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  <front>
    <journal-meta>
      <journal-title-group>
        <journal-title>A. M. Tirado);</journal-title>
      </journal-title-group>
      <issn pub-type="ppub">1613-0073</issn>
    </journal-meta>
    <article-meta>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Alba Morales Tirado</string-name>
          <email>alba.morales-tirado@open.ac.uk</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>
          <xref ref-type="aff" rid="aff3">3</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Enrico Daga</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>
          <xref ref-type="aff" rid="aff3">3</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Enrico Motta</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>
          <xref ref-type="aff" rid="aff3">3</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>HECON Ontology.</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>
        <aff id="aff0">
          <label>0</label>
          <institution>FHIR - Fast Healthcare Interoperability Resources</institution>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>Health events</institution>
          ,
          <addr-line>Ontology, Knowledge Graph, Emergency Support, SNOMED CT</addr-line>
          ,
          <country country="US">USA</country>
        </aff>
        <aff id="aff2">
          <label>2</label>
          <institution>Hersonissos</institution>
          ,
          <country country="GR">Greece</country>
        </aff>
        <aff id="aff3">
          <label>3</label>
          <institution>KMi, The Open University</institution>
          ,
          <addr-line>Milton Keynes</addr-line>
          ,
          <country country="UK">United Kingdom</country>
        </aff>
      </contrib-group>
      <pub-date>
        <year>1952</year>
      </pub-date>
      <volume>000</volume>
      <fpage>0</fpage>
      <lpage>0002</lpage>
      <abstract>
        <p>Health records contain extensive information, including conditions, test results, procedures, and appointments. These data reveal past medical observations that could allow drawing a picture of the current health state of a patient. Widely adopted clinical terminology taxonomies, such as SNOMED CT and the FHIR standard, facilitate the processing and exchange of electronic health records. However, despite these eforts, the task of estimating whether a particular condition is afecting a patient's health at a certain point in time is not supported yet.</p>
      </abstract>
      <kwd-group>
        <kwd>ample</kwd>
        <kwd>appointments</kwd>
        <kwd>laboratory tests</kwd>
        <kwd>surgeries</kwd>
        <kwd>allergies)</kwd>
        <kwd>which can help draw a picture of</kwd>
      </kwd-group>
    </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>
        CEUR
Workshop
Proceedings
the person’s state of health at a given point in time. For instance, the analysis of standardised
medical data (such as, EHRs using SNOMED CT terminology) could reveal chronic or
ongoing issues, recent procedures or other health-related events that can impact on the current
health condition3 of a patient. Delivering this information to first responders represents an
essential asset when making decisions and planning evacuation operations [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ]. However, the
lack of knowledge about clinical conditions’ evolution over time represents a challenge when
implementing intelligent systems that can automatically estimate a person’s current state of
health.
      </p>
      <p>
        This paper addresses these challenges by adopting a knowledge engineering approach. We
present HECON4, the Health Condition Evolution Ontology, as a formal model representing
the evolution of health events over time. In particular, the process of recovering from a health
situation is not limited to a fixed convalescence time. For example, conditions typically have
a temporal span associated with their evolution, e.g., improving or worsening over a certain
period or, alternatively, becoming chronic. Our ontology aims to support the identification of
ongoing health events at a given point in time by representing conditions’ evolution information.
We link the health evolution data to the SNOMED CT taxonomy and extend it by aggregating
information of the recovery time of conditions. We motivate the design rationale of the ontology
by considering a fire emergency scenario as our reference application, which provides both
a source for requirements and a validation setting. HECON is the result of previous research
[
        <xref ref-type="bibr" rid="ref10 ref8 ref9">9, 8, 10</xref>
        ] to represent and reason on healthcare data and provide usable information to emergency
services in the context of fire event.
      </p>
      <p>
        This paper expands the model proposed in [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ] by formally encoding its concepts using Web
Ontology Language (OWL). Additionally, we use HECON as a framework to create a Knowledge
Graph using the health evolution database built in [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ].
