9 Search Results for "Hahmann, Torsten"

Document
DOI: 10.4230/LIPIcs.GIScience.2025.4
Precomputed Topological Relations for Integrated Geospatial Analysis Across Knowledge Graphs

Authors: Katrina Schweikert, David K. Kedrowski, Shirly Stephen, and Torsten Hahmann

Published in: LIPIcs, Volume 346, 13th International Conference on Geographic Information Science (GIScience 2025)

Abstract
Geospatial Knowledge Graphs (GeoKGs) represent a significant advancement in the integration of AI-driven geographic information, facilitating interoperable and semantically rich geospatial analytics across various domains. This paper explores the use of topologically enriched GeoKGs, built on an explicit representation of S2 Geometry alongside precomputed topological relations, for constructing efficient geospatial analysis workflows within and across knowledge graphs (KGs). Using the SAWGraph knowledge graph as a case study focused on enviromental contamination by PFAS, we demonstrate how this framework supports fundamental GIS operations - such as spatial filtering, proximity analysis, overlay operations and network analysis - in a GeoKG setting while allowing for the easy linking of these operations with one another and with semantic filters. This enables the efficient execution of complex geospatial analyses as semantically-explicit queries and enhances the usability of geospatial data across graphs. Additionally, the framework eliminates the need for explicit support for GeoSPARQL’s topological operations in the utilized graph databases and better integrates spatial knowledge into the overall semantic inference process supported by RDFS and OWL ontologies.
Cite as

Katrina Schweikert, David K. Kedrowski, Shirly Stephen, and Torsten Hahmann. Precomputed Topological Relations for Integrated Geospatial Analysis Across Knowledge Graphs. In 13th International Conference on Geographic Information Science (GIScience 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 346, pp. 4:1-4:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{schweikert_et_al:LIPIcs.GIScience.2025.4,
  author =	{Schweikert, Katrina and Kedrowski, David K. and Stephen, Shirly and Hahmann, Torsten},
  title =	{{Precomputed Topological Relations for Integrated Geospatial Analysis Across Knowledge Graphs}},
  booktitle =	{13th International Conference on Geographic Information Science (GIScience 2025)},
  pages =	{4:1--4:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-378-2},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{346},
  editor =	{Sila-Nowicka, Katarzyna and Moore, Antoni and O'Sullivan, David and Adams, Benjamin and Gahegan, Mark},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.GIScience.2025.4},
  URN =		{urn:nbn:de:0030-drops-238332},
  doi =		{10.4230/LIPIcs.GIScience.2025.4},
  annote =	{Keywords: knowledge graph, GeoKG, spatial analysis, ontology, SPARQL, GeoSPARQL, discrete global grid system, S2 geometry, GeoAI, PFAS}
}
Artifact
Software
DOI: 10.4230/artifacts.24220
SAWGraph Example Geospatial SPARQL Queries

Authors: Katrina Schweikert, David Kedrowski, Shirly Stephen, and Torsten Hahmann

Abstract
Cite as

Katrina Schweikert, David Kedrowski, Shirly Stephen, Torsten Hahmann. SAWGraph Example Geospatial SPARQL Queries (Software, SPARQL queries). Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@misc{dagstuhl-artifact-24220,
   title = {{SAWGraph Example Geospatial SPARQL Queries}}, 
   author = {Schweikert, Katrina and Kedrowski, David and Stephen, Shirly and Hahmann, Torsten},
   note = {Software, version 1.1., NSF Grant 2333782: "Safe Agricultural Products and Water Graph (SAWGraph): An OKN to Monitor and Trace PFAS and Other Contaminants in the Nation’s Food and Water Systems", UMaine Center of Excellence associated with USDA-ARS New England Center for Sustained Soil and Water Health, swhId: \href{https://archive.softwareheritage.org/swh:1:dir:678ee78feb48f235c42bd5722e4c19f81f91f9dc;origin=https://github.com/SAWGraph/public;visit=swh:1:snp:62ba983ad514540fecdcecfc2ea8f3d13e723b5f;anchor=swh:1:rev:2356e76e79be326bf6a6c024a78a6dae95b936d9}{\texttt{swh:1:dir:678ee78feb48f235c42bd5722e4c19f81f91f9dc}} (visited on 2025-08-15)},
   url = {https://github.com/SAWGraph/public/tree/main/UseCases/UC3-Tracing/UC3-CQ15/GIScience2025-queries},
   doi = {10.4230/artifacts.24220},
}
Document
Research
DOI: 10.4230/TGDK.3.1.4
CoaKG: A Contextualized Knowledge Graph Approach for Exploratory Search and Decision Making

