Research Publications

We modeled expert knowledge of arthropod flower-visiting behavioral ecology and represented this in an event-centric domain ontology, which we describe along with the ontology construction process. Two smaller domain ontologies were created to represent expert knowledge of known flower-visiting insect groups and expert knowledge of the flower-visiting behavioral ecology of Rediviva bees. Two application ontologies were designed, which, together with the domain ontologies, constituted the ontology framework of a prototype semantic enrichment and mediation system that we designed and implemented to improve semantic interoperability between flower-visiting data-stores. We describe and evaluate the system implementation in a case-study of three flower-visiting data-stores, and we discuss the system’s scalability, extension and potential impact. We demonstrate how the system is able to dynamically extract complex ecological interactions from heterogeneous specimen data-stores. The conceptual stance and modeling approach are potentially of general use in representing knowledge of animal behavior and ecological interactions, and in engineering semantic interoperability between data-stores containing behavioral ecology data.

@article{81,
  author = {Willem Coetzer and Deshen Moodley and Aurona Gerber},
  title = {A knowledge-based system for discovering ecological interactions  in biodiversity data-stores of heterogeneous specimen-records:  A case-study of flower-visiting ecology},
  abstract = {We modeled expert knowledge of arthropod flower-visiting behavioral ecology and represented this in an event-centric domain ontology, which we describe along with the ontology construction process. Two smaller domain ontologies were created to represent expert knowledge of known flower-visiting insect groups and expert knowledge of the flower-visiting behavioral ecology of Rediviva bees. Two application ontologies were designed, which, together with the domain ontologies, constituted the ontology framework of a prototype semantic enrichment and mediation system that we designed and implemented to improve semantic interoperability between flower-visiting data-stores. We describe and evaluate the system implementation in a case-study of three flower-visiting data-stores, and we discuss the system’s scalability, extension and potential impact. We demonstrate how the system is able to dynamically extract complex ecological interactions from heterogeneous specimen data-stores. The conceptual stance and modeling approach are potentially of general use in representing knowledge of animal behavior and ecological interactions, and in engineering semantic interoperability between data-stores containing behavioral ecology data.},
  year = {2014},
  journal = {Ecological Informatics},
  publisher = {Elsevier},
}

The formal definition of abduction asks what needs to be added to a knowledge base to enable an observation to be entailed. TBox abduction in description logics (DLs) asks what TBox axioms need to be added to a DL knowledge base to allow a TBox axiom to be entailed. We describe a sound and complete algorithm, based on the standard DL tableau, that takes a TBox abduction problem in ALC and generates solutions in a restricted language. We then show how this algorithm can be enhanced to deal with a broader range of problems in ALC.

@misc{80,
  author = {Ken Halland and Katarina Britz},
  title = {TBox abduction in ALC using a DL tableau},
  abstract = {The formal definition of abduction asks what needs to be
added to a knowledge base to enable an observation to be entailed. TBox
abduction in description logics (DLs) asks what TBox axioms need to
be added to a DL knowledge base to allow a TBox axiom to be entailed.
We describe a sound and complete algorithm, based on the standard DL
tableau, that takes a TBox abduction problem in ALC and generates
solutions in a restricted language. We then show how this algorithm can
be enhanced to deal with a broader range of problems in ALC.},
  year = {2014},
}

A logic for specifying probabilistic transition systems is presented. Our perspective is that of agents performing actions. A procedure for deciding whether sentences in this logic are valid is provided. One of the main contributions of the paper is the formulation of the decision procedure: a tableau system which appeals to solving systems of linear equations. The tableau rules eliminate propositional connectives, then, for all open branches of the tableau tree, systems of linear equations are generated and checked for feasibility. Proofs of soundness, completeness and termination of the decision procedure are provided.

