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Documents authored by Stephen, Shirly

Artifact
Software
DOI: 10.4230/artifacts.24220
SAWGraph Example Geospatial SPARQL Queries

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

Abstract
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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
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.
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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}
}
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.
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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
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.
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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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