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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>Industrial Geological Information Capture with GeoStructure Ontology</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Yuanwei Qu</string-name>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Baifan Zhou</string-name>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Evgeny Kharlamov</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Martin Giese</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Bosch Center for AI</institution>
          ,
          <country country="DE">Germany</country>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>Department of Informatics, University of Oslo</institution>
          ,
          <country country="NO">Norway</country>
        </aff>
      </contrib-group>
      <abstract>
        <p>Understanding geological structures plays an essential role in a wide range of industries. Various tools and software have been developed to support the observation and characterisation of the geological structures and they produce a large volume of heterogeneous data. Thanks to the development of semantic technologies, plenty of works have investigated industrial geological data. In contrast, geological sketches, ifgure interpretations, and illustrations as the initial data collection and analysis steps have received little attention. Most structure information is still reported as PDF files with forms, tables, and raster images with interpretations. We attempt to fill this gap by providing an ontology-based industrial geological information capture method to allow users to input and store structure information formally. Following users' sketches, the corresponding knowledge graphs will be generated. This work aims to make the ifrst-hand geological structure information findable, accessible, interoperable, reusable (FAIR), and to support qualitative information reasoning, from a user-driven perspective, and to meet the needs of digitised industry.</p>
      </abstract>
      <kwd-group>
        <kwd>eol&gt;Geological information capture</kwd>
        <kwd>Information modelling</kwd>
        <kwd>Ontology engineering</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <p>
        Many industries that nowadays serve as foundations of our society greatly rely on a solid
understanding of geological structures, such as petroleum [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ], mining [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ], sustainable energy [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ],
and construction industries [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ]. Geologists use sketches to, e.g., assist hydrocarbon exploration
in the petroleum industry [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ], to study regional geological structures in the mining industry [
        <xref ref-type="bibr" rid="ref6">6</xref>
        ],
and to to evaluate fluid injection, transport, and storage in the sustainable energy industry [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ].
      </p>
      <p>
        Drawing sketches plays an essential role in representing geologists’ understanding and
conceptualisation of geological structures of the domain [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ]. The sketching refers to the
process where relevant geological entities from the field will be presented with certain graphical
elements, while irrelevant entities will be abandoned [
        <xref ref-type="bibr" rid="ref9">9</xref>
        ], based on geologists’ domain knowledge.
As such a basic but essential knowledge sharing and recording method, sketching has been
widely adopted by geology from the starting point of this domain. It is considered as a primary
and necessary method to assist the geological study [
        <xref ref-type="bibr" rid="ref10">10</xref>
        ].
      </p>
      <p>
        Though pen and paper are still geologists’ good friends, the need of digitising the
geoknowledge, allowing geologists to express knowledge in a machine-readable way and improving
data interoperability has increased significantly. In the geology community and industries,
digitisation is drawing significant attention in activities such as ontological modelling [
        <xref ref-type="bibr" rid="ref11 ref12">11, 12</xref>
        ],
reasoning [
        <xref ref-type="bibr" rid="ref13 ref14">13, 14</xref>
        ], knowledge graph construction [
        <xref ref-type="bibr" rid="ref15">15</xref>
        ], etc.
      </p>
      <p>
        However, in contrast to these development, sketching is still a few steps behind the digitisation,
despite its important role as an initial data collection step. Many digitised geological methods
work on visualisation and 3D modelling [
        <xref ref-type="bibr" rid="ref16">16, 17, 18</xref>
        ]. Some research bridge the animated
interaction and drawing with ontologies [19, 20], but these cannot fulfil the needs of geologists
and the industries.
      </p>
      <p>To this end, we propose an ontology-based sketching system to allow users to document
geological structure information formally so that computers can process them. This system
contributes the encoding of first-hand geological structure information from a user-driven
perspective, making the information findable, accessible, interoperable, reusable (FAIR), and
suitable for inference, and meeting the needs of digitised industry. We present our on-going
research on the ontology-based system in this paper, and it is organised as follows.
• A discussion of lack of studies on sketches (Section 2).
• A early phase work of the structural geology ontology (Section 3)
• A preliminary system architecture (Section 3) that consists of three layers: the user sketch
interface layer, the domain ontology layer, and the intermediate mapping layer.
• A preview of the evaluation methods(Section 4)
• A general conclusion with our future work (Section 5)</p>
    </sec>
    <sec id="sec-2">
      <title>2. Related Work</title>
      <p>
        Industrial Impact of Geological Sketches. Geological sketches have long been used in
industry. In the traditional petroleum industry, geologists use sketches to express their understanding
of geological structure in the subsurface seismic to assist hydrocarbon exploration [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ]. In the
mining industry, one basic approach to prevent mining subsidence and failure is to study
regional geological structures, especially preexisting faults [
        <xref ref-type="bibr" rid="ref6">6</xref>
        ]. In the sustainable energy industry,
geothermal or carbon capture and storage require a sound examination of geological fracture
systems to evaluate fluid injection, transport, and storage [
        <xref ref-type="bibr" rid="ref7">7, 21</xref>
        ], In the construction industry,
especially in railway and tunnel construction, preventing landslide and tunnel water leakage,
and reducing construction failure are also based on the study of geological structures [22].