@article{79,
  author = {Gavin Rens and Tommie Meyer and G. Lakemeyer},
  title = {SLAP: Specification logic of actions with probability},
  abstract = {A logic for specifying probabilistic transition systems is presented. Our perspective is that of agents performing actions. A procedure for deciding whether sentences in this logic are valid is provided. One of the main contributions of the paper is the formulation of the decision procedure: a tableau system which appeals to solving systems of linear equations. The tableau rules eliminate propositional connectives, then, for all open branches of the tableau tree, systems of linear equations are generated and checked for feasibility. Proofs of soundness, completeness and termination of the decision procedure are provided.},
  year = {2014},
  journal = {Journal of Applied Logic},
  volume = {12},
  pages = {128-150},
  issue = {2},
  publisher = {Elsevier},
  isbn = {ISSN: 1570-8683},
}

We investigate the requirements for specifying the behaviors of actions in a stochastic domain. That is, we propose how to write sentences in a logical language to capture a model of stochastic transitions due to the execution of actions of some agent. We propose a definition for `proper' and `complete' probabilistic transition model specifications and suggest which assumptions can and perhaps should be made about such specifications to make them more parsimonious. Making a priori or default assumptions about the nature of transitions is useful when a given transition model is not fully specified. Two default assumption approaches will be considered.

@misc{78,
  author = {Gavin Rens and Tommie Meyer and G. Lakemeyer},
  title = {Dealing with Incomplete Transition Information in a Stochastic Action Logic},
  abstract = {We investigate the requirements for specifying the behaviors of actions in a stochastic domain. That is, we propose how to write sentences in a logical language to capture a model of stochastic transitions due to the execution of actions of some agent. We propose a definition for `proper' and `complete' probabilistic transition model specifications and suggest which assumptions can and perhaps should be made about such specifications to make them more parsimonious. Making a priori or default assumptions about the nature of transitions is useful when a given transition model is not fully specified. Two default assumption approaches will be considered.},
  year = {2014},
}

@misc{590,
  author = {Renier van Heerden and Louise Leenen and Barry Irwin},
  title = {Automated Classification of Computer Network Attacks},
  abstract = {},
  year = {2013},
  journal = {5th Workshop on ICT Uses in Warfare and the Safeguarding of Peace (IWSP 2013) at IEEE ICAST 2013},
  month = {2013},
  address = {Pretoria, South Africa},
}

@{589,
  author = {Joey van Vuuren and Louise Leenen and Jackie Phahlamohlaka and Jannie Zaaiman},
  title = {Development of a South African Cybersecurity Policy Implementation Framework},
  abstract = {},
  year = {2013},
  journal = {Proceedings of the 8th International Conference on Information Warfare (ICIW 2013)},
  month = {March 2013},
  publisher = {Academic Conferences International},
  address = {Denver, United States of America},
}

@{588,
  author = {Louise Leenen and Alex Terlunen},
  title = {A Focussed Dynamic Path Finding Algorithm with Constraints},
  abstract = {},
  year = {2013},
  journal = {IEEE International Conference on Adaptive Science and Technology (ICAST 2013)},
  month = {2013},
  publisher = {IEEE},
  address = {Pretoria, South Africa},
}

Stream reasoning is an emerging research area focusing on the development of reasoning techniques applicable to streams of rapidly changing, semantically enhanced data. In this paper, we consider data represented in Description Logics from the popular DL-Lite family, and study the logic foundations of prediction and explanation over DL-Lite data streams, i.e., reasoning from finite segments of streaming data to conjectures about the content of the streams in the future or in the past. We propose a novel formalization of the problem based on temporal “past-future” rules, grounded in Temporal Query Language. Such rules can naturally accommodate complex data association patterns, which are typically discovered through data mining processes, with logical and temporal constraints of varying expressiveness. Further, we analyse the computational complexity of reasoning with rules expressed in different fragments of the temporal language. As a result, we draw precise demarcation lines between NP-, DP- and PSpace-complete variants of our setting and, consequently, suggest relevant restrictions rendering prediction and explanation more feasible in practice.

