfort metrics and to trigger a proper response.</p>
      </sec>
      <sec id="sec-5-2">
        <title>4.2. Development and test</title>
        <p>The conceptual map was then converted into an ontology, leveraging OWL 2 DL representation language
[50] with the addition of rules written with Semantic Web Rule Language (SWRL) [51]. Considering the
domains represented in the conceptual map and the existing ontological models, OAIC was developed
based on the following modelling choices:
• The health standards pertaining to psychological and a person’s functioning were defined by
domain experts; this resulted in the reuse of (subsets of) the ICD and the ICF for the disease and
functioning component, and brought to modelling some clinical standards adopted by
psychologists to quantify common mental conditions, such as anxiety, depression, and sleep disorders. In
particular, the need for quantifying some psychological and physical factors emerged as pivotal
to understanding the type of adaptations the comfort should undergo.
• The portion of the map depicting sensors, actuators, and their measurements and actuations
(performed on some comfort metrics, which are physical magnitudes) relies on the reuse of the
Sensor-Observation-Samples-Actuators (SOSA) ontology [52].
• The definition of neutral and tailored comfort settings should be made explicit, so that (if necessary)
settings could be changed over time, following occupants’ health condition modification.</p>
        <p>The reuse of SOSA, ICD, and ICF was performed as "soft reuse" (as defined in [ 53]), importing those
entities that were deemed as relevant for the domains at hand. Also, considering OAIC’s specific focus
on mental health, only a few ICD classes were modelled, while ICF classes included in OAIC serve the
purpose of illustrating the ontology’s scalability (i.e., the ontology can possibly encompass also physical
and mental conditions). The following subsections delve into OAIC’s structure.</p>
        <sec id="sec-5-2-1">
          <title>4.2.1. Health condition</title>
          <p>A oaic:HealthCondition is linked to its oaic:Occupant via the oiac:hasHealthCondition
object property and is described by relying on an existing ontology design pattern [54] (Figure 2).</p>
          <p>This pattern allows linking oaic:HCDescriptor individuals to a health condition; each descriptor
is characterized by either the ICD code describing the occupant’s mental disorder or the ICF codes
representing the impaired functions (with the datatype property oaic:ICFGenericQualifier for
quantifying the magnitude of the impairment). To assess and quantify the most common mental
disorders afecting older adults, OAIC models as datatype properties the results of widely adopted tests:
• Depression is quantified using the Geriatric Depression Scale (GDS) – Short Version [ 55]; this
scale may be used to monitor depression over time in all clinical settings. Any score above 5 on
the GDS can be considered as a mild depression, while scores between 5 and 8 can be considered
moderate depressive disorder, and finally, scores greater than 8 indicate severe depressive disorder.
• Anxiety is quantified relying on the Geriatric Anxiety Inventory (GAI) - Short Form, which, for
scores greater than or equal to 3, indicates a possible form of anxiety.
• Sleep disorder is quantified with the Geriatric Sleep Questionnaire (GSQ) - 6 item version [ 56],
which gives positive results for scores above 15.</p>
        </sec>
        <sec id="sec-5-2-2">
          <title>4.2.2. Sensors, measurements, and actuators</title>
          <p>OAIC reuses many concepts from SOSA, namely sosa:Sensor, sosa:Observation, which becomes
oaic:Measurement, and sosa:Actuator, together with all the object and datatype properties
relevant for the correct functioning of the related patterns. Each sensor performs observations, which
are characterized by an ID, a datetime stamp, and a sosa:hasSimpleResult property that
explicits the measurement value. Each sosa:Observation is expressed in a unit of measure (by reusing
the Ontology of units of Measure (OM) [57]) and assesses the value of a sosa:Property, physical
characteristics of interest which, in OAIC case, are the set of comfort metrics measures by sensors
(i.e., CO, CO, CO, TVOC, PM2.5, flicker, humidity, illuminance, ventilation, temperature). Similarly,
sosa:Actuators perform sosa:Actuation over (one or more) sosa:Property. Both sensors and
actuators are located in dogont:Rooms, the set of rooms composing a domestic environment - borrowed
from a subset of the DogOnt model [58]. Figure 3 depicts the TBox and the relationships occuring
among these concepts.</p>
        </sec>
        <sec id="sec-5-2-3">
          <title>4.2.3. Comfort setting</title>
          <p>
            Comfort settings are instantiated as individuals of the oaic:ComfortSetting class, which is further
specialized into the oaic:GeneralComfortSetting and oaic:TailoredComfortSetting
subclasses. This partition answers to experts’ request of distinguishing between a neutral comfort setting
and tailored settings that are explicitly developed to support the healing of specific mental conditions.
The choice of modelling comfort settings as individuals traces back to previous studies [
            <xref ref-type="bibr" rid="ref10">29, 26</xref>
            ], in which
the definition of user-centered settings was defined. Therefore, as depicted in Figure 4, each comfort
setting owl:Individual is characterized by a number of descriptors equal to the sosa:Property
that needs to be observed; then, each descriptor is completed by a datatype property specifying the value
of the involved property. The oaic:GeneralComfortSetting individual foresees the definition of
seven settings - thus, it involves seven descriptors.