      </p>
      <p>Our main contributions are:
• A model for representing and reasoning about the evolution of health events over time:</p>
      <p>HECON - Health Condition Evolution Ontology.
• A Knowledge Graph that defines an abstraction of the available data about health evolution.</p>
      <p>Moreover, it also includes information that extends the clinical concepts descriptions
provided by SNOMED CT taxonomy.
• A set of SPARQL queries for validation and guidance to users of both the ontology and
the Knowledge Graph.</p>
      <p>The rest of the paper is organised as follows. Section 2, describes the background and
motivating scenario. In Section 3, we review the literature on the use of healthcare ontologies,
and health evolution databases. Section 4 details the methodology used to build the ontology and
Section 5 states the knowledge requirements that HECON should address. Section 6 describes
the development process of HECON. In Section 7 we present the Knowledge Graph and the
evaluation of the ontology. Finally, in Section 8, we summarise the conclusions and describe
future directions of the research.</p>
      <p>3FHIR terminology defines condition as ‘A clinical condition, problem, diagnosis, or other event, situation, issue, or
clinical concept that has risen to a level of concern.’ see http:// hl7.org/ fhir/ condition.html</p>
      <p>4HECON Ontology repository https://github.com/albamoralest/HECON-Ontology and BioPortal https://
bioportal.bioontology.org/ontologies/HECON</p>
    </sec>
    <sec id="sec-3">
      <title>2. Background and motivation</title>
      <p>
        First responders attending an emergency should have an overview of the situation before
performing any operation. One of their first tasks is to retrieve information about the type
of event, the people involved and details of the premises. During a fire emergency, additional
information such as people’s health conditions or disabilities can assist first responders in
making decisions for rescue operations [
        <xref ref-type="bibr" rid="ref11">11</xref>
        ]. This information usually is retrieved from people
on the scene or fire wardens.
      </p>
      <p>
        We examine the scenario of a fire event in a large organisation in the UK. In a large
organisation, an Access Control System (ACS) holds information of people entering the building as they
use their magnetic cards to gain access, while visitors register (and obtain their cards) at the
reception desk. The organisation adheres to general guidelines and procedures in case of an
emergency; for example, the UK Government regulated guidance for emergency preparedness
[
        <xref ref-type="bibr" rid="ref12 ref13">12, 13</xref>
        ]. In relation to fire emergencies, the guidelines indicate that a person should notify any
disability or health issue that may afect them during an evacuation to their line manager and
discuss the elaboration of a Personal Emergency Evacuation Plan (PEEP), together with the
Health &amp; Safety Unit [
        <xref ref-type="bibr" rid="ref12">12</xref>
        ]. The PEEP is an elaborated plan that thoroughly explains the type of
support a person should have to leave the premises, and it is tailored according to the person’s
capabilities. Crucially, the PEEP form collects employees’ personal information about their
health conditions and disabilities. However, several issues arise from the stated scenario:
• Although the procedures state the PEEP should be updated regularly, employees’ most
recent health events might not be recorded immediately, particularly in large organisations.
As a result, emergency responders could question the completeness and accuracy of the
information.
• Employees might choose not to disclose sensitive information or consider their health
issues irrelevant, which leads to incomplete PEEP records. A clear example is an
’obstructive bronchitis’ condition. Although it is not a permanent disability, typical symptoms
include dificulty breathing and walking. If the issue is recent, symptoms are relatively
acute and may lead to a vulnerable situation.
• Although general evacuation plans are put in place for visitors, it may be possible that
guests do not provide suficient information about their state of health; hence information
might be incomplete.
      </p>
      <p>
        Typically, if a fire starts, the Health &amp; Safety Unit should recover the PEEPs to assist the
emergency responders in identifying people in need of special assistance. However, a Smart
City perspective could open opportunities to streamline this process. First, when the fire starts,
the building’s Access Control System (ACS) could identify the people in the building. Second,
an intelligent system capable of automatically retrieving the information from the ACS and
access health records from the National Health Service (NHS) could automatically analyse and
extract updated information regarding people’s ongoing health issues. Since health records hold
granular information of a person’s health condition, a challenging area of study is extracting
helpful information that reports on a person’s current medical status [
        <xref ref-type="bibr" rid="ref8 ref9">9, 8</xref>
        ].