@{364,
  author = {Szymon Klarman and Tommie Meyer},
  title = {Prediction and Explanation over DL-Lite Data Streams},
  abstract = {Stream reasoning is an emerging research area focusing on the development of reasoning techniques applicable to streams of rapidly changing, semantically enhanced data. In this paper, we consider data represented in Description Logics from the popular DL-Lite family, and study the logic foundations of prediction and explanation over DL-Lite data streams, i.e., reasoning from finite segments of streaming data to conjectures about the content of the streams in the future or in the past. We propose a novel formalization of the problem based on temporal “past-future” rules, grounded in Temporal Query Language. Such rules can naturally accommodate complex data association patterns, which are typically discovered through data mining processes, with logical and temporal constraints of varying expressiveness. Further, we analyse the computational complexity of reasoning with rules expressed in different fragments of the temporal language. As a result, we draw precise demarcation lines between NP-, DP- and PSpace-complete variants of our setting and, consequently, suggest relevant restrictions rendering prediction and explanation more feasible in practice.},
  year = {2013},
  journal = {International Conference on Logic for Programming, Artificial Intelligence and Reasoning (LPAR-19)},
  pages = {536-551},
  month = {14/12 - 19/12},
  publisher = {Springer},
  url = {https://www.springer.com/gp/book/9783642452208},
}

The introduction of defeasible reasoning in Description Logics has been a main research topic in the field in the last years. Despite the fact that various interesting formalizations of nonmonotonic reasoning for the TBox have been proposed, the application of such a kind of reasoning also to ABoxes is more problematic. In what follows we are going to present the adaptation for the ABox of a classical nonmonotonic form of reasoning, Lehmann and Magidor’s Rational Closure. We present both a procedural and a semantical characterization, and we conclude the paper with a comparison between our and other analogous proposals, and suggesting some possible heuristics useful for the ABox querying procedure.

@misc{114,
  author = {Giovanni Casini and Tommie Meyer and Kody Moodley and Ivan Varzinczak},
  title = {Nonmonotonic reasoning in Description Logics: Rational Closure for the ABox},
  abstract = {The introduction of defeasible reasoning in Description Logics has been a main research topic in the field in the last years. Despite the fact that various interesting formalizations of nonmonotonic reasoning for the TBox have been proposed, the application of such a kind of reasoning also to ABoxes is more problematic. In what follows we are going to present the adaptation for the ABox of a classical nonmonotonic form of reasoning, Lehmann and Magidor’s Rational Closure. We present both a procedural and a semantical characterization, and we conclude the paper with a comparison between our and other analogous proposals, and suggesting some possible heuristics useful for the ABox querying procedure.},
  year = {2013},
}

We introduce Propositional Typicality Logic (PTL), a logic for reasoning about typicality. We do so by enriching classical propositional logic with a typicality operator of which the intuition is to capture the most typical (or normal) situations in which a given formula holds. The semantics is in terms of ranked models as studied in KLM-style preferential reasoning. This allows us to show that KLM-style rational consequence relations can be embedded in our logic. Moreover we show that we can define consequence relations on the language of PTL itself, thereby moving beyond the propositional setting. Building on the existing link between propositional rational consequence and belief revision, we show that the same correspondence holds in the case of rational consequence and belief revision defined on the language of PTL. Finally we also investigate different notions of entailment for PTL and propose two appropriate candidates.

