Uli Sattler

The University of Manchester · School of Computer Science

This article provides an introduction to the Festschrift that has been put together on the occasion of Franz Baader’s 60th birthday to celebrate his fundamental and highly influential scientific contributions. We start with a brief and personal overview of Franz’s career, listing some important collaborators, places, and scientific milestones, and...

We extend description logics (DLs) with non-monotonic reasoning features. We start by investigating a notion of defeasible subsumption in the spirit of defeasible conditionals as studied by Kraus, Lehmann and Magidor in the propositional case. In particular, we consider a natural and intuitive semantics for defeasible subsumption, and investigate K...

Designing good multiple choice questions (MCQs) for education and assessment is time consuming and error-prone. An abundance of structured and semi-structured data has led to the development of automatic MCQ generation methods. Recently, ontologies have emerged as powerful tools to enable the automatic generation of MCQs. However, current question...

SNOMED International is working on a query language specification for SNOMED CT, which we call here SCTQL. SNOMED CT is the leading terminology for use in Electronic Health Records (EHRs). SCTQL can contribute to effective retrieval and reuse of clinical information within EHRs. This paper analyses the functional capabilities needed for SCTQL and p...

Automated acquisition (learning) of ontologies from data has attracted research interest because it can complement manual, expensive construction of ontologies. We investigate the problem of General Terminology Induction in OWL, i.e. acquiring general, expressive TBox axioms (hypotheses) from an ABox (data). We define novel measures designed to rig...

Reasoning with SROIQ ( D ) , the logic that underpins the popular Web Ontology Language (OWL), has a high worst case complexity (N2Exptime). Decomposing the ontology into modules prior to classification, and then classifying the composites one-by-one, has been suggested as a way to mitigate this complexity in practice. Modular reasoning is curre...

In order to provide support for the construction of MCQs, there have been recent efforts to generate MCQs with controlled difficulty from OWL ontologies. Preliminary evaluation suggests that automatically generated questions are not field ready yet and highlight the need for further evaluations. In this study, we have presented an extensive evaluat...

With the growing interest in using ontologies in semantically-enabled applications, the interest in enhancing the quality of such ontologies has grown as well. Standard reasoning services focus on certain obvious dimensions of quality, e.g., to detect inconsistencies and incoherence. In addition, bespoke tools have been presented to address the com...

Multiple choice questions (MCQs) are considered highly useful (being easy to take or mark) but quite difficult to create and large numbers are needed to form valid exams and associated practice materials. The idea of re-using an existing ontology to generate MCQs almost suggests itself and has been explored in various projects. In this project, we...

Automated acquisition, or learning, of ontologies has attracted research attention because it can help ontology engineers build ontologies and give domain experts new insights into their data. However, existing approaches to on-tology learning are considerably limited, e.g. focus on learning descriptions for given classes, require intense supervisi...

Automated acquisition, or learning, of ontologies has attracted research attention because it can help ontology engineers build ontologies and give domain experts new insights into their data. However, existing approaches to on-tology learning are considerably limited, e.g. focus on learning descriptions for given classes, require intense supervisi...

Automated acquisition, or learning, of ontologies has attracted research attention because it can help ontology engineers build ontologies and give domain experts new insights into their data. However, existing approaches to on-tology learning are considerably limited, e.g. focus on learning descriptions for given classes, require intense supervisi...

OWL 2 DL is a complex logic with reasoning problems that have a high worst case complexity. Modern reasoners perform mostly very well on naturally occurring ontologies of varying sizes and complexity. This performance is achieved through a suite of complex optimisations (with complex interactions) and elaborate engineering. While the formal basis o...

In recent years, various approaches have been developed for representing and reasoning with exceptions in OWL. The price one pays for such capabilities, in terms of practical performance, is an important factor that is yet to be quantified comprehensively. A major barrier is the lack of naturally occurring ontologies with defeasible features - the...

One shortcoming of classic Descriptions Logics, DLs, is their inability to encode probabilistic knowledge and reason over it. This is, however, a strong demand of some modern applications, e.g. in biology and healthcare. Therefore, probabilistic extensions of DLs are attracting attention nowadays. We introduce the probabilistic DL SHIQP which exten...

