Torsten Hahmann

• PhD
• Professor (Associate) at University of Maine

Contours maps (such as topographic maps) compress the information of a function over a two-dimensional area into a discrete set of closed lines that connect points of equal value (isolines), striking a fine balance between expressiveness and cognitive simplicity. They allow humans to perform many common sense reasoning tasks about the underlying fu...

Comprehensive water data management requires semantically integrating various data models and ontologies that represent hydrologic knowledge. But integration is hampered by nuances in the use of water-related vocabulary (e.g. terms such as water body, aquifer, reservoir, well, etc.) across water representations and by the reliance on a mix of forma...

Water features such as rivers, clouds, and aquifers are primarily understood from sensor measurements. Ontologiesfor the hydro domain play a key role in describing sensor measurements, particularly to aid water data interoperability, but waterfeatures are under-represented in such ontologies. In this paper we build upon existing work in hydro ontol...

While OWL and RDF are by far the most popular logic-based languages for Semantic Web Ontologies, some well-designed ontologies are only available in languages with a much richer expressivity, such as first-order logic (FOL) or the ISO standard Common Logic. This inhibits reuse of these ontologies by the wider Semantic Web Community. While convertin...

A significant portion of scientific knowledge resides within scholarly publications, both in print and digital formats. Recent advancements in natural language processing and information extraction techniques have enhanced the accessibility of this knowledge for further automated querying and processing. Structured and semantically-aware representa...

This paper proposes a framework for representing and reasoning causality between geographic events by introducing the notion of Geo-Situation. This concept links to observational snapshots that represent sets of conditions, and either acts as the setting of a geo-event or influences the initiation of a geo-event. We envision the use of this framewo...

Use and reuse of an ontology requires prior ontology verification which encompasses, at least, proving that the ontology is internally consistent and consistent with representative datasets. First-order logic (FOL) model finders are among the only available tools to aid us in this undertaking, but proving consistency of FOL ontologies is theoretica...

Context and motivation] Legal provisions create a distinct set of requirements for businesses to be compliant with. Capturing legal requirements and managing regulatory compliance is a challenging task in system development. [Question/problem] Part of this task involves modeling legal requirements, which is not trivial for requirements engineers as...

[Context and motivation] Legal provisions create a distinct set of requirements for businesses to be compliant with. Capturing legal requirements and managing regulatory compliance is a challenging task in system development. [Question/problem] Part of this task involves modeling legal requirements, which is not trivial for requirements engineers a...

This article responds to the widespread and oft-noted challenges digital humanists face in working with data that is uncertain and characterised by complex narratives. Using an example drawn from the vast archives of post-war interviews with Holocaust survivors, it draws on approaches developed in Qualitative Spatial Representation (QSR) to explore...

Satisfiability of first-order logic (FOL) ontologies is typically verified by translation to propositional satisfiability (SAT) problems, which is then tackled by a SAT solver. Unfortunately, SAT solvers often experience scalability issues when reasoning with FOL ontologies and even moderately sized datasets. While SAT solvers have been found to ca...

First-order logic, sat solving, propositional satisfiability, ontologies

Geographic information systems (GIS) customarily encode spatial information using geometric objects (points, polylines and polygons) and their locations. But people frequently use qualitative relations, such as topological relations (e.g., connection or overlap) or cardinal direction relations (e.g. North or Southeast), to describe spatial scenes....

This reference landform ontology is intended to guide automated delineation of landforms from digital elevation models (DEMs) and semantic information retrieval about landforms. Since only form related information is available from DEMs, the categories of this reference ontology are defined based only on morphological criteria. The choice of the la...

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...

With ubiquitous live sensors and sensor networks, increasingly large numbers of individual sensors are deployed in physical space. Sensor data streams are a fundamentally novel mechanism to create and deliver observations to information systems, enabling us to represent spatio-temporal continuous phenomena such as radiation accidents, pollen distri...

In this work we discuss an ontology design pattern for mate- rial transformations. It models the relation between products, resources, and catalysts in the transformation process. Our axiomatization goes beyond a mere surface semantics. While we focus on the construction domain, the pattern can also be applied to chemistry and other domains.

Ontology design patterns (ODPs) are widely accepted as important tools for accelerated design of ontologies. We revisit content patterns (CP), an important class of ODPs, and distinguish two kinds based on their degree of formalization and maturity: conceptual CPs and formalized CPs. We show how formalized CPs and the closely related knowledge patt...

We outline ongoing work for constructing higher-level ontological descriptions of the spatial properties of the surfaces of rigid organic objects. Beginning from the adjacency graph generated using an organic shape descriptor, which uses curvature to describe the named surface regions of a bone and the boundary transitions between neighbouring regi...

This paper explores an alternative vision for upper ontologies which is more effective at facilitating the sharability and reusability of ontologies. The notion of generic ontologies is characterized through the formalization of ontological commitments and choices. Ontology repositories are used to modularize ontologies so that any particular upper...

The relation between an object and its matter is fundamental to all physical sciences, and represented widely and diversely in scientific ontologies. An under-appreciated aspect of this relation is the emergence of voids at finer levels of physical granularity. In this paper we enhance the constitution relation to account for the presence of finer...