Authors: Veronica dos Santos, Daniel Schwabe, Altigran Soares da Silva, and Sérgio Lifschitz

Published in: TGDK, Volume 3, Issue 1 (2025). Transactions on Graph Data and Knowledge, Volume 3, Issue 1

Abstract
In decision-making scenarios, an information need arises due to a knowledge gap when a decision-maker needs more knowledge to make a decision. Users may take the initiative to acquire knowledge to fill this gap through exploratory search approaches using Knowledge Graphs (KGs) as information sources, but their queries can be incomplete, inaccurate, and ambiguous. Although KGs have great potential for exploratory search, they are incomplete by nature. Besides, for both Crowd-sourced KGs and KGs constructed by integrating several different information sources of varying quality to be effectively consumed, there is a need for a Trust Layer. Our research aims to enrich and allow querying KGs to support context-aware exploration in decision-making scenarios. We propose a layered architecture for Context Augmented Knowledge Graphs-based Decision Support Systems with a Knowledge Layer that operates under a Dual Open World Assumption (DOWA). Under DOWA, the evaluation of the truthfulness of the information obtained from KGs depends on the context of its claims and the tasks carried out or intended (purpose). The Knowledge Layer comprises a Context Augmented KG (CoaKG) and a CoaKG Query Engine. The CoaKG contains contextual mappings to identify explicit context and rules to infer implicit context. The CoaKG Query Engine is designed as a query-answering approach that retrieves all contextualized answers from the CoaKG. A Proof of Concept (PoC) based on Wikidata was developed to evaluate the effectiveness of the Knowledge Layer.
Cite as

Veronica dos Santos, Daniel Schwabe, Altigran Soares da Silva, and Sérgio Lifschitz. CoaKG: A Contextualized Knowledge Graph Approach for Exploratory Search and Decision Making. In Transactions on Graph Data and Knowledge (TGDK), Volume 3, Issue 1, pp. 4:1-4:27, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@Article{dossantos_et_al:TGDK.3.1.4,
  author =	{dos Santos, Veronica and Schwabe, Daniel and da Silva, Altigran Soares and Lifschitz, S\'{e}rgio},
  title =	{{CoaKG: A Contextualized Knowledge Graph Approach for Exploratory Search and Decision Making}},
  journal =	{Transactions on Graph Data and Knowledge},
  pages =	{4:1--4:27},
  ISSN =	{2942-7517},
  year =	{2025},
  volume =	{3},
  number =	{1},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/TGDK.3.1.4},
  URN =		{urn:nbn:de:0030-drops-236685},
  doi =		{10.4230/TGDK.3.1.4},
  annote =	{Keywords: Knowledge Graphs, Context Search, Decision Support}
}
Document
Resource Paper
DOI: 10.4230/TGDK.2.2.5
The Reasonable Ontology Templates Framework

Authors: Martin Georg Skjæveland and Leif Harald Karlsen

Published in: TGDK, Volume 2, Issue 2 (2024): Special Issue on Resources for Graph Data and Knowledge. Transactions on Graph Data and Knowledge, Volume 2, Issue 2