One shortcoming of classic Descriptions Logics, DLs, is their inability to encode probabilistic knowledge and reason over it. This is, however, a strong demand of some modern applications, e.g. in biology and healthcare. Therefore, probabilistic extensions of DLs are attracting attention nowadays. We introduce the probabilistic DL SHIQP which exten...

Ontology-based Multiple Choice Question (MCQ) generation has a relatively short history. Many attempts have been carried out to develop methods to generate MCQs from ontologies. However, there is still a need to understand the applicability of these methods in real educational settings. In this paper, we present an empirical evaluation of ontology-...

We present a survey of the current OWL reasoner landscape. Through literature and web search we have identified 35 OWL reasoners that are, at least to some degree, actively maintained. We conducted a survey directly addressing the respective developers, and collected 33 responses. We present an analysis of the survey, characterising all rea-soners...

DL reasoners are complex pieces of software that work on even more complex input which makes manual verification dificult. A single ontology can have hundreds or thousands of classes and thus its classification involve an unsurveyable number of subsumption tests. We propose a new method for debugging classification across multiple rea-soners which...

Several attempts have been already made to develop similarity measures for ontologies. We noticed that some existing similarity measures are ad-hoc and unprincipled. In addition, there is still a need for similarity measures which are applicable to expressive Description Logics and which are terminological. To address these requirements, we have de...

The Atomic Decomposition of an ontology is a succinct representation of the logic-based modules in that ontology. Ultimately, it reveals the modular structure of the ontology. Atomic Decompositions appear to be useful for both user and non-user facing services. For example, they can be used for ontology comprehension and to facilitate reasoner opti...

Tool development for and empirical experimentation in OWL ontology research require a wide variety of suitable ontologies as input for testing and evaluation purposes and detailed characterisations of real on-tologies. Findings of surveys and results of benchmarking activities may be biased, even heavily, towards manually assembled sets of " someho...

The preferential approach to nonmonotonic reasoning was consolidated in depth by Krause, Lehmann and Magidor (KLM) for propositional logic in the early 90’s. In recent years, there have been efforts to extend their framework to Description Logics (DLs) and a solid (though preliminary) theoretical foundation has already been established towards this...

The preferential approach to nonmonotonic reasoning was consolidated in depth by Krause, Lehmann and Magidor (KLM) for propositional logic in the early 90’s. In recent years, there have been efforts to extend their framework to Description Logics (DLs) and a solid theoretical foundation has already been established towards this aim. Despite this fo...

Case-based reasoning (CBR) based on description logics (DLs) has gained a lot of attention lately. Adaptation is a basic task in the CBR inference that can be modeled as the knowledge base revision problem and solved in propositional logic. However, in DLs, it is still a challenge problem since existing revision operators only work well for strictl...

Very expressive Description Logics in the SH family have worst case complexity ranging from EXPTIME to double NEXPTIME. In spite of this, they are very popular with modellers and serve as the foundation of the Web Ontology Language (OWL), a W3C standard. Highly optimised reasoners handle a wide range of naturally occurring ontologies with relative...

Ontologies with potential educational value are available in di?erent domains. However, it is still unclear how such ontologies can be exploited to generate useful instructional content, e.g., assessment questions. In this paper, we present an approach to automatically generate multiple-choice questions from OWL ontologies. We describe a psychologi...

Justifications are the dominant form of explanation for entailments of OWL ontologies, with popular OWL ontology editors, such as Protege 4, providing justification-based explanation facilities. A justification is a minimal subset of an ontology which is sufficient for an entailment to hold; they correspond to the premises of a proof. Unlike proofs...

Given the high expressivity of the Web Ontology Language OWL 2, there is a potential for great diversity in the logical content of OWL ontologies. The fact that many naturally occurring entailments of such ontologies have multiple justifications indicates that ontologies often overdetermine their consequences, suggesting a diversity in supporting r...

For ontology reuse and integration, a number of approaches have been devised that aim at identifying modules, i.e., suitably small sets of “relevant” axioms from ontologies. Here we consider three logically sound notions of modules: MEX modules, only applicable to inexpressive ontologies; modules based on semantic locality, a sound approximation of...