@inbook{85,
  author = {Richard Booth and Tommie Meyer and Ivan Varzinczak},
  title = {A Propositional Typicality Logic for Extending Rational Consequence},
  abstract = {We introduce Propositional Typicality Logic (PTL), a logic for reasoning about typicality. We do so by enriching classical propositional logic with a typicality operator of which the intuition is to capture the most typical (or normal) situations in which a given formula holds. The semantics is in terms of ranked models as studied in KLM-style preferential reasoning. This allows us to show that KLM-style rational consequence relations can be embedded in our logic. Moreover we show that we can define consequence relations on the language of PTL itself, thereby moving beyond the propositional setting. Building on the existing link between propositional rational consequence and belief revision, we show that the same correspondence holds in the case of rational consequence and belief revision defined on the language of PTL. Finally we also investigate different notions of entailment for PTL and propose two appropriate candidates.},
  year = {2013},
  journal = {Trends in Belief Revision and Argumentation Dynamics},
  pages = {1-31},
  publisher = {King's College Publications},
}

We enrich description logics with non-monotonic reasoning features. We start by investigating a notion of defeasible subsumption relation in the spirit of KLM-style defeasible consequence. In particular we provide a natural and intuitive semantics for defeasible subsump- tion in terms of DL interpretations enriched with a preference relation. We propose syntactic characterizations for both preferential and rational subsumption relations (in terms of Gentzen-style rules or postulates) and prove representation results for the description logic ALC. We then move to non-monotonicity in DLs at the level of entailment. We investigate versions of entailment in the context of both preferential and rational subsumption, relate them to preferential and rational closure, and show that computing them can be reduced to classical ALC entailment, pro- viding further evidence that our semantic constructions are appropriate in a non-monotonic DL setting.

@misc{77,
  author = {Giovanni Casini and Tommie Meyer and Ivan Varzinczak and Kody Moodley and Katarina Britz},
  title = {Ordered Interpretations and Entailment for Defeasible Description Logics},
  abstract = {We enrich description logics with non-monotonic reasoning features. We start by investigating a notion of defeasible subsumption relation in the spirit of KLM-style defeasible consequence. In particular we provide a natural and intuitive semantics for defeasible subsump- tion in terms of DL interpretations enriched with a preference relation. We propose syntactic characterizations for both preferential and rational subsumption relations (in terms of Gentzen-style rules or postulates) and prove representation results for the description logic ALC. We then move to non-monotonicity in DLs at the level of entailment. We investigate versions of entailment in the context of both preferential and rational subsumption, relate them to preferential and rational closure, and show that computing them can be reduced to classical ALC entailment, pro- viding further evidence that our semantic constructions are appropriate in a non-monotonic DL setting.},
  year = {2013},
}

As part of the requirements phase of building a software system, a conceptual model could be created which describes the information and processes of the business. This conceptual model is often expressed as a UML class diagram. In an attempt to validate the UML class diagram, stakeholders test various usage scenarios against it. The availablity of formal reasoning procedures will greatly ease finding associated inconsistencies. To date, substantial research has been done on transforming UML class diagrams into different Description Logics. In this paper we explore how Description Logics can be used to fascilitate scenario testing as a means to validate the UML class diagrams. Since identity constraints on UML class diagrams have not been mapped to a Description Logic as yet, we evaluate the suitability of using either DLR_ifd or SROIQ(D) for this purpose.

@misc{76,
  author = {Henriette Harmse and Katarina Britz and Aurona Gerber},
  title = {Scenario Testing on UML Class Diagrams using Description Logic},
  abstract = {As part of the requirements phase of building a software system, a conceptual model could be created which describes the information and processes of the business. This conceptual model is often expressed as a UML class diagram. In an attempt to validate the UML class diagram, stakeholders test various usage scenarios against it. The availablity of formal reasoning procedures will greatly ease finding associated inconsistencies. To date, substantial research has been done on transforming UML class diagrams into different Description Logics. In this paper we explore how Description Logics can be used to fascilitate scenario testing as a means to validate the UML class diagrams. Since identity constraints on UML class diagrams have not been mapped to a Description Logic as yet, we evaluate the suitability of using either DLR_ifd or SROIQ(D) for this purpose.},
  year = {2013},
}

We consider online partially observable Markov decision processes (POMDPs) which compute policies by local look-ahead from the current belief-state. One problem is that belief-nodes deeper in the decision-tree increase in the number of states with non-zero probability they contain. Computation time of updating a belief-state is exponential in the number of states contained by the belief. Belief-update occurs for each node in a search tree. It would thus pay to reduce the size of the nodes while keeping the information they contain. In this paper, we compare four fast and frugal methods to reduce the size of belief-nodes in the search tree, hence improving the running-time of online POMDP algorithms.

