Research Publications

@misc{597,
  author = {W.A. Labuschagne and M.M. Eloff and Namosha Veerasamy and Louise Leenen and Mathias Mujinga},
  title = {Design of a Cyber Security Awareness Campaign for Internet Cafe Users in Rural Areas},
  abstract = {},
  year = {2011},
  journal = {Proceedings of the First IFIP TC9/TC11 Southern African Cyber Security Awareness Workshop (SACSAW 2011)},
  month = {12 May 2011},
  address = {Gaborone, Botswana},
}

In this paper we describe a research project to develop an optimal information retrieval system in an Information Operations domain. Information Operations is the application and management of information to gain an advantage over an opponent and to defend one’s own interests. Corporations, governments, and military forces are facing increasing exposure to strategic information-based actions. Most national defence and security organisations regard Information Operations as both a defensive and offensive tool, and some commercial institutions are also starting to recognise the value of Information Operations. An optimal information retrieval system should have the capability to extract relevant and reasonably complete information from different electronic data sources which should decrease information overload. Information should be classified in a way such that it can be searched and extracted effectively. The authors of this paper have completed an initial phase in the investigation and design of a knowledge system that can be used to extract relevant and complete knowledge for the planning and execution of Information Operations. During this initial phase of the project, we performed a needs analysis and problem analysis and our main finding is the recommendation of the use of logic-based ontologies: it has the advantage of an unambiguous semantics, facilitates intelligent search, provides an optimal trade-off between expressivity and complexity, and yields optimal recall of information. The risk of adopting this technology is its status as an emerging technology and therefore we include recommendations for the development of a prototype system.

@{465,
  author = {Louise Leenen and Ronell Alberts and Katarina Britz and Aurona Gerber and Tommie Meyer},
  title = {Developing a Knowledge System for Information Operations},
  abstract = {In this paper we describe a research project to develop an optimal information retrieval system in an Information Operations domain. Information Operations is the application and management of information to gain an advantage over an opponent and to defend one’s own interests. Corporations, governments, and military forces are facing increasing exposure to strategic information-based actions. Most national defence and security organisations regard Information Operations as both a defensive and offensive tool, and some commercial institutions are also starting to recognise the value of Information Operations. An optimal information retrieval system should have the capability to extract relevant and reasonably complete information from different electronic data sources which should decrease information overload. Information should be classified in a way such that it can be searched and extracted effectively. The authors of this paper have completed an initial phase in the investigation and design of a knowledge system that can be used to extract relevant and complete knowledge for the planning and execution of Information Operations. During this initial phase of the project, we performed a needs analysis and problem analysis and our main finding is the recommendation of the use of logic-based ontologies: it has the advantage of an unambiguous semantics, facilitates intelligent search, provides an optimal trade-off between expressivity and complexity, and yields optimal recall of information. The risk of adopting this technology is its status as an emerging technology and therefore we include recommendations for the development of a prototype system.},
  year = {2011},
  journal = {6th International Conference on Information Warfare and Security},
  month = {17/03-18/03},
  address = {Washington D.C., United States of America},
  isbn = {978-1-906638-93-1},
  doi = {10204/4951},
}

The purpose of accounting is to gather financial data of a business or entity,to interpret this data and to report the results in financial statements to the different users thereof. The interpretation off financial data is regulated by financial accounting standards including a conceptual framework that we redeveloped to facilitate the reporting of financial information of entities. Due to the history of standards development as well as the mechanisms used, inconsistencies in the standards, framework and interpretations are part of the common legacy accountants are confronted with everyday. The development of unambiguous and principle based financial accounting standards is therefore a key initiative at present of international accounting standards bodies such as the FASB and the IASB. This paper is concerned with the question of how recently developed computer science technologies could assist in dealing with and eliminating inconsistencies and ambiguities within and between different financial accounting standards. In our research we developed a formal ontology for some of the basic elements, and in this paper we report on our findings as well as make some suggestions for a formal approach to the conceptual framework and financial accounting standards development.