Work on Semantification of Geological Data. Relying on semantic technologies, much
work has been done to support and enhance industrial geological data interoperability, such
as ontological modelling, reasoning, knowledge graph construction etc. Various ontologies
have been proposed, such as the Ontology of Fractures [
        <xref ref-type="bibr" rid="ref11">11</xref>
        ] and the GeoCore Ontology [
        <xref ref-type="bibr" rid="ref12">12</xref>
        ].
Qualitative data-based geological multi-scenario reasoning has been proven its usefulness [
        <xref ref-type="bibr" rid="ref13">13</xref>
        ].
The work [
        <xref ref-type="bibr" rid="ref13">13</xref>
        ] designed an ontology-driven representation of knowledge to support the
machinereadable geological knowledge interoperability. Based on natural language processing and data
mining, a new approach has been developed to construct geological knowledge graphs [
        <xref ref-type="bibr" rid="ref15">15</xref>
        ].
      </p>
      <p>
        Another work [
        <xref ref-type="bibr" rid="ref14">14</xref>
        ] aims at integrating reasoning rules to understand users’ intentions and
problems to improve information retrieval eficiency.
      </p>
      <p>
        Lack of Study on Sketches. Some drawing tools are designed as digitised canvases to assist
2D/3D modelling, drawing, and visualisation [
        <xref ref-type="bibr" rid="ref16">16, 17, 18</xref>
        ], but these visualisation artefacts
themselves contain no geological information, and are not machine-readable. Most information
is still reported as PDF files with forms, tables, and raster images with interpretations. To solve
this problem, ontology-based image annotation tools have been proposed to add meaning to
images [23, 24]. Besides, some ontology-based approaches have been ofered to harmonise
the geological fault detection and geological layer horizon in seismic image interpretation and
integrate with geological time [25, 26]. Wang et al. [27] developed a semi-automated method to
utilise text content and elevation model in old geological paper reports to convert raster images
(e.g.geologic illustrations) into vector profiles at low cost. Ontology-based CAD systems like
FieldLog [28] had been implemented to enable geological database flexibility and balance the
needs between users and industries. Ma et al. [20] built an ontology with animated interactive
functions to improve data interoperability. An ontology-based sketching tool was designed
by Forbus et al. [19] to make sketches, in general, more meaningful, though it was mainly
used for education and cognitive science purpose. Inspired by several approaches with similar
technologies or goals have been published, our work is having one step forward to satisfy the
needs of the geology-relevant industries.
      </p>
    </sec>
    <sec id="sec-3">
      <title>3. Our Sketch-Based System for Industrial Geological</title>
    </sec>
    <sec id="sec-4">
      <title>Information Capture</title>
      <p>We now introduce our system and the methodology.</p>
      <p>System Architecture. Our sketch-based system has a three-layered architecture: the user
sketch interface layer, the domain knowledge ontology layer, and the intermediate mapping
layer (Figure 1). The user sketch interface layer is a front-end layer that users draw and input
their geological information. The domain knowledge ontology layer provides formal structural
geology knowledge. The intermediate mapping layer takes the sketch input from the user
sketch interface layer and links it with formal knowledge from the domain knowledge ontology
layer, and generates the knowledge graph based on the mapping.</p>
      <p>Process of Knowledge Engineering. As a work of developing an ontology-based sketch
system for generating geologic structural information knowledge graphs, constructing a
suitable ontology for the domain knowledge is the first step. The target domain knowledge
is specified in describing the structural geologic scenarios agreed by domain experts. To do
this, we first collect vocabularies that geologists use from structural geology publications. Due
to the large range of the domain, we concentrate our knowledge acquisition work on geologic
structural fault and its relevant concepts as the foundation.</p>
      <p>
        After collecting vocabularies, together with domain experts, a taxonomy has been built to
contain collected vocabularies. Based on domain experts’ reflections, synonyms, conflicts, and
ambiguities were discussed and sorted out during this process. The knowledge is formalised into
a structure that is precise in meaning. In addition to the correctness of the conceptualisation,
the unified terminologies, to a great extent, agreed by domain experts to balance the conciseness
and clarity of our work. To not reinvent the wheel, the work was in alignment with existing
ontologies e.g. Fracture Ontology [
        <xref ref-type="bibr" rid="ref11">11</xref>
        ] and GeoCore Ontology [
        <xref ref-type="bibr" rid="ref12">12</xref>
        ] to build object properties,
data properties, and classes of the tailored ontology. With a unified top-level ontology as the
backbone, this designed ontology will allow modifications to adapt diferent sub-domain usage
of the geology. The schematic illustration of part of the tailored ontology is displayed in Figure 2
with four main classes of entities displayed in a hierarchical view.