Abstract
Reasonable Ontology Templates (OTTR) is a templating language for representing and instantiating patterns. It is based on simple and generic, but powerful, mechanisms such as recursive macro expansion, term substitution and type systems, and is designed particularly for building and maintaining RDF knowledge graphs and OWL ontologies. In this resource paper, we present the formal specifications that define the OTTR framework. This includes the fundamentals of the OTTR language and the adaptions to make it fit with standard semantic web languages, and two serialization formats developed for semantic web practitioners. We also present the OTTR framework’s support for documenting, publishing and managing template libraries, and for tools for practical bulk instantiation of templates from tabular data and queryable data sources. The functionality of the OTTR framework is available for use through Lutra, an open-source reference implementation, and other independent implementations. We report on the use and impact of OTTR by presenting selected industrial use cases. Finally, we reflect on some design considerations of the language and framework and present ideas for future work.
Cite as

Martin Georg Skjæveland and Leif Harald Karlsen. The Reasonable Ontology Templates Framework. In Special Issue on Resources for Graph Data and Knowledge. Transactions on Graph Data and Knowledge (TGDK), Volume 2, Issue 2, pp. 5:1-5:54, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@Article{skjaeveland_et_al:TGDK.2.2.5,
  author =	{Skj{\ae}veland, Martin Georg and Karlsen, Leif Harald},
  title =	{{The Reasonable Ontology Templates Framework}},
  journal =	{Transactions on Graph Data and Knowledge},
  pages =	{5:1--5:54},
  ISSN =	{2942-7517},
  year =	{2024},
  volume =	{2},
  number =	{2},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/TGDK.2.2.5},
  URN =		{urn:nbn:de:0030-drops-225896},
  doi =		{10.4230/TGDK.2.2.5},
  annote =	{Keywords: Ontology engineering, Ontology design patterns, Template mechanism, Macros}
}
Artifact
Software
DOI: 10.4230/artifacts.22447
OWL Ontologies for the Urban Flooding Open Knowledge Network (UF-OKN)

Authors: Torsten Hahmann and David K. Kedrowski

Abstract
Cite as

Torsten Hahmann, David K. Kedrowski. OWL Ontologies for the Urban Flooding Open Knowledge Network (UF-OKN) (Software). Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@misc{dagstuhl-artifact-22447,
   title = {{OWL Ontologies for the Urban Flooding Open Knowledge Network (UF-OKN)}}, 
   author = {Hahmann, Torsten and Kedrowski, David K.},
   note = {Software, version 2.1., National Science Foundation, award# 2033607, National Science Foundation, award# 1937099, swhId: \href{https://archive.softwareheritage.org/swh:1:dir:00a0f1fbcd022a6beed4d88b6430567ef1314872;origin=https://github.com/UFOKN/Knowledge-Graph;visit=swh:1:snp:c72cfbb7d2958ec9082a9266afc9de82b375f737;anchor=swh:1:rev:4b80c683fa9b83d85e3cb09cadc608069172e308}{\texttt{swh:1:dir:00a0f1fbcd022a6beed4d88b6430567ef1314872}} (visited on 2024-11-28)},
   url = {https://github.com/UFOKN/Knowledge-Graph/tree/master/ontologies/v2.1},
   doi = {10.4230/artifacts.22447},
}
Document
Short Paper
DOI: 10.4230/LIPIcs.COSIT.2024.21
An Ontology and Geospatial Knowledge Graph for Reasoning About Cascading Failures (Short Paper)

Authors: Torsten Hahmann and David K. Kedrowski

Published in: LIPIcs, Volume 315, 16th International Conference on Spatial Information Theory (COSIT 2024)

Abstract
During a natural disaster such as flooding, the failure of a single asset in the complex and interconnected web of critical urban infrastructure can trigger a cascade of failures within and across multiple systems with potentially life-threatening consequences. To help emergency management effectively and efficiently assess such failures, we design the Utility Connection Ontology Design Pattern to represent utility services and model connections within and across those services. The pattern is encoded as an OWL ontology and instantiated with utility data in a geospatial knowledge graph. We demonstrate how it facilitates reasoning to identify cascading service failures due to flooding for producing maps and other summaries for situational awareness.
Cite as

