<p>The European Plate Observing System (EPOS, www.epos-ip.org) is a multidisciplinary pan-European research infrastructure for solid Earth science. It integrates a series of domain-specific service hubs such as the Geological Information and Modelling Technical Core Service (TCS GIM) dedicated to access data, data products and services on European boreholes, geological and geohazards maps, mineral resources as well as a catalogue of 3D models. These are hosted by European Geological Surveys and national research organisations.</p><p>Even though interoperability implementation frameworks are well described and used (ISO, OGC, IUGS/CGI, INSPIRE …), it proved to be difficult for several data providers to deploy in the first place the required OGC services supporting the full semantic definition (OGC Complex Feature) to discover and view millions of geological entities. Instead, data are collected and exposed using a simpler yet standardised description (GeoSciML Lite & EarthResourceML Lite). Subsequently, the more complex data flows are deployed with the corresponding semantics.</p><p>This approach was applied to design and implement the European Borehole Index and associated web services (View-WMS and Discovery-WFS) and extended to 3D Models. TCS GIM exposes to EPOS Central Integrated Core Services infrastructure a metadata catalogue service, a series of “index services”, a codeList registry and a Linked Data resolver. These allow EPOS end users to search and locate boreholes, geological maps and features, 3D models, etc., based on the information held by the index services.</p><p>In addition to these services, TCS GIM focussed particularly on sharing European geological data using the Linked Data approach. Each instance is associated with a URI and points to other information resources also using URIs. The Linked Data principles ensure the best semantic description (e.g. URIs to shared codeList registries entries) and also enrich an initial “information seed” (e.g. a set of Borehole entries matching a search) with more contents (e.g. URIs to more Features or a more complex description). As a result, this pattern including Simple Feature and Linked Data has a positive effect on the IT architecture: interoperable services are simpler and faster to deploy and there is no need to harvest a full OGC Complex Feature dataset. This architecture is also more scalable and sustainable.</p><p>The European Geological Services codeList registries have been enriched with new vocabularies as part of the European Geoscience Registry. In compliance with the relevant European INSPIRE rules, this registry is now part of the INPIRE Register Federation, the central access point to the repository for vocabulary and resources. European Geoscience Registry is available for reuse and extension by other geoscientific projects.</p><p>During the EPOS project, this approach has been developed and implemented for the Borehole and Model data services. TCS GIM team provided feedback on INSPIRE through the Earth Science Cluster, contributed to the creation of the OGC GeoScience Domain Working Group in 2017, the launch of the OGC Borehole Interoperability Experiment in 2018, and proposed evolutions to the OGC GeoSciML and IUGS/CGI EarthResourceML standards.</p>

<p>This study presents an approach on how to establish Conceptual Interoperability for autonomous, multidisciplinary systems participating in Research Infrastructures, Early Warning, or Risk Management Systems. Although promising implementations already exist, true interoperability is far from being achieved. Therefore, reference architectures and principles of Systems-of-Systems are adapted for a fully specified, yet implementation-independent Conceptual Model, establishing interoperability to the highest possible degree. The approach utilises use cases and requirements from geological information processing and modelling within the European Plate Observing System (EPOS).</p><p>Conceptual Interoperability can be accomplished by enabling Service Composability. Unlike integration, composability allows interactive data processing and beyond, evolving systems that enable interpretation and evaluation by any potential participant. Integrating data from different domains often leads to monolithic services that are implemented only for a specific purpose (Stovepipe System). Consequently, composability is essential for collaborative information processing, especially in modern interactive computing and exploration environments. A major design principle for achieving composability is Dependency Injection, allowing flexible combinations (Loose Coupling) of services that implement common, standardised interfaces (abstractions). Another decisive factor for establishing interoperability are Metamodels of data models that specify data and semantics regardless of their domain, based on a common, reusable approach. Thus, data from different domains can be represented by one common encoding that e.g. abstracts landslides (geophysical models) or buildings (urban planning) based on their geometry. An indispensable part of a Conceptual Model is detailed semantics, which not only requires terms from Domain-Controlled Vocabularies, but also ontologies providing qualified statements about the relationship between data and associated concepts. This is of major importance for evolutionary systems that are able to comprehend and react to state changes. Maximum interoperability also requires strict modularisation for a clear separation of semantics, metadata and the data itself.</p><p>Conceptual models for geological information that are governed by the described principles and their implementations are still far away. Moreover, a route to achieve such models is not straightforward. They span a multitude of communities and are far too complex for conventional implementation in project form. A first step could be applying modern design principles to new developments in the various scientific communities and join the results under a common stewardship like the Open Geospatial Consortium (OGC). Recently, a Metamodel has been developed within the OGC’s Borehole Interoperability Experiment (BoreholeIE); initiated and led by the French Geological Survey (BRGM). It combines the ISO standard (19148:2012 linear referencing) for localisation along borehole paths with the adaption of different encodings of borehole logs based on well-established OGC standards. Further developments aim at correlating borehole logs, geological or geotechnical surveys, and geoscientific models. Since results of surveys are often only available as non-schematised interpretations in text form, interoperability requires formal classifications, which can be derived from machine learning methods applied to the interpretations. As part of a Conceptual Model, such classifications can be used for an automated exchange of standard-conform borehole logs or to support the generation of expert opinions on soil investigations.</p>

The European Plate Observing System (EPOS, www.epos-eu.org) is a multidisciplinary pan-European research infrastructure for solid Earth science. It integrates a series of domain-specific service hubs (Thematic Core Service, TCS) such as the Geological Information and Modelling, which provides access to data, data products and services on European boreholes, geological maps, mineral occurrences, mines and 3D models. TCS GIM services are hosted by a group of European Geological Surveys and a couple of national research organizations. This paper presents novel data discovery and integration, facilitated using borehole logging information with on-demand web services to produce 3D geological structures. This domain interoperability across EPOS was created for the purpose of research, but it is also highly relevant for the response to societal grand challenges such as natural hazards and climate change. European and international interoperability implementation frameworks are well described and used (e.g., INSPIRE, ISO, OGC, and IUGS/CGI). It can be difficult for data providers to deploy web services that support the full semantic data definition (e.g., OGC Complex Feature) to expose several millions of geological entities through web-enabled data portals as required by pan-European projects. The TCS GIM group implemented and innovatively extended two standardized descriptions, i.e. GeoSciML-Lite and EarthResourceML-Lite, with an important reuse of content from Linked Data Registries. This approach was applied to design and implement the European Borehole Index and associated web services (View-WMS and Discovery-WFS), extended to 3D models, geological maps as well as mineral occurrences and mines. Results presented here apply the Linked Data approach ensuring optimal semantic description and enriching the data graphs, with complex descriptions and contents. In this way, it is now possible to traverse from one Borehole Index instance to linked richer information such as the borehole geological log, groundwater levels, rock sample description, analyses, etc. All this detailed information is served following international interoperability standards (Observations & Measurements, GroundWaterML 2.0, GeoSciML4, amongst others).