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<front>
<journal-meta>
<journal-id journal-id-type="publisher">ISPRS-Archives</journal-id>
<journal-title-group>
<journal-title>The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences</journal-title>
<abbrev-journal-title abbrev-type="publisher">ISPRS-Archives</abbrev-journal-title>
<abbrev-journal-title abbrev-type="nlm-ta">Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci.</abbrev-journal-title>
</journal-title-group>
<issn pub-type="epub">2194-9034</issn>
<publisher><publisher-name>Copernicus Publications</publisher-name>
<publisher-loc>Göttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/isprs-archives-L-4-W2-2026-253-2026</article-id>
<title-group>
<article-title>Extending 3DCityDB with Oracle AI Database Support and LLM-Based Natural Language Interfaces</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Yao</surname>
<given-names>Zhihang</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Patenge</surname>
<given-names>Karin</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Gong</surname>
<given-names>Huiling</given-names>
</name>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Nagel</surname>
<given-names>Claus</given-names>
</name>
<xref ref-type="aff" rid="aff4">
<sup>4</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Kolbe</surname>
<given-names>Thomas H.</given-names>
</name>
<xref ref-type="aff" rid="aff5">
<sup>5</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Centre for Geodesy and Geoinformatics, Stuttgart Technical University of Applied Sciences (HFT Stuttgart), Stuttgart, Germany</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>Oracle Global Services Germany GmbH</addr-line>
</aff>
<aff id="aff3">
<label>3</label>
<addr-line>Oracle Corporation, USA</addr-line>
</aff>
<aff id="aff4">
<label>4</label>
<addr-line>Virtual City Systems, Berlin, Germany</addr-line>
</aff>
<aff id="aff5">
<label>5</label>
<addr-line>Chair of Geoinformatics, Technical University of Munich, Germany</addr-line>
</aff>
<pub-date pub-type="epub">
<day>28</day>
<month>09</month>
<year>2026</year>
</pub-date>
<volume>L-4/W2-2026</volume>
<fpage>253</fpage>
<lpage>259</lpage>
<permissions>
<copyright-statement>Copyright: &#x000a9; 2026 Zhihang Yao et al.</copyright-statement>
<copyright-year>2026</copyright-year>
<license license-type="open-access">
<license-p>This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit <ext-link ext-link-type="uri"  xlink:href="https://creativecommons.org/licenses/by/4.0/">https://creativecommons.org/licenses/by/4.0/</ext-link></license-p>
</license>
</permissions>
<self-uri xlink:href="https://isprs-archives.copernicus.org/articles/L-4-W2-2026/253/2026/isprs-archives-L-4-W2-2026-253-2026.html">This article is available from https://isprs-archives.copernicus.org/articles/L-4-W2-2026/253/2026/isprs-archives-L-4-W2-2026-253-2026.html</self-uri>
<self-uri xlink:href="https://isprs-archives.copernicus.org/articles/L-4-W2-2026/253/2026/isprs-archives-L-4-W2-2026-253-2026.pdf">The full text article is available as a PDF file from https://isprs-archives.copernicus.org/articles/L-4-W2-2026/253/2026/isprs-archives-L-4-W2-2026-253-2026.pdf</self-uri>
<abstract>
<p>The open-source 3D City Database (3DCityDB) is a widely used solution for storing and managing semantic 3D city models based on the CityGML standard. Its latest version 5 introduces a redesigned and highly generic schema along with a JSON-based schema mapping mechanism, which was initially supported only by PostgreSQL with the PostGIS extension. This paper presents the extension of 3DCityDB to the Oracle AI Database, which offers a database-native natural language interface for interacting with the database. Following a model-driven approach, we ported the complete schema from PostgreSQL to Oracle within a unified relational modelling environment. We implemented a lightweight Oracle adapter that shares a common interface with the PostgreSQL version in the citydb-tool to keep import, export, and query workflows consistent across both database platforms. One of the main research challenges arises when integrating LLM-based natural-language-to-SQL (NL2SQL) through the Oracle SELECT AI package. It typically conveys database semantics via static annotations on fixed physical tables and columns, whereas 3DCityDB v5 adopts a generic Entity-Attribute-Value (EAV) schema whose semantics are encapsulated as JSON in metadata tables. As a result, annotations alone cannot express the structure required for correct query generation. To bridge this gap, we propose a schema-driven approach that automatically derives a dedicated database view from the JSON schema mappings and renders it into a compact, LLM-readable context, which is then injected into the SELECT AI prompt. This enables general-purpose LLMs to resolve hierarchical relationships and generate recursive SQL.</p>
</abstract>
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