Several attempts have already been made to automate the generation of assessment questions. These attempts were mainly technical and lacked a theoretical backing. We explore psychological and educational theories to support the development of principled methods to generate questions and control their properties. We present a similarity-based theory...

In spite of the recent renaissance in lightweight description logics (DLs), many prominent DLs, such as that underlying the Web Ontology Language (OWL), have high worst case complexity for their key inference services. Modern reasoners have a large array of optimization, tuned calculi, and implementation tricks that allow them to perform very well...

Understanding ontology evolution is becoming an active topic of interest for ontology engineers, e.g., there exist large collaboratively-developed ontologies but, unlike in software engineering, comparatively little is understood about the dynamics of historical changes, especially at a fine level of granularity. Only recently has there been a syst...

In this paper we present the diff tool ecco, which detects changes to both axioms and concepts between OWL ontologies. Furthermore, the tool aligns axiom changes between each other, according to a fine-grained change categorisation, and subsequently aligns axiom changes with the concepts that each of those directly affect. The diff is open source,...

Due to the high worst case complexity of the core reasoning problem for the expressive profiles of OWL 2, ontology engineers are often surprised and confused by the performance behaviour of reasoners on their ontologies. Even very experienced modellers with a sophisticated grasp of reasoning algorithms do not have a good mental model of reasoner pe...

This paper presents an evaluation of state of the art black box justification finding algorithms on the NCBO BioPortal ontology corpus. This corpus represents a set of naturally occurring ontologies that vary greatly in size and expressivity. The results paint a picture of the performance that can be expected when finding all justifications for ent...

Detecting, much less understanding, the difference between two description logic based ontologies is challenging for ontology engi-neers due, in part, to the possibility of complex, non-local logic effects of axiom changes. First, it is often quite difficult to even determine which concepts have had their meaning altered by a change. Second, once a...

Different computational models for generating analogies of the form "A is to B as C is to D" have been proposed over the past 35 years. However, analogy generation is a challenging problem that requires further research. In this article, we present a new approach for generating analogies in Multiple Choice Question (MCQ) format that can be used for...

Extracting a subset of a given OWL ontology that captures all the ontology's knowledge about a specified set of terms is a well-understood task. This task can be based, for instance, on locality-based modules (LBMs). These come in two flavours, syntactic and semantic, and a syntactic LBM is known to contain the corresponding semantic LBM. For synta...

The detection and presentation of changes between OWL ontologies (in the form of a diff) is an important service for ontology engineering, being an active research topic. In this paper, we present a diff tool that incorporates structural and semantic techniques in order to, firstly, distinguish effectual and ineffectual changes between ontolo-gies...

The goal of CEDAR was to bring together researchers interested in problems at the interface between automated reasoning and computational complexity, in particular in: – identifying (fragments of) logical theories which are decidable, resp. have low complexity, and analyzing possibilities of obtaining optimal complexity results with uniform tools;...

This paper provides a review of the state-of-the-art in automatic assessment generation. The paper focuses on and further develops methods for automatic generation of assessments from ontologies. We describe a novel approach and evaluate it by comparing it to other existing approaches. In addition, we report on our experience to evaluate the genera...

In this paper we investigate representation of the part-whole relationship in SNOMED CT. We discuss the current approach, based on "SEP" triples, and several translations of it, which involve DLs at different levels of expressivity. We intend that our analysis will concretely inform the SNOMED community about the important tradeoffs of expressivity...

In this paper, we propose a new approach to generate anal-ogy questions of the form "A is to B as ... is to ?" from ontologies. Analogy questions are widely used in multiple-choice tests such as SATs and GREs and are used to assess student's higher cognitive abilities. The design, implementation and evaluation of the new approach are pre-sented in...

Most ontology development environments (ODEs) are term oriented and take a frame-based view of the information in an ontology about a given term. Even tools, such as Protégé 4, designed for axiom oriented development preserve the frame-based view as the central mode of interaction with the ontology. The frame-based approach has a number of advantag...

This paper presents a characterisation of and definitions for the phenomenon of masking in the context of justifications for entailments in ontologies. In essence masking is present within a justification, over a set of justifications, or over a complete ontology when the number of justifications for an entailment does not reflect the number of rea...