@{464,
  author = {Marthinus Gerber and Aurona Gerber and Alta van der Merwe},
  title = {Using Formal Ontologies for the Development of Consistent and Unambiguous Financial Accounting Standards},
  abstract = {The purpose of accounting is to gather financial data of a business or entity,to interpret this data and to report the results in financial statements to the different users thereof. The interpretation off financial data is regulated by financial accounting standards including a conceptual framework that we redeveloped to facilitate the reporting of financial information of entities. Due to the history of standards development as well as the mechanisms used, inconsistencies in the standards, framework and interpretations are part of the common legacy accountants are confronted with everyday. The development of unambiguous and principle based financial accounting standards is therefore a key initiative at present of international accounting standards bodies such as the FASB and the IASB. This paper is concerned with the question of how recently developed computer science technologies could assist in dealing with and eliminating inconsistencies and ambiguities within and between different financial accounting standards. In our research we developed a formal ontology for some of the basic elements, and in this paper we report on our findings as well as make some suggestions for a formal approach to the conceptual framework and financial accounting standards development.},
  year = {2011},
  journal = {3rd International Joint Conference on Knowledge Discovery, Knowledge Engineering and Knowledge Management},
  month = {24/10-26/10},
  address = {Paris, France},
}

The purpose of accounting is to gather financial data of a business or entity, to interpret this data and to report the results in financial statements to the different users thereof. The interpretation of financial data is regulated by financial accounting standards including an conceptual framework that were developed to facilitate the reporting of financial information of entities so that investors, analysts, creditors as well as the entities themselves can make informed financial decisions. Due to the history as well as some of the mechanisms used to develop the financial accounting standards, conceptual framework and interpretations, inconsistencies and ambiguities are part of the common legacy accountants and auditors are confronted with every day. This is problematic because financial reports have to be clear, concise and unambiguous as the cornerstone of international economies. In order to address the inconsistency problems, the development of unambiguous and principle based financial accounting standards is a key initiative of international financial accounting standards bodies such as the FASB and the IASB at present. This paper is concerned with the question of how recent developments in computer science technologies, specifically within knowledge representation and ontology technologies, could assist in dealing with and eliminating inconsistencies and ambiguities within and between different financial accounting standards. In our research, we developed a formal ontology for some of the basic elements, and in this paper, we report on our findings as well as make some suggestions for a formal approach to the conceptual framework and financial accounting standards development.

@{463,
  author = {Marthinus Gerber and Aurona Gerber},
  title = {Towards the Development of Consistent and Unambiguous Financial Accounting Standards using Ontology Technologies},
  abstract = {The purpose of accounting is to gather financial data of a business or entity, to interpret this data and to report the results in financial statements to the different users thereof. The interpretation of financial data is regulated by financial accounting standards including an conceptual framework that were developed to facilitate the reporting of financial information of entities so that investors, analysts, creditors as well as the entities themselves can make informed financial decisions. Due to the history as well as some of the mechanisms used to develop the financial accounting standards, conceptual framework and interpretations, inconsistencies and ambiguities are part of the common legacy accountants and auditors are confronted with every day. This is problematic because financial reports have to be clear, concise and unambiguous as the cornerstone of international economies. In order to address the inconsistency problems, the development of unambiguous and principle based financial accounting standards is a key initiative of international financial accounting standards bodies such as the FASB and the IASB at present. This paper is concerned with the question of how recent developments in computer science technologies, specifically within knowledge representation and ontology technologies, could assist in dealing with and eliminating inconsistencies and ambiguities within and between different financial accounting standards. In our research, we developed a formal ontology for some of the basic elements, and in this paper, we report on our findings as well as make some suggestions for a formal approach to the conceptual framework and financial accounting standards development.},
  year = {2011},
  journal = {International Association for Accounting Education & Research},
  month = {03/11-05/11},
  address = {Venice, Italy},
}

n.a.

@misc{462,
  author = {Johann Bergh and Aurona Gerber and Tommie Meyer and Lynette van Zijl},
  title = {Path analysis for ontology comprehension},
  abstract = {n.a.},
  year = {2011},
  journal = {Seventh Australasian Ontology Workshop},
  month = {12/11},
}

A key constraint for growing small and medium enterprises (SMEs) is the business skills required to grow the enterprises through the stages of transformation. Criticism against growth stage models for SMEs is of concern, since these models contain the typical knowledge that appeals to managers of small enterprises as guidance in how to manage growth. In this article we propose the SMEAG model to explore the relevance of enterprise architecture (EA) for enhancing existing growth stage models in order to counteract some of this criticism. EA is well-known as a field that claims to manage change and complexity. The rationale to combine the concepts of growth stage models and EA is based on the level of change and complexity associated with the growth of small enterprises into medium enterprises. SMEAG combines the existing growth stage model of Scott and Bruce, the Enterprise Architecture Framework by Hoogervorst, and the EA as Foundation for Business Execution Model by Ross, Weill and Robertson.