@{74,
  author = {Gavin Rens and Alexander Ferrein},
  title = {Belief-node Condensation for Online POMDP Algorithms},
  abstract = {We consider online partially observable Markov decision processes (POMDPs) which compute policies by local look-ahead from the current belief-state. One problem is that belief-nodes deeper in the decision-tree increase in the number of states with non-zero probability they contain. Computation time of updating a belief-state is exponential in the number of states contained by the belief. Belief-update occurs for each node in a search tree. It would thus pay to reduce the size of the nodes while keeping the information they contain. In this paper, we compare four fast and frugal methods to reduce the size of belief-nodes in the search tree, hence improving the running-time of online POMDP algorithms.},
  year = {2013},
  journal = {IEEE AFRICON 2013},
  pages = {1270-1274},
  isbn = {978-1-4673-5940-5},
}

No Abstract

@{73,
  author = {Aurona Gerber and Marne de Vries and Alta van der Merwe},
  title = {Towards an enterprise evolution contextualisation model.},
  abstract = {No Abstract},
  year = {2013},
  journal = {ES 2013 - the first international conference on Enterprise Systems},
  month = {07/11 - 08/11},
  address = {Cape Town},
}

No Abstract

@{72,
  author = {Aurona Gerber and Alta van der Merwe and Kevin Bayes},
  title = {An Investigation into UML Case Tool Support for the Zachman Framework},
  abstract = {No Abstract},
  year = {2013},
  journal = {ES 2013 - the first international conference on Enterprise Systems},
  month = {01/11 - 08/11},
  address = {Cape Town},
}

No Abstract

@{71,
  author = {Aurona Gerber and Alta van der Merwe and Judith van der Linde},
  title = {The Impact of Managerial EA Decisions on Software Development Employees.},
  abstract = {No Abstract},
  year = {2013},
  journal = {ES 2013 - the first international conference on Enterprise Systems},
  month = {07/11 - 08/11},
  address = {Cape Town},
}

We explore a family of supraclassical consequence relations obtained by varying the criteria according to which counterexamples to classical entailment may be deemed tolerable. This provides a dierent perspective on the rational consequence relations of nonmonotonic logic, as well as introducing new kinds of entailment with a diversity of potential contextual applications.

@{70,
  author = {Katarina Britz and W. Labuschagne and J. Heidema},
  title = {Supraclassical consequence relations tolerating rare counter-examples},
  abstract = {We explore a family of supraclassical consequence relations obtained by varying the criteria according to which counterexamples to
classical entailment may be deemed tolerable. This provides a dierent perspective on the rational consequence relations of nonmonotonic logic,
as well as introducing new kinds of entailment with a diversity of potential contextual applications.},
  year = {2013},
  journal = {Australasian Joint Conference on Artificial Intelligence},
  pages = {326-337},
  month = {01/12},
  isbn = {978-3-319-03679-3},
}

We present a decidable logic in which POMDPs can be specied with compact representations, and queries can be posed about (i) the degree of belief in a propositional sentence after an arbitrary nite number of actions and observations and (ii) the utility of a nite sequence of actions after a number of actions and observations. The task of the logic is to check whether a query (stated in the language of the logic) follows from a knowledge base (KB), which is typically a POMDP model specication (also stated in the language of the logic). The main contribution of this work is that the POMDP model specication is allowed to be partial or incomplete with no restriction on the lack of information specied for the model. The KB may even contain information about non-initial beliefs. Essentially, entailment of arbitrary queries (expressible in the language) can be answered. A sound, complete and terminating decision procedure is provided.