      </p>
      <p>
        Hence, the analysis of health conditions is not a straightforward process. In [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ] we introduced
the concept of Health Evolution Statement (HES) to solve the problem of representing and
reasoning over the person’s state of health at a given point in time. The HES is an elaborated
representation of the health recovery process, which describes two main characteristics of health
evolution: the way it develops and its estimated duration. Specifically, the HES representation
can express whether a condition improves or declines, how long it takes for a person to recover,
and whether the condition is chronic. Crucially, a system using this model will automatically
detect ongoing health events at the time of the emergency. To the best of our knowledge, no
existing ontology is tailored to the representation of health evolution over time. The same
applies to existing, reusable knowledge bases in healthcare.
      </p>
    </sec>
    <sec id="sec-4">
      <title>3. Related Work</title>
      <p>In this section, we revise related work in health evolution representation using ontologies,
SNOMED CT applications and access to databases related to healthcare convalescence time.</p>
      <p>
        Ontologies are largely used in applications in the Semantic Web field and are widely adopted
in Knowledge Engineering in various domains. Uschold and Grüninguer [
        <xref ref-type="bibr" rid="ref14">14</xref>
        ] proposed the
ifrst guidelines for building ontologies. Furthermore, methodological frameworks like [
        <xref ref-type="bibr" rid="ref15 ref16">15, 16</xref>
        ]
also cover aspects of the ontology development process, life cycle, methods and techniques.
For instance, the NeOn Methodology [
        <xref ref-type="bibr" rid="ref17">17</xref>
        ] proposes a more flexible approach with particular
attention to ‘ontology engineering by reuse’ and collaborative development. Our methodology
follows these established frameworks and adapts the diferent steps from each methodology
according to our system and knowledge requirements in the emergency response domain. For
instance, we follow [
        <xref ref-type="bibr" rid="ref14 ref18">18, 14</xref>
        ] to identify the purpose of the ontology, the motivating scenario and
to capture knowledge requirements expressed as Competency Questions. Moreover, we follow
best practices of reusing established ontologies to minimise the addition of new ontology terms
[
        <xref ref-type="bibr" rid="ref17">17</xref>
        ].
      </p>
      <p>
        In the context of emergency support, well-structured information, readily available and
pertinent to first responders’ needs [
        <xref ref-type="bibr" rid="ref11">11</xref>
        ] is a valuable asset and a life-saving resource during
an emergency event. The adoption of Electronic Health Records (EHRs) and related standards
(SNOMED CT and FHIR) for collecting and exchanging healthcare data has leveraged the
development of intelligent systems and ontologies for emergency support [
        <xref ref-type="bibr" rid="ref19">19</xref>
        ] that provide
information fit for emergency services requirements. Research to date confirms that most
knowledge-based applications are oriented to solving issues related to the semantic integration
of heterogeneous healthcare data, particularly in crisis management scenarios [
        <xref ref-type="bibr" rid="ref20">20</xref>
        ]. Although
these proposed systems focus on supporting emergency services using healthcare-related data,
no applications have included the representation of knowledge about health events’ evolution
over time in the context of emergency response. This paper proposes an ontology as a formal
representation of health evolution capable of identifying and reasoning upon conditions that
could afect a patient’s condition at the time of an emergency.
      </p>
      <p>
        With respect to EHRs data handling and exchange, an important aspect is the
standardised representation of clinical terminology. SNOMED CT, the Systematised Nomenclature of
Medicine Clinical Terms is one of the most used schemes. It comprises medical terms such
as disorders, procedures, body structures and other clinical findings. Other schemes such as
ICD-10 (International Classification of Diseases) and LOINC (Logical Observation Identifiers,
Names, and Codes) [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ] focus on terminology for reporting and monitoring diseases and clinical
measurement terms, respectively. However, these taxonomies do not include definitions or
information about health evolution, revealing the need for reliable and structured information
that describes health issues’ convalescence time and recovery. As part of our research, we
represent the database of health evolution built previously in [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ] as a Knowledge Graph following
a Linked Data approach. Furthermore, we expand the specification of SNOMED CT by directly
using SNOMED URIs in the KG.