The analysis of changes between OWL ontologies (in the form of a diff) is an important service for ontology engineering. A purely syntactic analysis of changes is insufficient to distinguish between changes that have logical impact and those that do not. The current state of the art in semantic diffing ignores logically ineffectual changes and lack...

Conjunctive queries play an important role as an expressive query language for Description Logics (DLs). Although modern DLs usually provide for transitive roles, conjunctive query answering over DL knowledge bases is only poorly understood if transitive roles are admitted in the query. In this paper, we consider unions of conjunctive queries over...

The analysis of changes between OWL ontologies (in the form of a diff ) is an important service for ontology engineering. A purely syntactic analysis of changes is insufficient to distinguish between changes that have logical impact and those that do not. The current state of the art in semantic diffing ignores logically ineffectual changes and lac...

We present the first large scale investigation into the modular structure of a substantial collection of state-of-the-art biomedical ontolo-gies, namely those maintained in the NCBO BioPortal repository. 5 Using the notion of Atomic Decomposition, we partition BioPortal ontologies into logically coherent subsets (atoms), which are related to each o...

In this paper we examine several forms of modularity in logics as a basis for various conceptions of the topical structure of an ontology. Intuitively, a topic is a coherent fragment of the subject matter of the ontology. Different topics may play different roles: e.g., the main topic (or topics), side topics, or subtopics. If, at the lowest level,...

The National Cancer Institute (NCI) Thesaurus (NCIt) is a biomedical ontology which has been developed for over a decade. Nearly every month from 2003 through 2011, the NCI has published an updated version of the NCIt to the Web as an OWL ontology (as well as in other formats). We collected all 88 OWL versions of the NCIt available and conducted a...

Java is a widespread object-oriented programming language for implementing information systems because it provides means to express various domains of interest. Nevertheless, some fields like Health Care and Life Sciences are so complex that Java is not suited for their design. In comparison, the Web Ontology Language (OWL) provides various powerfu...

Information systems should be designed to allow users to express their information requests in a simple way and to retrieve information that they consider as relevant to these requests. In order to fulfil these requirements, information system designers face many challenges w.r.t. selecting appropriate technologies and deciding on a modelling appro...

Extracting a subset of a given ontology that captures all the ontology's knowledge about a specified set of terms is a well-understood task. This task can be based, for instance, on locality-based modules. However, a single module does not allow us to understand neither topicality, connectedness, structure, or superfluous parts of an ontology, nor...

The detection of changes between OWL ontologies is an important service for ontology engineering. There are several approaches to this problem, both syntactic and semantic. A purely syntactic analysis of changes is insufficient to detect changes with logical effect, while the current state of the art in semantic diffing ignores logically ineffectua...

The canonical standard description logic reasoning service is classification, that is, the generation of the set of atomic subsumptions which are entailed by some ontology. While this consequence relation is well defined and finite, there is significant variance in the composition of that set. For example, it is common (in tools and in discussion)...

Current ontology development tools offer debugging support by presenting justifications for entailments of OWL ontologies. While these minimal subsets have been shown to support debugging and understanding tasks, the occurrence of multiple justifications presents a significant cognitive challenge to users. In many cases even a single entailment may...

In this paper, we present an approach to determining the cognitive complexity of justifications for entailments of OWL ontologies. We introduce a simple cognitive complexity model and present the results of validating that model via experiments involving OWL users. The validation is based on test data derived from a large and diverse corpus of natu...

Extracting a subset of a given ontology that captures all the ontology's knowledge about a specified set of terms is a well-understood task. This task can be based, for instance, on locality-based modules. However, a single module does not allow us to understand neither topic-ality, connectedness, structure, or superfluous parts of an ontology, nor...

Information system designers face many challenges w.r.t. selecting appropriate semantic technologies and deciding on a modelling approach for their system. However, there is no clear methodology yet to evaluate "semantically enriched" information systems. In this paper we present a case study on different modelling approaches for annotating medical...

Analysing the performance of OWL reasoners on expressive OWL ontologies is an ongoing challenge. In this paper, we present a new approach to performance analysis based on justifications for entailments of OWL ontologies. Justifications are minimal subsets of an ontology that are sufficient for an entailment to hold, and are commonly used to debug O...