@misc{69,
  author = {Gavin Rens and Tommie Meyer and G. Lakemeyer},
  title = {The Stochastic Decision Logic},
  abstract = {We present a decidable logic in which POMDPs can be specied with compact representations, and queries can be posed about (i) the degree of belief in a propositional sentence after an arbitrary nite number of actions and observations and (ii) the utility of a nite sequence of actions after a number of actions and observations. The task of the logic is to check whether a query (stated in the language of the logic) follows from a knowledge base (KB), which is typically a POMDP model specication (also stated in the language of the logic). The main contribution of this work is that the POMDP model specication is allowed to be partial or incomplete with no restriction on the lack of information specied for the model. The KB may even contain information about non-initial beliefs. Essentially, entailment of arbitrary queries (expressible in the language) can be answered. A sound, complete and terminating decision procedure is provided.},
  year = {2013},
}

No Abstract

@misc{68,
  author = {Willem Coetzer and Deshen Moodley and Aurona Gerber},
  title = {Implementing a semantic mediator to integrate flower-visiting records from South African natural history museums},
  abstract = {No Abstract},
  year = {2013},
}

In the field of non-monotonic logics, the notion of rational closure is acknowledged as a landmark and we are going to see whether such a construction can be adopted in the context of mathematical fuzzy logic, a so far (apparently) unexplored journey. As a first step, we will characterise rational closure in the context of Propositional Godel Logic.

@{67,
  author = {Giovanni Casini and Umberto Straccia},
  title = {Towards Rational Closure for Fuzzy Logic: The Case of  Propositional Godel Logic},
  abstract = {In the field of non-monotonic logics, the notion of rational closure is acknowledged as a landmark and we are going to see whether such a construction can be adopted in the context of mathematical fuzzy logic, a so far (apparently) unexplored journey. As a first step, we will characterise rational closure in the context of Propositional Godel Logic.},
  year = {2013},
  journal = {LPAR-19},
  month = {14/12 - 19/12},
  isbn = {978-3-642-45221-5},
}

The Object Role Modeling language (ORM2) is nowadays the most widespread fact-based conceptual modeling language in the business world. Recently, it has been proposed an encoding of the core fragment of ORM2 (called ORM2zero) into the description logic ALCQI, allowing the use of reasoning technologies in the analysis of the schemas. A number of services have been defined there based on the FO semantics of ORM2. On the other hand, in many application domains there is a need for the formalization and modeling of defeasible information and non-monotonic reasoning services. Here we formalize a possible way of introducing non-monotonic reasoning into ORM2 schemas, enriching the language with a special set of new constraints.

@misc{66,
  author = {Giovanni Casini and A. Mosca},
  title = {Non-monotonic reasoning in conceptual modeling and ontology design: A proposal.},
  abstract = {The Object Role Modeling language (ORM2) is nowadays the most widespread fact-based conceptual modeling language in the business world. Recently, it has been proposed an encoding of the core fragment of ORM2 (called ORM2zero) into the description logic ALCQI, allowing the use of reasoning technologies in the analysis of the schemas. A number of services have been defined there based on the FO semantics of ORM2. On the other hand, in many application domains there is a need for the formalization and modeling of defeasible information and non-monotonic reasoning services. Here we formalize a possible way of introducing non-monotonic reasoning into ORM2 schemas, enriching the language with a special set of new constraints.},
  year = {2013},
  isbn = {978-3-642-38489-9},
  url = {http://link.springer.com/chapter/10.1007%2F978-3-642-38490-5_34},
}

Defeasible inheritance networks are a non-monotonic framework that deals with hierarchical knowledge. On the other hand, rational closure is acknowledged as a landmark of the preferential approach to non-monotonic reasoning. We will combine these two approaches and define a new non-monotonic closure operation for propositional knowledge bases that combines the advantages of both. Then we redefine such a procedure for Description Logics (DLs), a family of logics well-suited to model structured information. In both cases we will provide a simple reasoning method that is built on top of the classical entailment relation and, thus, is amenable of an implementation based on existing reasoners. Eventually, we evaluate our approach on well-known landmark test examples.