Torsten Hahmann and David K. Kedrowski. An Ontology and Geospatial Knowledge Graph for Reasoning About Cascading Failures (Short Paper). In 16th International Conference on Spatial Information Theory (COSIT 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 315, pp. 21:1-21:9, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{hahmann_et_al:LIPIcs.COSIT.2024.21,
  author =	{Hahmann, Torsten and Kedrowski, David K.},
  title =	{{An Ontology and Geospatial Knowledge Graph for Reasoning About Cascading Failures}},
  booktitle =	{16th International Conference on Spatial Information Theory (COSIT 2024)},
  pages =	{21:1--21:9},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-330-0},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{315},
  editor =	{Adams, Benjamin and Griffin, Amy L. and Scheider, Simon and McKenzie, Grant},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.COSIT.2024.21},
  URN =		{urn:nbn:de:0030-drops-208364},
  doi =		{10.4230/LIPIcs.COSIT.2024.21},
  annote =	{Keywords: knowledge graph, ontology, OWL, spatial reasoning, cascading failures, urban infrastructure}
}
Document
DOI: 10.4230/LIPIcs.COSIT.2019.15
Formal Qualitative Spatial Augmentation of the Simple Feature Access Model

Authors: Shirly Stephen and Torsten Hahmann

Published in: LIPIcs, Volume 142, 14th International Conference on Spatial Information Theory (COSIT 2019)

Abstract
The need to share and integrate heterogeneous geospatial data has resulted in the development of geospatial data standards such as the OGC/ISO standard Simple Feature Access (SFA), that standardize operations and simple topological and mereotopological relations over various geometric features such as points, line segments, polylines, polygons, and polyhedral surfaces. While SFA’s supplied relations enable qualitative querying over the geometric features, the relations' semantics are not formalized. This lack of formalization prevents further automated reasoning - apart from simple querying - with the geometric data, either in isolation or in conjunction with external purely qualitative information as one might extract from textual sources, such as social media. To enable joint qualitative reasoning over geometric and qualitative spatial information, this work formalizes the semantics of SFA’s geometric features and mereotopological relations by defining or restricting them in terms of the spatial entity types and relations provided by CODIB, a first-order logical theory from an existing logical formalization of multidimensional qualitative space.
Cite as

Shirly Stephen and Torsten Hahmann. Formal Qualitative Spatial Augmentation of the Simple Feature Access Model. In 14th International Conference on Spatial Information Theory (COSIT 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 142, pp. 15:1-15:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)

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@InProceedings{stephen_et_al:LIPIcs.COSIT.2019.15,
  author =	{Stephen, Shirly and Hahmann, Torsten},
  title =	{{Formal Qualitative Spatial Augmentation of the Simple Feature Access Model}},
  booktitle =	{14th International Conference on Spatial Information Theory (COSIT 2019)},
  pages =	{15:1--15:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-115-3},
  ISSN =	{1868-8969},
  year =	{2019},
  volume =	{142},
  editor =	{Timpf, Sabine and Schlieder, Christoph and Kattenbeck, Markus and Ludwig, Bernd and Stewart, Kathleen},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.COSIT.2019.15},
  URN =		{urn:nbn:de:0030-drops-111074},
  doi =		{10.4230/LIPIcs.COSIT.2019.15},
  annote =	{Keywords: space, geometry, geospatial semantics, qualitative spatial representation (QSR), simple feature access, topological relations, formal ontology}
}
Document
Short Paper
DOI: 10.4230/LIPIcs.GISCIENCE.2018.59
The Landform Reference Ontology (LFRO): A Foundation for Exploring Linguistic and Geospatial Conceptualization of Landforms (Short Paper)

Authors: Gaurav Sinha, Samantha T. Arundel, Torsten Hahmann, E. Lynn Usery, Kathleen Stewart, and David M. Mark