      </p>
      <p>In conclusion, the analysis of the literature indicates that, despite a substantial body of
research related to the use of healthcare data, there remains an evident opportunity to develop
additional resources for the benefit of emergency teams tackling emergency events.</p>
    </sec>
    <sec id="sec-5">
      <title>4. Methodology</title>
      <p>
        In Section 2 we described the challenges found to extract relevant information from health
records specifically to support emergency responders. Our eforts focus on providing an
intelligent system with a model that allows the automatic evaluation of people’s health conditions. In
what follows, we describe the methodology used to develop the Health Condition Evolution
Ontology (HECON), which is our proposed model for representing the evolution of health
events over time and facilitating a system’s reasoning on health records. We follow ontology
engineering good practices and methodologies [
        <xref ref-type="bibr" rid="ref14 ref16 ref17">14, 16, 17</xref>
        ], and devise the following phases:
Abstracting the scenario. In this phase, we identify the scope and purpose of our ontology.
The main goal of our ontology is to provide an Intelligent System with enough knowledge
allowing the detection of ongoing health issues using health records as data source. We use the
scenario described in Section 2 as a guide for identifying key ontology concepts and relationships
that define ‘health evolution’ terms. Additionally, we identify data sources of condition evolution,
for example, descriptions of health conditions.
      </p>
      <sec id="sec-5-1">
        <title>Identify knowledge requirements and formulate Competency Questions (CQs). The</title>
        <p>second phase is dedicated to identifying the knowledge requirements of a system that accesses
health records to assess a person’s state of health. We express the requirements in the form of
Competency Questions (CQs). The CQs will guide the ontology development process, providing
the main framework to evaluate the expressiveness of the ontology and the completeness of the
related knowledge graph (its ability to answer the questions on specific health records).
Ontology design and construction. This phase consists of two tasks: a) describe the
concepts and relations that constitute the ontology, and b) use the vocabulary compiled in a) to
express the ontology in a formal language. We build the ontology using Protégé ontology editor
and specify its terms with the Web Ontology Language (OWL). This phase also contemplates
the addition of the axioms expressing the relationships and constraints among the ontology
entities. Similarly, during this phase, we identify the established ontologies for reuse and define
how to integrate these concepts in HECON.</p>
        <p>
          Knowledge Graph population The fourth phase is dedicated to building the Knowledge
Graph (KG). First, we use the data sources identified in the first phase to build a structured
database of Health Evolution Statements (HES) as detailed in our previous study in [
          <xref ref-type="bibr" rid="ref8">8</xref>
          ]. We use
SPARQL Anything [
          <xref ref-type="bibr" rid="ref21">21</xref>
          ], to generate RDF data from HES database, store our KG and evaluate
the CQs in the next phase.
        </p>
        <p>
          Ontology validation. The last phase concerns to the evaluation of the ontology. We consider
two aspects: the consistency of the ontology and the fulfilment of the CQs. We use the Hermit
reasoner [
          <xref ref-type="bibr" rid="ref22">22</xref>
          ] provided in Protégé to check ontology consistency with respect to the semantics of
OWL. In this phase we use the KG built in the previous phase and a dataset of Synthetic Health
records [23]. We translate the CQs into SPARQL queries and use them to interrogate the ontology.
We compare the results from the query execution with the expected values. CQ fulfilment
indicates that the ontology satisfies the system requirements. In case of inconsistencies, we
repeat the process to clarify the SPARQL queries or fix the ontology.