Material-spatial interdependence (mat-dep) is a type of dependence in which the physical extents of two entities are necessarily and mutually contingent, e.g. an object and its matter, or a hole and its host. Such dependence is commonly found amongst arrangements of physical entities, particularly in models of the natural environment. In this paper...

Full physical containment is the relation in which one physical entity is completely inside another. It is central to the description of natural resources held in reservoirs above or below the surface. Previous ontological representations of containment are located in abstract space, incomplete, or insufficiently incorporate voids, so in this paper...

Through contact algebras we study theories of mereotopology in a uniform way that clearly separates mereological from topological concepts. We identify and axiomatize an important subclass of closure mereotopologies (CMT) called unique closure mereotopologies (UCMTs) whose models always have orthocomplemented contact algebras (OCAs), an algebraic c...

We extend our multidimensional qualitative theory of space based on relative dimension and containment by closures under intersections and differences and by a new primitive relation of boundary containment, a special kind of incidence. We provide a descriptions of the intended structures which ensure that boundary and interior are always clearly d...

The mereotopology RT − has in Stonian p-ortholattices its algebraic counterpart. We study representability of these lattices and show that not all Stonian p-ortholattices can be represented by the set of regular sets of a topological space. We identify five conditions that hold in algebras of regular sets and which can be used to eliminate non-rep...

The very nature of topology and its close relation to how humans perceive space and time make mereotopology an indispensable part of any comprehensive framework for qualitative spatial and temporal reasoning (QSTR). Within QSTR, it has by far the longest history, dating back to descriptions of phenomenological processes in nature (Husserl, 1913; Wh...

From its inception, the focus of ontological engineering has been to support the reusability and shareability of ontologies, as well as interoperability of ontology- based software systems. Among the approaches employed to address these chal- lenges have been ontology repositories and the modularization of ontologies. In this paper we combine these...

Voids are extremely important to water science, because their size and connectivity determines the storage and flow of water both above and below the ground surface. While previous formal theories about voids strictly consider holes hosted inside objects, we generalize voids to also include spaces between objects, and distinguish voids in macroscop...

This chapter focuses on the topological and mereological relations, contact, and parthood, between spatio-temporal regions as axiomatized in so-called mereotopologies. Despite, or because of, their simplicity, a variety of different first-order axiomatizations have been proposed. This chapter discusses their underlying ontological choices and diffe...

Qualitative reasoning about commonsense space often involves entities of different dimensions. We present a weak axiomatization of multidimensional qualitative space based on 'relative dimension' and dimension-independent 'containment' which suffice to define basic dimension-dependent mereotopological relations. We show the relationships to other m...

We present an ontology consisting of a theory of spatial dimension and a theory of dimension-independent mereological and topological relations in space. Though both are fairly weak axiomatizations, their interplay suffices to define various mereotopological relations and to make any necessary dimension constraints explicit. We show that models of...

Within knowledge representation, ontologies are logical theories that support software integration and decision support systems. Ontology verification is concerned with the relationship between the intended structures for an ontology and the models of the axiomatization of the ontology. To verify a particular ontology, we ideally characterize all t...

In this paper we show how the relationships between first-order ontologies within a repository can be used to support ontology verification. We discuss the use of representation theorems and classification theorems to characterize the models of an ontology, and then show how such results can be obtained from notions such as relative interpretation.

Boolean Contact Algebras (BCA) establish the algebraic counterpart of the mereotopolopy induced by the Region Connection Calculus (RCC). Similarly, Stonian p-ortholattices serve as a lattice theoretic version of the ontology RT − of Asher and Vieu. In this paper we study the relationship between BCAs and Stonian p-ortholattices. We show that the sk...

This paper gives an algebraic representation of the subtheories RT-, RT-EC, and RT of Asher and Vieu's first-order ontology of mereotopology RT0. It corrects and extends previous work on the representation of these mereotopologies. We develop the theory of p-ortholattices – lattices that are both orthocomplemented and pseudocomplemented – and show...

Theoretical work on Qualitative Spatial Reasoning (QSR) is abundant, but the actual requirements of practical applications have been widely ignored. This paper discusses how ontolo- gies allow to compare different QSR formalisms with respect to definability of spatial concepts, which are taken from a real- world problem. We introduce the problem of...

We characterize the models of Asher and Vieu's first-order mereotopology RT 0 in terms of mathematical structures with well-defined properties: topological spaces, lattices, and graphs. We give a full representation theorem for the models of the subtheory RT -(RT 0 without existential axioms) as p-ortholattices (pseudocomplemented, orthocomplemente...

Allgemeine Geschäftsprozesse in Hotel-Reservierungs-Systemen werden vorgestellt und mit BPMN modelliert. Einzelne Modellierungsaspekte bei der Erstellung der BPMN-Prozessmodelle für ehotel.de offenbaren Stärken und Schwächen der Notation. Ein Ansatz zur Darstellung von Laufzeitvarianten in den Prozessphasen wird entwickelt.

Industry has adopted service orientation paradigm over the last years. Automatic service discovery, dynamic service composition and process adaptability will bring SOA to its full potential. The integrated research project "Adaptive Services Grid" realizes a platform providing such automation functionalities based on semantics. Enhancing SOA with s...