Justifications — that is, minimal entailing subsets of an ontology — are currently the dominant form of explanation provided by ontology engineering environments, especially those focused on the Web Ontology Language (OWL). Despite this, there are naturally occurring justifications that can be very difficult to understand. In essence, justification...

Efficiently extracting a module from a given ontology that captures all the ontology's knowledge about a set of specified terms is a well-understood task. This task can be based, for instance, on locality-based modules. In contrast, extracting all modules of an ontology is computationally difficult because there can be exponentially many. However,...

This paper presents a discussion on the phenomena of mask- ing in the context of justifications for entailments. Various types of mask- ing are introduced and a definition for each type is given.

Ontology-based data access has received a lot of attention recently, yet there is no clear methodology to evaluate a "semantically enriched" information system in general or an ontology based data ac-cess system in particular. The quality of such an information system clearly depends on how well your data fits your class-level ontology, and how wel...

OWL: Experiences and Directions, 7th International Workshop. 21-22 June 2010, San Francisco, California, USA Objects can be said to be structured when their representation also contains their parts. While OWL in general can describe structured objects, description graphs are a recent, decidable extension to OWL which support the description of clas...

Justifications play a central role as the basis for explaining entailments in OWL ontologies. While techniques for computing justifications for entailments in consistent ontologies are theoretically and practically well-understood, little is known about the practicalities of computing justifications for inconsistent ontologies. This is despite the...

Research about ontology access, processing, and usage paves the way for realizing important tasks in future applications requiring well-understood formal representation formalisms as well as efficient and industrial-strength implementations. In this report, we summarize the state of the art for most important application tasks of this kind that use...

Description logics (DLs) are a family of state-of-the-art knowledge representation languages, and their expressive power has been carefully crafted to provide useful knowledge modeling primitives while allowing for practically effective decision procedures for the basic reasoning problems. Recent experience with DLs, however, has shown that their e...

There are various techniques for specifying a module of an on- tology that covers all knowledge about a given set of terms. These dier with respect to the size of the module, the complexity of its computa- tion, and certain robustness properties. In this paper, we survey existing logic-based approaches, focus on syntactic approximations, and compar...

In this chapter, we explain what description logics are and why they make good ontology languages. In particular, we introduce the description logic SHIQ, which has formed the basis of several well-known ontology languages including OIL, DAML+OIL and OWL. We argue that, without the last decade of basic research in description logics, this family of...

Despite similarities between the Web Ontology Language (OWL) and schema languages traditionally used in relational databases, systems based on these languages exhibit quite different behavior in practice. The schema statements in relational databases are usually interpreted as integrity constraints and are used to check whether the data is structur...

We present a formal framework for (minimal) mod- ule extraction based on an abstract notion of in- separability w.r.t. a signature between ontologies. Two instances of this framework are discussed in detail for DL-Lite ontologies: concept inseparabil- ity, when ontologies imply the same complex con- cept inclusions over the signature, and query in-...

In this paper, we describe an approach for ontology comprehension support called model exploration in which models for ontologies are generated and presented interactively. We also discuss the issues involved in using tableau reasoners for the generation of models for model exploration and report on a user study we conducted on our prototype implem...

This paper analyzes the probabilistic description logic P- SHIQ by looking at it as a fragment of probabilistic rst-order logic with semantics based on possible worlds. We argue that this is an ap- propriate way of investigating its properties and developing extensions. We show how the previously made arguments about dierent types of rst-order prob...

The Family History Knowledge Base (FHKB) was presented at OWLED in 2008. The FHKB uses a rich object property hierarchy, including many OWL 2 features, to derive many entailments on some 450 individuals representing the Stevens family. In the ABox, only par- ent relationships and some sibling relationships (either isSisterOf or isBrotherOf) are ass...

Medical research and clinical workflows often involve collaboration between various institutions. Therefore, ontologies such as SNOMED CT 1 or the Foundational Model of Anatomy (FMA) 2 have gained acceptance as an important tool for a common standard of communication. Medical images are often stored in

The current OWL2 specification provides mechanisms for im- porting whole ontologies. This paper discusses the import of only a mod- ule of an external ontology, which is specified by a set of terms (classes and properties) and defined in such a way that it contains "all knowledge" of the external ontology about these terms. We discuss possible desi...