Published in: LIPIcs, Volume 114, 10th International Conference on Geographic Information Science (GIScience 2018)

Abstract
The landform reference ontology (LFRO) formalizes ontological distinctions underlying naïve geographic cognition and reasoning about landforms. The LFRO taxonomy is currently based only on form-based distinctions. In this significantly revised version, several new categories have been added to explicate ontological distinctions related to material-spatial dependence and physical support. Nuances of common natural language landform terms and implications for their mapping are discussed.
Cite as

Gaurav Sinha, Samantha T. Arundel, Torsten Hahmann, E. Lynn Usery, Kathleen Stewart, and David M. Mark. The Landform Reference Ontology (LFRO): A Foundation for Exploring Linguistic and Geospatial Conceptualization of Landforms (Short Paper). In 10th International Conference on Geographic Information Science (GIScience 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 114, pp. 59:1-59:7, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{sinha_et_al:LIPIcs.GISCIENCE.2018.59,
  author =	{Sinha, Gaurav and Arundel, Samantha T. and Hahmann, Torsten and Usery, E. Lynn and Stewart, Kathleen and Mark, David M.},
  title =	{{The Landform Reference Ontology (LFRO): A Foundation for Exploring Linguistic and Geospatial Conceptualization of Landforms}},
  booktitle =	{10th International Conference on Geographic Information Science (GIScience 2018)},
  pages =	{59:1--59:7},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-083-5},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{114},
  editor =	{Winter, Stephan and Griffin, Amy and Sester, Monika},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.GISCIENCE.2018.59},
  URN =		{urn:nbn:de:0030-drops-93873},
  doi =		{10.4230/LIPIcs.GISCIENCE.2018.59},
  annote =	{Keywords: landform, reference ontology, terrain reasoning, dependence, support}
}
Document
DOI: 10.4230/LIPIcs.COSIT.2017.7
An Ontological Framework for Characterizing Hydrological Flow Processes

Authors: Shirly Stephen and Torsten Hahmann

Published in: LIPIcs, Volume 86, 13th International Conference on Spatial Information Theory (COSIT 2017)

Abstract
The spatio-temporal processes that describe hydrologic flow - the movement of water above and below the surface of the Earth -- are currently underrepresented in formal semantic representations of the water domain. This paper analyses basic flow processes in the hydrology domain and systematically studies the hydrogeological entities, such as different rock and water bodies, the ground surface or subsurface zones, that participate in them. It identifies the source and goal entities and the transported water (the theme) as common participants in hydrologic flow and constructs a taxonomy of different flow patterns based on differences in source and goal participants. The taxonomy and related concepts are axiomatized in first-order logic as refinements of DOLCE's participation relation and reusing hydrogeological concepts from the Hydro Foundational Ontology (HyFO). The formalization further enhances HyFO and contributes to improved knowledge integration in the hydrology domain.
Cite as

Shirly Stephen and Torsten Hahmann. An Ontological Framework for Characterizing Hydrological Flow Processes. In 13th International Conference on Spatial Information Theory (COSIT 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 86, pp. 7:1-7:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)

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@InProceedings{stephen_et_al:LIPIcs.COSIT.2017.7,
  author =	{Stephen, Shirly and Hahmann, Torsten},
  title =	{{An Ontological Framework for Characterizing Hydrological Flow Processes}},
  booktitle =	{13th International Conference on Spatial Information Theory (COSIT 2017)},
  pages =	{7:1--7:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-043-9},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{86},
  editor =	{Clementini, Eliseo and Donnelly, Maureen and Yuan, May and Kray, Christian and Fogliaroni, Paolo and Ballatore, Andrea},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.COSIT.2017.7},
  URN =		{urn:nbn:de:0030-drops-77639},
  doi =		{10.4230/LIPIcs.COSIT.2017.7},
  annote =	{Keywords: hydrology, flow processes, formal ontology, participation, semantic roles}
}
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