@article{64,
  author = {Giovanni Casini and Umberto Straccia},
  title = {Defeasible Inheritance-based Description Logics},
  abstract = {Defeasible inheritance networks are a non-monotonic framework that deals with hierarchical knowledge. On the other hand, rational closure is acknowledged as a landmark of the preferential approach to non-monotonic reasoning. We will combine these two approaches and define a new non-monotonic closure operation for propositional knowledge bases that combines the advantages of both. Then we redefine such a procedure for Description Logics (DLs), a family of logics well-suited to model structured information. In both cases we will provide a simple reasoning method that is built on top of the classical entailment relation and, thus, is amenable of an implementation based on existing reasoners. Eventually, we evaluate our approach on well-known landmark test examples.},
  year = {2013},
  journal = {Journal of Artificial Intelligence Reasearch},
  volume = {48},
  pages = {415-473},
  publisher = {AAAI Press},
  isbn = {1076 - 9757},
}

Consolidating currently fragmented health information systems in low and middle-income countries (LMIC) into a coherent national information system will increase operational efficiencies, improve decision-making and will lead to better health outcomes. However, engineering an enterprise information system of the scale and complexity of a national health information system (NHIS) pose unique and complex challenges in LMICs. In this paper, we review current approaches to NHIS development and discuss challenges faced by LMICs to develop their NHIS. Based on current LMIC systems we identify three stages of system evolution and propose that LMICs should follow an evolutionary, middle-out approach to NHIS development supported by appropriate architectural frameworks.

@{63,
  author = {Thinasagree Mudaly and Deshen Moodley and Anban Pillay and Chris Seebregts},
  title = {Architectural Frameworks for Developing National Health Information Systems in Low and Middle Income Countries},
  abstract = {Consolidating currently fragmented health information systems in low and middle-income countries (LMIC) into a coherent national information system will increase operational efficiencies, improve decision-making and will lead to better health outcomes. However, engineering an enterprise information system of the scale and complexity of a national health information system (NHIS) pose unique and complex challenges in LMICs. In this paper, we review current approaches to NHIS development and discuss challenges faced by LMICs to develop their NHIS. Based on current LMIC systems we identify three stages of system evolution and propose that LMICs should follow an evolutionary, middle-out approach to NHIS development supported by appropriate architectural frameworks.},
  year = {2013},
  journal = {Proceedings of the First IEEE International Conference on Enterprise Systems (ES 2013), Cape Town, South Africa},
  month = {07/11 - 08/11},
}

No Abstract

@{62,
  author = {Willem Coetzer and Deshen Moodley and Aurona Gerber},
  title = {A Case-Study of Ontology-Driven Semantic Mediation of Flower-Visiting Data from Heterogeneous Data-Stores in Three South African Natural History Collections},
  abstract = {No Abstract},
  year = {2013},
  journal = {The Semantic Web: ESWC 2013 Satellite Events},
  pages = {87-100},
  month = {05/27},
  address = {Berlin},
}

In this paper we investigate module extraction for the Description Logic SRIQ. We formulate modules in terms of the reachability problem for directed hypergraphs. Using inseparability relations, we investigate the module-theoretic properties of reachability modules and show by means of an empirical evaluation that these modules have the potential of being substantially smaller than syntactic locality modules.

@{60,
  author = {Riku Nortjé and Katarina Britz and Tommie Meyer},
  title = {Reachability modules for the Description Logic SRIQ},
  abstract = {In this paper we investigate module extraction for the Description Logic SRIQ. We formulate modules in terms of the reachability problem for directed hypergraphs. Using inseparability relations, we
investigate the module-theoretic properties of reachability modules and
show by means of an empirical evaluation that these modules have the
potential of being substantially smaller than syntactic locality modules.},
  year = {2013},
  journal = {LPAR},
}