        </p>
      </sec>
    </sec>
    <sec id="sec-6">
      <title>5. Requirements</title>
      <p>In this section, we extract the knowledge requirements from the perspective of a system that
handles the scenario proposed in Section 2.</p>
      <p>In our scenario, we described a fire emergency in a large organisation. In the context of
a Smart City, an intelligent system can leverage the organisation’s Access Control System
(ACS) to determine the people (employees and visitors) in the building at the moment of the
emergency. The ACS provides the list of people in the building, and therefore, the healthcare
provider can retrieve their electronic health records. The public health provider uses SNOMED
CT and FHIR as standards for accessing and exchanging EHRs. The intelligent system uses
people’s healthcare data to identify up-to-date health issues. The main question that our system
should answer using the ontology is: What is the current ‘state of health’ of a person at a certain
point in time? Building around the described scenario and this central question, we express the
knowledge requirements as a set of Competency Questions (CQs) that our proposed ontology
should answer. The CQs are expressed as follows:
• CQ1: What is the health evolution information of a given SNOMED concept?
• CQ2: How does a given condition evolve over time?
• CQ3: What is the pace at which a given SNOMED concept evolve?
• CQ4: What are the expected minimum and maximum recovery times for a given SNOMED
concept?
• CQ5: If an emergency happens after the expected maximum recovery time, is a condition
still ongoing?
• CQ6: If an emergency happens before the expected minimum recovery time, is a condition
still ongoing?
• CQ7: If an emergency happens between the expected minimum and maximum recovery
time, is a condition still ongoing?
The data used to build the database of health evolution is retrieved from diferent sources,
identified in phase one of our methodology. These include two authoritative and reliable
data sources: NHS England5 and MAYO Clinic6. Consequently, we consider it essential to</p>
      <sec id="sec-6-1">
        <title>5https://www.nhs.uk/conditions/</title>
        <p>6https://www.mayoclinic.org/diseases-conditions
represent this knowledge by including the associated source and explaining the context on how
information was generated. We express these requirements as follows:
• CQ8: What method generates specific health evolution information of a given SNOMED</p>
        <p>
          CT concept (e.g., user study, automatic knowledge extraction)?
• CQ9: What is the source of the health evolution information (e.g., authoritative sources,
domain experts)?
• CQ10: What/Who is the organisation/person providing this information?
• CQ11: Is there additional information indicating the information’s quality?
Although the example in this paper relates to a fire emergency, the ontology is generic and
can support other types of emergencies, leaving the assessment of how the condition has to be
handled to the emergency support system relying on it (see [
          <xref ref-type="bibr" rid="ref8">8</xref>
          ]). Handling privacy requirements
is not part of the ontology, however our approach assures that EHR shared are adequate, relevant
and limited to the intended use (data minimisation GDPR principle), these aspects are discussed
in [
          <xref ref-type="bibr" rid="ref9">9</xref>
          ]. In addition, we consider relevant to describe the design constraints derived from the
scope of our system and best ontology engineering practices:
• Reuse established ontologies when possible, minimising the addition of new ontology
terms. In our case, to represent the time duration, we utilise the Time Ontology [24] and
PROV Ontology [25] for provenance information.
• Reuse standards in the health domain. We link the condition evolution information to
SNOMED CT, a comprehensive collection of healthcare terminology. We also use the
FHIR standard to represent the information of our synthetic dataset and facilitate the
management of health-related data.
        </p>
      </sec>
    </sec>
    <sec id="sec-7">
      <title>6. HECON’s Ontology</title>
      <p>In what follows, we describe the core concepts of the HECON Ontology and the integration of
SNOMED CT clinical terms. Next, we explain how we incorporate Time [24] and PROV-O [25]
Ontologies and their role in our model.</p>
      <sec id="sec-7-1">
        <title>6.1. HECON core concepts</title>
        <p>
          We define a number of ontological concepts to represent health evolution (Fig. 1). First, we
define an Health Evolution Statement (HES) as an abstraction of the components that indicate
the recovery process [
          <xref ref-type="bibr" rid="ref8">8</xref>
          ]; its main elements are: the types of health evolution, the velocity at
which it changes, and its duration. We identify four main types of health evolution:
• Improvement - the evolution is favourable and indicates recovery of good health.