@{461,
  author = {Dina Jacobs and Paula Kotzé and Alta van der Merwe and Aurona Gerber},
  title = {Enterprise Architecture for Small and Medium Enterprise Growth},
  abstract = {A key constraint for growing small and medium enterprises (SMEs) is the business skills required to grow the enterprises through the stages of transformation. Criticism against growth stage models for SMEs is of concern, since these models contain the typical knowledge that appeals to managers of small enterprises as guidance in how to manage growth. In this article we propose the SMEAG model to explore the relevance of enterprise architecture (EA) for enhancing existing growth stage models in order to counteract some of this criticism. EA is well-known as a field that claims to manage change and complexity. The rationale to combine the concepts of growth stage models and EA is based on the level of change and complexity associated with the growth of small enterprises into medium enterprises. SMEAG combines the existing growth stage model of Scott and Bruce, the Enterprise Architecture Framework by Hoogervorst, and the EA as Foundation for Business Execution Model by Ross, Weill and Robertson.},
  year = {2011},
  journal = {1st Enterprise Engineering Working Conference},
  pages = {61-75},
  month = {16/05-20/05},
  publisher = {Springer, Berlin, Heidelberg},
  address = {Antwerp, Belgium},
  isbn = {978-3-642-21057-0},
  url = {https://link.springer.com/book/10.1007/978-3-642-21058-7},
  doi = {10.1007/978-3-642-21058-7_5},
}

Enterprise engineering is an enterprise design methodology that uses a process to create an organised whole, while mastering complexity. Dietz proposes an organisation theorem that reduces complexity by representing the heterogeneous enterprise system as a layered integration of three homogeneous aspect systems: the ontological, infological and datalogical. The ontological aspect system represents the essence of enterprise operation and a starting point for engineering a complex enterprise. This paper applies one of the key ontological models, namely the interaction model, to assess its ability to indentify replication potential due to ontological similarity. The case study environment for application of the interaction model was four departments at a tertiary education institution.

@{460,
  author = {Marne de Vries and Alta van der Merwe and Paula Kotzé and Aurona Gerber},
  title = {Using the Interaction model to compare ontological similarity between business units},
  abstract = {Enterprise engineering is an enterprise design methodology that uses a process to create an organised whole, while mastering complexity. Dietz proposes an organisation theorem that reduces complexity by representing the heterogeneous enterprise system as a layered integration of three homogeneous aspect systems: the ontological, infological and datalogical. The ontological aspect system represents the essence of enterprise operation and a starting point for engineering a complex enterprise. This paper applies one of the key ontological models, namely the interaction model, to assess its ability to indentify replication potential due to ontological similarity. The case study environment for application of the interaction model was four departments at a tertiary education institution.},
  year = {2011},
  journal = {1st International Conference on Industrial Engineering, Systems Engineering & Engineering Management for Sustainable Global Development},
  month = {21/09-23/09},
  address = {Stellenbosch, Western Cape, South Africa},
  doi = {10204/5425},
}

Staying competitive in the 21 st century requires enterprise unity and integration, allowing for agility to accommodate swift changes in strategy as markets evolve and new opportunities emerge. The foundation for execution approach acknowledges the volatility of strategy and suggests the use of an operating model (OM), which is a commitment to a way of doing business. The OM creates a company-wide vision for process standardization and data centralization and guides decisions about how a company implements processes and IT infrastructure. Although the OM provides senior management with a powerful decision-making tool in evolving the current IT landscape, the selection of an appropriate OM requires additional guidance. This article elaborates on current OM deficiencies, requirements for enhancement and a new method, mechanisms and practices to enable an enterprise architecture practitioner to identify the required process reuse opportunities for a specific OM.

@{459,
  author = {Marne de Vries and Alta van der Merwe and Paula Kotzé and Aurona Gerber},
  title = {A Method for Identifying Process Reuse Opportunities to Enhance the Operating Model},
  abstract = {Staying competitive in the 21 st century requires enterprise unity and integration, allowing for agility to accommodate swift changes in strategy as markets evolve and new opportunities emerge. The foundation for execution approach acknowledges the volatility of strategy and suggests the use of an operating model (OM), which is a commitment to a way of doing business. The OM creates a company-wide vision for process standardization and data centralization and guides decisions about how a company implements processes and IT infrastructure. Although the OM provides senior management with a powerful decision-making tool in evolving the current IT landscape, the selection of an appropriate OM requires additional guidance. This article elaborates on current OM deficiencies, requirements for enhancement and a new method, mechanisms and practices to enable an enterprise architecture practitioner to identify the required process reuse opportunities for a specific OM.},
  year = {2011},
  journal = {IEEE International Conference on Industrial Engineering and Engineering Management},
  month = {03/09-05/09},
  address = {Changchun, China},
  isbn = {978-1-4577-0739-1},
}

