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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>Innovative Paradigms for Supporting Privacy-Preserving Multidimensional Big Healthcare Data Management and Analytics: The Case of the EU H2020 QUALITOP Research Pro ject</article-title>
      </title-group>
      <contrib-group>
        <aff id="aff0">
          <label>0</label>
          <institution>LORIA</institution>
          ,
          <addr-line>Nancy</addr-line>
          ,
          <country country="FR">France</country>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>iDEA Lab, University of Calabria</institution>
          ,
          <addr-line>Rende</addr-line>
          ,
          <country country="IT">Italy</country>
        </aff>
      </contrib-group>
      <abstract>
        <p>QUALITOP is an authoritative EU H2020 research project whose main goal consists in supporting big data management, analytics and predictive analytics over cancer patients treated by the innovative immunotherapy therapeutic approach, in order to study and support decision making processes about their Quality of Life (QoL). Within the QUALITOP big data lake, a critical requirement consists in supporting privacy-preserving multidimensional big healthcare data management and analytics, which is addressed via innovative paradigms. This paper presents some relevant innovations developed in the context of the latter research area, as contextualized to the QUALITOP project, with also an overview of possible research challenges for future eforts in the investigated field.</p>
      </abstract>
      <kwd-group>
        <kwd>Big Data Management</kwd>
        <kwd>Big Data Analytics</kwd>
        <kwd>PrivacyPreserving Big Data Management</kwd>
        <kwd>Privacy-Preserving Big Data Analytics</kwd>
        <kwd>Privacy-Preserving Multidimensional Big Data Management and Analytics</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>-</title>
      <p>
        Nowadays, big healthcare data management and analytics [
        <xref ref-type="bibr" rid="ref22 ref3">22, 3</xref>
        ] are playing the
leading role within the broad context of big data applications and systems (e.g.,
[
        <xref ref-type="bibr" rid="ref2 ref21 ref4 ref5">5, 21, 4, 2</xref>
        ]). A clear example is represented by the modern COVID-19 outbreak
that is spreading world-wide at an impressive rate. Here, healthcare analytics
is critical for taking medical decision making at Country- and Regional-level,
thus determining the desired healthcare policy. Monitoring multidimensional
aspects of QUAlity of Life after cancer ImmunoTherapy - an Open smart
digital Platform for personalized prevention and patient management
(QUALITOP)[
        <xref ref-type="bibr" rid="ref1">1</xref>
        ] is an authoritative EU H2020 research project in this context. Within
the QUALITOP project, a critical challenge is represented by the issue of
providing support for privacy-preserving multidimensional big healthcare data
management and analytics, where the main emphasis is on the two following keywords:
multidimensionality [
        <xref ref-type="bibr" rid="ref16">16</xref>
        ] and privacy preservation [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ]. In this paper, we present
some relevant innovations developed in the context of the latter research area,
as contextualized to the QUALITOP project, with also an overview of possible
research challenges for future eforts in the investigated field.
2
      </p>
    </sec>
    <sec id="sec-2">
      <title>The EU H2020 QUALITOP Research Project</title>
      <p>QUALITOP aims at developing a European immunotherapy-specicfi open Smart
Digital Platform and using big data analysis, artificial intelligence, and
simulation modelling approaches. This approach enables collecting and aggregating
eficiently real-world data to monitor health status and Quality of Life (QoL) of
cancer patients given immunotherapy. Through causal inference analyses,
QUALITOP identifies the determinants of health status regarding
ImmunotherapyRelated Adverse Events (IR-AEs) and defines patient profiles in a real-world
context. For this, heterogeneous data sources (big data), both retrospective and
prospective –collected for QUALITOP from clinical centres in four EU
countries— integrate lifestyle, genetic, and psycho-social determinants of QoL. Using
machine learning approaches, QUALITOP provides “real-time”
recommendations stemming from patient prolfies and feedbacks via the Smart Digital
Platform. Furthermore, an increased visibility on patients’ behaviour, a better
IRAEs prediction, and an improvement of care coordination help analysing through
simulation modelling approaches, can be gained in cost-efectiveness. Guidelines
are issued over the short and long-term.</p>
      <p>The QUALITOP consortium is the following:
11. University Medical Center Groningen (UMCG), The Netherlands;
12. Massachusetts General Hospital (MGH), United States;
13. University of Calabria (UNICAL), Italy.
3</p>
    </sec>
    <sec id="sec-3">
      <title>Privacy-Preserving Multidimensional Big Data</title>
    </sec>
    <sec id="sec-4">
      <title>Management and Analytics within the QUALITOP</title>
    </sec>
    <sec id="sec-5">
      <title>Big Data Lake</title>
      <p>One essential component of the QUALITOP platform is represented by its big
data lake. The QUALITOP big data lake is populated by big healthcare data
coming from the reference data sources, and it supports both big data
management and analytics procedures over them.</p>
      <p>
        One critical aspect of the QUALITOP big data lake consists in ensuring
the privacy of big healthcare data during the management and analytics tasks,
as highlighted by several studies (e.g., [
        <xref ref-type="bibr" rid="ref17 ref6">6, 17</xref>
        ]). Consider Figure 1. Here, the
QUALITOP big data lake is shown, with the detail on the Privacy-Preserving
Data Publishing (PPDP) module.