• Decline - the evolution is adverse and gradually becomes worse during time.
• Permanent - indicates a persistent condition.
• Unafected - describes a health condition or SNOMED CT concepts with no efect on
state of health, for example, blood test or administrative procedures.
        </p>
        <p>We use Progress to represent type of events that evolve over time. These types of events,
Improvement and Decline, have pace and an estimate of their duration. For instance, a
‘Fracture of ankle’ event gets better after a period of time, its evolution type is ‘Improvement’.
The velocity at which a health event evolves is represented by Pace and could take values such as
FAST, MODERATE and SLOW. The estimated duration is defined by has minimum and maximum
duration. These two boundaries (min and max duration) express time extent, and could take any
numerical value in minutes, hours, days, weeks, months or years; we represent these elements
with time:Duration and properties time:numericDuration, time:unitType from the Time
Ontology (see Table 1 for more examples). Health events are represented in health records using
a standard terminology system; in our case, SNOMED CT scheme. Therefore, each expression
of health evolution is linked (has a SNOMED CT concept identifier ) to its corresponding term in
the SNOMED CT taxonomy. We extend SNOMED CT by directly using SNOMED namespace
URI &lt;http://snomed.info/id/&gt;. For example, a health event such as ‘Fracture of ankle’ is
represented as follows: http://snomed.info/id/16114001.</p>
        <p>
          A system using HECON can predict whether a health condition is still ongoing by calculating
the time that has passed between the date it was recorded (in a health record) and its estimated
recovery date (the minimum and maximum duration). For example, an ankle fracture (see
Table 1) that has not reached its minimum duration is more likely to impact a person’s health
condition than if the same event happened two months ago (max. duration). The type of health
evolution also influences the impact on patient’s state of health; a condition that improves is
diferent from one that is permanent, as described in [
          <xref ref-type="bibr" rid="ref8">8</xref>
          ].
        </p>
      </sec>
      <sec id="sec-7-2">
        <title>6.2. Provenance representation</title>
        <p>Part of the requirements state the necessity to provide context on how the Health Evolution
Statement (HES) was generated, the data sources used and the organisations or persons supporting
this information (Fig. 2).</p>
        <p>We use PROV-O basic classes and properties to represent the origin of each HES. A SNOMED
CT concept can be linked to none or many Health Evolution Statements. Each HES is a subclass
of prov:Entity that was generated (prov:wasGeneratedBy) using one or many approaches or
activities - prov:Activity. We describe three possible activities:
Knowledge extraction - the health evolution data was built using knowledge acquisition
techniques for extracting information from unstructured data sources. Therefore, every HES
generated have data properties confidence and support. For example, the HES ‘Improvement
Moderate from 8 days to 2 months’ for Fracture of ankle (sct:16114001) was generated by the
’KnowledgeExtraction’ activity, and its support value is ’0.0016’.</p>
        <p>
          Rule execution - the health evolution data was generated as a result of a knowledge
completion process (as described in detail in [
          <xref ref-type="bibr" rid="ref8">8</xref>
          ]). We apply a set of rules (based on the relationships
and attributes in SNOMED CT taxonomy) that indicate a ’target’ SNOMED CT concept that can
inherit the same HES as another SNOMED CT ’source’ concept that already has a HES. The
relation between RuleExecution and SNOMEC CT concept is expressed as hasSctTargetConcept
and hasSctSourceConcept respectively. We complement information about this activity with the
data property ruleSyntax. For instance, the HES ’Improvement Slow from 2 months to 6 months’
for Bacterial sinusitis (sct:703470001) was generated by the ’RuleExecution’ activity. It has as
source concept ’Sinusitis’ (sct:36971009) and target concept Bacterial sinusitis (sct:703470001).
User study - in this case, the HES is the result of a manual evaluation that checks the accuracy
of the current database or collects new HESs. This type of activity is carried out with the support
of domain experts (e.g., doctors, nurses, emergency responders). This activity also provides
data on the agreement between compiled responses in terms of an agreeementValue.