          </p>
          <p>As an example, the following OWL code (serialized in Turtle) represents the definition of maximum
and minimum indoor temperatures (for winter and summer seasons) assigned to the oaic:CSDescr2-1
descriptor for a oaic:GeneralComfortSetting individual:
o a i c : CSDescr2 −1 r d f : t y p e owl : N a m e d I n d i v i d u a l , o a i c :</p>
          <p>C o m f o r t S e t t i n g D e s c r i p t o r ;
o a i c : s e t s O b s e r v a b l e P r o p e r t y o a i c : T e m p e r a t u r e ;
o a i c : TempSummerMax " 2 3 " ^ ^ x s d : i n t ;
o a i c : TempWinterMax " 2 2 " ^ ^ x s d : i n t .</p>
          <p>According to the domain experts, the general comfort setting specifies the following comfort values
for seven observable property:
• CO maximum concentration: 800 ppm;
• standard lighting set at 400 lux;
• PM2.5 maximum concentration: 10 µg/m3;
• winter indoor temperature between 20 and 22° C., summer indoor temperature between 23 and
26° C.;
• winter indoor humidity between 20 and 50%, summer indoor humidity between 40 and 60%;
• CO maximum concentration: 300 ppm;
• TVOC (Total Volatile Organic Compounds) maximum concentration: 100 ppb.
4.2.4. Rules
To illustrate the business logic underlying OAIC [59], rules were developed with domain experts.
Considering the expressiveness required by the use cases, SWRL was chosen as rule language. The
rules serve three purposes:
• Classifying an oaic:Occupant’s oaic:HealthCondition according to the magnitude of
his/her scale value(s): for instance, the rule
O c c u p a n t ( ? o c c ) , h a s H e a l t h C o n d i t i o n ( ? occ , ? hc ) , h a s D e s c r i p t o r ( ? hc
, ? hcd ) , G D S s c a l e ( ? hcd , ? g d s ) , g r e a t e r T h a n O r E q u a l ( ? gds , 9 ) ,
l e s s T h a n O r E q u a l ( ? gds , 1 1 ) −&gt; 6 A71 . 1 ( ? hc )
checks for the occupant’s Geriatric Depression Scale (attributed by a clinician) and classifies the
health condition as belonging to the ICD icd:6A71.1 (labelled "Recurrent depressive disorder,
current episode moderate - without psychotic symptoms").
• Checking whether a sosa:Observation individual value falls within the ranges specified by the
oaic:GeneralComfortSetting (or the oaic:TailoredComfortSetting if it is specified).
• In case a values exceeds the threshold(s) represented in the oaic:GeneralComfortSetting
or oaic:TailoredComfortSetting, identify the proper sosa:Actuator and activate it (by
setting true the value of the oaic:activate datatype property).</p>
          <p>Rules were defined with domain experts during the Analysis and conceptualization phase and represent
a subset of those cases experts have experienced during their working activities. Considering the
prototypical nature of OAIC, the focus of rules was shifted towards older adults and their mental issues,
and indoor comfort metrics management, rather than representing actuation in a complete way. In the
following Section 4.3, three use cases depicting the role played by SWRL rules are presented.</p>
        </sec>
      </sec>
      <sec id="sec-5-3">
        <title>4.3. Use cases</title>
        <p>To conclude the Development and test phase foreseen in AgiSCOnt, the prototype ontology was tested
against some use cases. Their purpose is to show domain experts and ontologists whether the prototype
complies with their expectations and to rectify authoring issues - if acknowledged. The reasoner Pellet
[60] was selected due to its ability to treat SWRL built-ins.</p>
        <sec id="sec-5-3-1">
          <title>4.3.1. Occupant with mild depression</title>
          <p>Mr. Arco (82) lives alone in his apartment and sufers from mild depression ( icd:6A71.0), reporting
a GDS score equal to 7. Moreover, he is afected by Chronic Obstructive Pulmonary Disease (COPD)
(icd:CA22), which limits his freedom of movement and activities. To avoid COPD exacerbation and to
mitigate his depression, the air purifier (a sosa:Actuator) is activated whenever the following rule is
true:
O c c u p a n t ( ? o c c ) , h a s H e a l t h C o n d i t i o n ( ? occ , ? hc ) , ( 6 A71 . 0 o r 6 A71 . 1 o r
6 A71 . 3 o r 6 B00 o r 6 B01 o r 6 B04 ) ( ? hc ) , l o c a t e d I n ( ? occ , ? room ) ,
O b s e r v a t i o n ( ? o b s ) , madeBySensor ( ? obs , ? s ) , l o c a t e d I n ( ? s , ? room ) ,
o b s e r v e d P r o p e r t y ( ? obs , ? p r o ) , h a s S i m p l e R e s u l t ( ? obs , ? v ) ,
d e f i n e d C o m f o r t S e t t i n g s ( ? occ , ? c s ) , h a s C o m f o r t S e t t i n g D e s c r i p t o r ( ?