      </p>
      <p>
        Within the PPDP module, several techniques for ensuring the privacy of
big healthcare data are implemented. Among all alternatives, the choice is set
on the so-called privacy-preserving multidimensional big data management and
analytics techniques (e.g., [
        <xref ref-type="bibr" rid="ref15 ref8 ref9">9, 8, 15</xref>
        ]). Basically, these techniques extend the
wellunderstood privacy-preserving OLAP paradigm (e.g., [
        <xref ref-type="bibr" rid="ref10 ref11 ref13 ref14">14, 13, 11, 10</xref>
        ]) to the
innovative context of big data management and analytics.
      </p>
      <p>
        Privacy-preserving multidimensional big data management and analytics
predicates a collection of models, techniques and algorithms for making
privacypreserving data cubes on top of which management and analytics tasks are
executed. This can be obtained, for instance, according to diferent alternatives:
1. SPPOLAP algorithm [
        <xref ref-type="bibr" rid="ref13 ref14">14, 13</xref>
        ], which introduces the two following main
innovations: (i ) a novel privacy OLAP notion; (ii ) flexible adoption of
samplingbased techniques in order to achieve the final privacy-preserving data cube;
2. SDO algorithm [
        <xref ref-type="bibr" rid="ref10 ref11">11, 10</xref>
        ], which introduces the novel concept of the
socalled secure distributed OLAP aggregation task – basically, this task purses
the idea of performing OLAP across multiple distributed SUM-based
twodimensional OLAP views extracted from data cubes under the Secure
Multiparty Computation (SMC) requirements, by relaying on powerful CUR-based
matrix decomposition methods used as a fundamental privacy-preserving tool
[
        <xref ref-type="bibr" rid="ref12">12</xref>
        ].
      </p>
      <p>
        Thanks to these fundamental algorithms, efective and eficient
privacypreserving multidimensional big data management and analytics can be obtained
within the QUALITOP big data lake, obviously by taking into consideration the
special features of big data processing (e.g., [
        <xref ref-type="bibr" rid="ref25">25</xref>
        ]), being high-performance
computing and fast data availability two of the main research challenges among
them.
4
      </p>
    </sec>
    <sec id="sec-6">
      <title>Privacy-Preserving Big Data Management and</title>
    </sec>
    <sec id="sec-7">
      <title>Analytics: Future Research Challenges</title>
      <p>
        With the impressive growth of big data and Cloud-based technologies, the need
for privacy-preserving methodologies will be more and more relevant in both
academic and industrial research, specially driven by modern ICT challenges of
next-generation societies (e.g., social media, health intelligence, smart cities, and
so forth). Among these challenges, we retain the following as the most relevant
ones:
1. Integration with Cryptographic Techniques One of the most
important challenge today is represented by integration of privacy-preserving
approaches with traditional cryptographic techniques, as emerging in the last
research trends (e.g., [
        <xref ref-type="bibr" rid="ref18 ref23">23, 18</xref>
        ]).
2. Balancing Accuracy and Privacy When dealing with analytics tools
over big data, accuracy must be balanced with privacy (e.g., [
        <xref ref-type="bibr" rid="ref13 ref19">13, 19</xref>
        ]). Indeed,
accuracy and privacy are two contrasting properties: when accuracy increases
then privacy decreases, and viceversa. Therefore, in many contexts (e.g.,
healthcare analytics), intelligent tools must balance accuracy and privacy, in
order to obtain good prediction performance at the cost of a safe privacy of
data.
3. Inference Control Techniques Inference methods (e.g., [
        <xref ref-type="bibr" rid="ref20 ref24">24, 20</xref>
        ]) can still
violate privacy of data when all (privacy-preserving) countermeasures are
taken. For instance, query inference is a popular technique that allows
us to derive (unknown) answers (or, approximate answers) to un-granted
queries from (known) answers to granted queries. Next-generation
privacypreserving techniques must deal with this emerging issue, thus devising
innovative inference-control privacy preserving big data management and
analytics approaches.
5
      </p>
    </sec>
    <sec id="sec-8">
      <title>Conclusions and Future Work</title>
      <p>Starting from the context of the EU H2020 QUALITOP research project, this
paper has presented some of the privacy-preserving multidimensional big data
analytics techniques implemented within the big data lake of the reference
platform. In addition to this, an overview of possible research challenges for future
eforts in the investigated field has been proposed.</p>
      <p>Future work is mostly oriented towards achieving the integration of
privacypreserving multidimensional big data analytics techniques with emerging
machine-learning-based advanced analytical tools, such as tensors.</p>
    </sec>
    <sec id="sec-9">
      <title>Acknowledgements References</title>
      <p>This research has been supported by the EU H2020 QUALITOP research
project, H2020 Project ID: 875171.</p>
    </sec>
  </body>
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