        </p>
        <p>An activity, for example, Knowledge Extraction, can use one or multiple Sources. A source
(prov:Entity) at the same time has a Provider, this could be an organisation or a person, for
example: NHS England, or a domain expert. Some sources optionally include details of public
URL or exact text that generated the HES, expressed with data properties url and sentence.
Following the previous example of ’Fracture of ankle’, we can express that it was derived from
’Public Web Sources’ and its provider is ’MAYO Clinic’. It is possible to represent all the possible
Sources used by a certain activity with the property prov:Used.</p>
      </sec>
    </sec>
    <sec id="sec-8">
      <title>7. Knowledge Graph</title>
      <p>In this section, we give a brief description of the data source collection, and then we describe
the process followed to build the Knowledge Graph.</p>
      <p>
        First, as data input, we use the database of Health Condition Evolution (HES) we built in
the context of our previous study [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ]. The data was collected from reliable public sources
(MAYO Clinic and NHS England). We relied on knowledge acquisition techniques such as
Machine Learning (ML) and built a semi-automatic supervised classification pipeline to extract
information from unstructured data. The database is a collection of Health Condition Statements;
each statement is a structured representation of how a health event evolves. For example, the
expression: ‘...it takes 2 to 3 weeks to recover completely.’ is represented as Improvement Moderate
from 2 weeks to 3 months. Each HES is linked to a health condition represented as a SNOMED
CT concept identifier. A condition, now formally a SNOMED CT concept, could be connected
to one or more HES. Additionally, the database contains information about the sources used
to generate each HES. The database of HES is the result of the various knowledge acquisition
pipelines (processes described in [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ]), the output is a set of CSV files which we use to generate
the KG.
      </p>
      <p>
        Second, we used SPARQL Anything [
        <xref ref-type="bibr" rid="ref21">21</xref>
        ], a system that allows to generate RDF data from
diferent types of formats with plain SPARQL CONSTRUCT queries 7. Next, we store RDF data
in TTL data format. Finally, we use the Blazegraph database to store our KG and evaluate the
CQs by executing SPARQL queries on the data.
      </p>
      <sec id="sec-8-1">
        <title>7.1. Data statistics</title>
        <p>The resulting Knowledge Graph contains 5,446,510 triples and 33,828 unique SNOMED CT
concepts. A SNOMED CT concept is linked to one or more HESs using the corresponding
SNOMED CT identifier. Table 2 presents the summary statistics for each OWL class. The
number of SNOMED CT concepts represented in our KG is approximately 10% of the total of
concepts in the SNOMED CT taxonomy. We are currently working on a user study, with domain
experts advice, to validate the current knowledge acquisition pipeline.</p>
      </sec>
      <sec id="sec-8-2">
        <title>7.2. Evaluation</title>
        <p>Our objective is to formally represent how health events evolve over time and, crucially, meet
the knowledge requirements of an intelligent system that automatically detects ongoing health
issues at the time of an emergency, for example, a fire event. We built the HECON Ontology
following the list of knowledge requirements collected in Section 5.</p>
        <p>
          We use Protégé and the Hermit reasoner to check the formal consistency of the ontology.