c s , ? c s d ) , CO2max ( ? csd , ? vmax ) , g r e a t e r T h a n O r E q u a l ( ? v , ? vmax ) ,
C O 2 A c t u a t o r ( ? a ) , l o c a t e d I n ( ? a , ? room ) , a c t u a t e O n ( ? a , ? p r o ) −&gt;
a c t i v a t e ( ? a , t r u e )</p>
          <p>This simple rule allows Mr. Arco to avoid his respiratory conditions and the exacerbation of his
mental disorder. This rule works together with similar rules setting the minimum lighting foreseen by
the oaic:GeneralComfortSetting, as well as other rules monitoring air quality.</p>
        </sec>
        <sec id="sec-5-3-2">
          <title>4.3.2. Occupant with sleep disorders</title>
          <p>Mrs. Rossi (76) lives on her own after her husband’s departure. She sufers from chronic insomnia
(icd:7A00) and other diagnosed sleep function disorders (icd:VV01). Her physicians recommended
an indoor temperature around 20° C. during sleep time and the adoption of blackout shutters to limit
exposure to light during the night. Her daughter sets up a TailoredComfortSetting to implement
these changes in Mrs. Rossi’s bedroom. Therefore, the following rules are enforced:
The two rules exploit the equivalence sosa:Observation oaic:Measurement, which
enables the generation of two subclasses of measurement (oaic:NightObservation and
oaci:DayObservation) which depend on the specific sosa:resultTime value attached to each
observation. In this way, the caregiver can set the night (and day) duration, and the actuators will
activate only if the indoor measurements are performed at a specific time of the day.</p>
        </sec>
      </sec>
    </sec>
    <sec id="sec-6">
      <title>5. Limitations and Future research directions</title>
      <p>The work on OAIC is still in its early stages, and several limitations remain to be addressed. First,
considering the prototypical characteristic of the ontology, the focus on older adults’ mental health is
mostly on single disorders; however, as highlighted in Section 3, older adults may face more than one
mental disorder at the same time. In the next stages, domain experts will be involved in how to tackle
multiple mental conditions and comorbidities, identifying priorities to avoid conflictual comfort settings.
Among the mental issues not explicitly addressed in this work, solitude also needs further investigation;
to this end, two research directions can be followed: 1) recurring to domain experts’ knowledge and
model solitude as if it was a mental health concern, and b) including OAIC in a broader AAL framework
which can foster digital socialization (e.g., as in [61]). From an ontology perspective, the representation
of the actuation is currently simplistic. This is partly due to the necessity of focusing on older adults’
mental health, and partly to the need to identify a) a set of actuators that can be controlled remotely
and b) other relevant ontologies that can be used in this field. So far, the OAIC ontology has completed
the first two phases of AgiSCOnt’s methodology (i.e., Analysis and conceptualization and Development
and testing): with the interaction with other domain experts and the collection of further requirements,
the ontology can change considerably in some aspects. It is also relevant to underline that, so far, OAIC
deals with single occupants (older adults living alone or living in a nursing home in which they have
their own room). This limitation must be assessed to identify the possibility of having OACI manage
diferent conditions for multiple occupants (characterized by diferent health conditions). Nevertheless,
it is also fundamental to gather consensus on the model and its scope. To this end, OAIC needs to be
disseminated to other relevant stakeholders and an evaluation of its inferences and their values for the
stakeholder community must be performed (as it happened for other health-related and ontology-based
projects [62, 63]). This is part of a comprehensive, evidence-based validation strategy informed by
practices in architecture, gerontology, and psychology [64]. Semi-structured interviews conducted with
stakeholders have the opportunity to explore the emotional and content relevance of system constructs
and collect qualitative suggestions for enhancement.</p>
    </sec>
    <sec id="sec-7">
      <title>6. Conclusions</title>
      <p>This work presents OAIC, an ontology-based system aimed at supporting the mental health of older
adults by managing indoor comfort conditions. Unlike traditional AAL solutions, OAIC uniquely
emphasizes the correlation between environmental metrics and mental well-being, ofering tailored
comfort interventions through semantic modelling and automated actuation. Developed collaboratively
with clinical and technical experts, OAIC integrates standardized health classifications and sensor data
to infer actionable insights, thereby enabling personalized, health-supportive environments. Initial use
cases demonstrate the feasibility of addressing specific mental health conditions, such as depression
and sleep disorders, through indoor environment control. While still in development, OAIC provides a
foundation for future systems that promote psychological well-being and independent living among
the elderly. Future work will focus on validation, refinement, and stakeholder evaluation to ensure the
clinical relevance, usability, and integration of the ontological model into broader AAL ecosystems.</p>
    </sec>
    <sec id="sec-8">
      <title>Acknowledgments</title>
      <p>This paper was developed within the project funded by NextGenerationEU-“Age-It-Ageing well in an
ageing society” project (PE0000015), National Recovery and Resilience Plan (NRRP) -PE8-Mission4, C2,
Intervention 1.3”.</p>
    </sec>
    <sec id="sec-9">
      <title>Declaration on Generative AI</title>
      <p>The author(s) have not employed any Generative AI tools.
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