      </p>
      <p>Our GeoStructure Ontology. Figure 2 displays the sub-classes of the rock, geological object,
geological process, and geological structure and their relationships in the domain of structural
geologic fault. The geological object is displayed in the central and other three entities by
diferent object properties. The system will generate corresponding knowledge graphs based
on this ontology following users’ sketching processes. A real-world structural geologic fault
system has been used to examine the ontology’s usability, completeness, and expressivity and
the resulting knowledge graph is discussed in Sect. 4 and illustrated in Fig. 3.
User Interface Design and Knowledge Mapping The user interface development is in the
stage of wireframe designing. The challenges include how to bridge the graphic sketch part and
the knowledge based part of the system and make the interface easy for industrial users and
geologists. Using a high-level language to make ontology templates is a potential solution for the
ifrst challenge. Solving the second challenge will require a solid user study and interdisciplinary
discussions.</p>
    </sec>
    <sec id="sec-5">
      <title>4. Evaluation and Industrial Applications</title>
      <p>System Verification. The verification of the ontology is designed in two parts. (1) Competency
Questions. The competency questions are provided by domain experts, and reflect critical
knowledge that needs to be captured in mainly three aspects: fault type, rock layer composition,
and numeric properties. Questions asking for the type of a given fault, the composition of some
layers, and the strike/dip values of the fault, will use to test the ontology. Such questions are
expected to be answered by a knowledge graph adhering to the designed ontology. In addition
to the ontology and knowledge graph verification, future evaluation will use workshops and
interviews as user experience study methods to evaluate the usability of the system, and
what components are required for the system. (2) Examination of Use Cases. In addition to the
competency questions, real scenarios from on-shore field observation and ofshore research
work will be used to examine the ontology’s correctness, completeness, and expressivity and
ensure that it can fully describe the scenarios and approved by domain experts?
Examination: Sketch information capture with semi-automated KG generation. In
the current stage, the generated knowledge graph’s clarity is the main focus. To this aim, we
proposed a real scenario in Fig. 3a to see how the a knowledge graph can describe it. Fig. 3a is a
structural geology scenario with faults and host rocks; Fig. 3b is a simple geological sketch of
the scenario in Fig. 3a; Fig. 3c is an illustration of part of the corresponding knowledge graph.
The knowledge graph describes the fault type, the relationship between faults and host rocks,
the composition of the host rocks, and the core numeric values of this scenario concisely.
Applications High quality information and access eficient are essential for digitised industries.
Over time, semantically annotated sketches will form a searchable library, allowing more
eficient access to information than with traditional text- and image-based publications. The
generated information can also support supervised machine learning and qualitative geological
information reasoning in the future to assist users’ decision making. The applications’ evaluation
will be based on industrial needs to run workshops and demos to evaluate the system.</p>
    </sec>
    <sec id="sec-6">
      <title>5. Conclusion and Outlook</title>
      <p>Conclusion. This paper presents our ongoing research on providing an industrially relevant
information capture method in structural geology. Based on domain experts’ requirements and
existing ontologies, a preliminary ontology has been tailored for the domain to formalise the
knowledge. The capture system generates knowledge graphs in a semi-automated way based
on users’ sketch input. We use a real geological scenario to validate the usage of our knowledge
model and the generated knowledge graph. The generated knowledge graph is retrievable,
reusable, machine-readable, and suitable for inference.</p>
      <p>Outlook. Beyond the current work, the front-end system is under development. Our next goal
is to bridge the front-end graphical system and the back-end knowledge base and demonstrate
the work to more users to evaluate the system’s usefulness. The unified ontology shows
great potential in adopting other disciplines of geology, which leaves the possibility for future
extension.</p>
    </sec>
    <sec id="sec-7">
      <title>Acknowledgments</title>
      <p>This publication is supported by the European Commission H2020 projects Dome 4.0 (Grant
Agreement No. 953163), OntoCommons (Grant Agreement No. 958371), and DataCloud (Grant
Agreement No. 101016835) and the SIRIUS Centre, Norwegian Research Council project number
237898. We gratefully acknowledge the economic support from The Research Council of
Norway and Equinor ASA through Research Council project “308817 - Digital wells for optimal
production and drainage” (DigiWell).
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