The final KG represents a large amount of data, therefore, to make the evaluation practicable,
we based the consistency check on a random data sample. In order to evaluate the expressivity
of the ontology and the completeness (fitness for use) of the related KG for our task, we encode
the Competency Questions (CQs) listed in Section 5 into SPARQL queries. We use the same
dataset of patients’ synthetic health records used in [
          <xref ref-type="bibr" rid="ref8">8</xref>
          ] and compare the outcome of the queries
against the expected results. The dataset is described using FHIR and SNOMED CT standards,
emulating UK national information standards requirements and therefore we make sure our
        </p>
        <sec id="sec-8-2-1">
          <title>7All the queries and results are available in the HECON repository</title>
          <p>approach is compliant with real implementations. In what follows, we group closely related
CQs to give a description of the evaluation process and the results.</p>
          <p>Competency Questions one to four (CQ1 to CQ4). These competency questions inquire
about the duration, pace and type of change characterising the evolution of a condition. As
described in Section 6 the Health Evolution Statement is a compilation of three pieces of
information: type of event (classes: Improvement, Decline, Permanent or Unafected), pace
(Slow, Moderate or Fast) and time range (minimum and maximum duration). By retrieving the
type of event (CQ2), the pace (CQ3) and the expected recovery time (CQ4), we can satisfy CQ1,
as shown in Fig.3. For example, if we find in the health records an event such as ’Broken leg’,
the answer will be a list of HES linked to the associated SNOMED CT concept, as shown in
Fig. 4. These results will be used by an intelligent system to assess the validity of the given
condition.</p>
        </sec>
      </sec>
      <sec id="sec-8-3">
        <title>Competency Questions five to seven (CQ5 to CQ7). For CQs five to seven, we encode a</title>
        <p>
          SPARQL query that retrieves the maximum and minimum duration of a condition in a health
record (as shown in Fig.5a). For this example, we set the date the fire started as ‘2019-10-16’
and obtain the number of days in between the start of the health event and the fire event. The
query also retrieves the minimum and maximum duration, which allows the intelligent system
to infer if the health event is still ongoing, as detailed in [
          <xref ref-type="bibr" rid="ref8">8</xref>
          ]. We perform the test multiple times
with diferent reference dates; the queries and results are available in the HECON repository.
        </p>
      </sec>
      <sec id="sec-8-4">
        <title>Competency Questions eight to eleven (CQ8 to CQ11). Finally, we consider CQs that</title>
        <p>are related to provenance information. We encode the query (as shown in Fig.5b) and retrieve
the Activity (CQ8), the Source (CQ9) and the Provider (CQ10) that support the value of HES for
a given SNOMED CT concept. The query results are displayed in Fig. 6.</p>
        <p>
          In summary, these results show that the HECON Ontology allows us to represent and access
knowledge about the evolution of conditions recorded in health records. We selected a random
sample of health records and queried their HES using HECON and the KG. We were able to
replicate the results obtained in [
          <xref ref-type="bibr" rid="ref8">8</xref>
          ], therefore meeting our requirements successfully.
(a) CQs: 5-7.
        </p>
        <p>(b) CQ: 8-11.</p>
      </sec>
    </sec>
    <sec id="sec-9">
      <title>8. Conclusions and Future work</title>
      <p>In this paper, we presented HECON - Health Condition Evolution Ontology, a formal model for
representing and reasoning on health events evolution over time. We presented our approach
as an important tool to address the knowledge requirements of an intelligent system that
automatically estimates a person’s current state of health in the context of a fire emergency.</p>
      <p>An essential contribution of our work refers to the Knowledge Graph of Health Condition
Evolution. We identified that structured information about health condition’s evolution is not
readily accessible. By following a Linked Data approach we provide a structured database of
conditions’ evolution over time, which is easy to access and fit to out system requirements.</p>
      <p>Here, we focused on the ontology and the knowledge graph, leaving the quality evaluation of
the knowledge acquisition processes to future work. The review and validation of the automatic
data construction with domain experts’ help are essential; it will extend SNOMED CT coverage
and ultimately improve the identification of ongoing health events.
[23] J. Walonoski, M. Kramer, J. Nichols, A. Quina, C. Moesel, D. Hall, C. Dufett, K. Dube,
T. Gallagher, S. McLachlan, Synthea: An approach, method, and software mechanism for
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[24] J. R. Hobbs, P. Feng, Time ontology in OWL, 2006. URL: https://www.w3.org/TR/owl-time/.
[25] T. Lebo, S. Sahoo, D. McGuinness, K. Belhajjame, J. Cheney, D. Corsar, D. Garijo, S.
SoilandReyes, S. Zednik, J. Zhao, PROV-O:The PROV ontology (2013).</p>
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