No Abstract

@phdthesis{88,
  author = {Riku Nortjé},
  title = {Module extraction for inexpressive description logics},
  abstract = {No Abstract},
  year = {2011},
  volume = {MSc},
}

No Abstract

@phdthesis{87,
  author = {J. Hastings and Katarina Britz},
  title = {Representing chemical structures using OWL and description graphs},
  abstract = {No Abstract},
  year = {2011},
  volume = {MSc},
}

From studies, it is clear that using a foundational ontology for domain ontology development is beneficial in theory and practice. However, when it is to be used, developers don't know which one to choose and why. In order to solve this problem, a comprehensive set of criteria that in influence foundational ontology selection has been compiled and a corresponding software tool has been developed to help a domain ontology developer to choose one. This report presents ONSET: a tool used for foundational ontology selection in domain ontology development. Based on an ontology developer's preferences such as ontological commitments, representation languages and other factors, ONSET selects an appropriate foundational ontology to be used for the domain ontology to be developed.

@phdthesis{83,
  author = {Zubeida Khan and Maria Keet},
  title = {Extending ontology development methodologies with foundational ontologies},
  abstract = {From studies, it is clear that using a foundational ontology for domain ontology development is beneficial in theory and practice. However, when it is to be used, developers don't know which one to choose and why. In order to solve this problem, a comprehensive set of criteria that in influence foundational ontology selection has been compiled and a corresponding software tool has been developed to help a domain ontology developer to choose one. This report presents ONSET: a tool used for foundational ontology selection in domain ontology development. Based on an ontology developer's preferences such as ontological commitments, representation languages and other factors, ONSET selects an appropriate foundational ontology to be used for the domain ontology to be developed.},
  year = {2011},
  volume = {Honours},
}

In logic-based Knowledge Representation and Reasoning (KRR), ontologies are used to represent knowledge about a particular domain of interest in a precise way. The building blocks of ontologies include concepts, relations and objects. Those can be combined to form logical sentences which explicitly describe the domain. With this explicit knowledge one can perform reasoning to derive knowledge that is implicit in the ontology. Description Logics (DLs) are a group of knowledge representation languages with such capabilities that are suitable to represent ontologies. The process of building ontologies has been greatly simplied with the advent of graphical ontology editors such as SWOOP, Protege and OntoStudio. The result of this is that there are a growing number of ontology engineers attempting to build and develop ontologies. It is frequently the case that errors are introduced while constructing the ontology resulting in undesirable pieces of implicit knowledge that follows from the ontology. As such there is a need to extend current ontology editors with tool support to aid these ontology engineers in correctly designing and debugging their ontologies. Errors such as unsatisable concepts and inconsistent ontologies frequently occur during ontology construction. Ontology Debugging and Repair is concerned with helping the ontology developer to eliminate these errors from the ontology. Much emphasis, in current tools, has been placed on giving explanations as to why these errors occur in the ontology. Less emphasis has been placed on using this information to suggest ecient ways to eliminate the errors. Furthermore, these tools focus mainly on the errors of unsatisable concepts and inconsistent ontologies. In this dissertation we ll an important gap in the area by contributing an alternative approach to ontology debugging and repair for the more general error of a list of unwanted sentences. Errors such as unsatisable concepts and inconsistent ontologies can be represented as unwanted sentences in the ontology. Our approach not only considers the explanation of the unwanted sentences but also the identication of repair strategies to eliminate these unwanted sentences from the ontology.

@phdthesis{33,
  author = {Kody Moodley},
  title = {Debugging and Repair of Description Logic Ontologies},
  abstract = {In logic-based Knowledge Representation and Reasoning (KRR), ontologies are used to
represent knowledge about a particular domain of interest in a precise way. The building
blocks of ontologies include concepts, relations and objects. Those can be combined to
form logical sentences which explicitly describe the domain. With this explicit knowledge
one can perform reasoning to derive knowledge that is implicit in the ontology. Description
Logics (DLs) are a group of knowledge representation languages with such capabilities that
are suitable to represent ontologies. The process of building ontologies has been greatly
simplied with the advent of graphical ontology editors such as SWOOP, Protege and
OntoStudio. The result of this is that there are a growing number of ontology engineers
attempting to build and develop ontologies. It is frequently the case that errors are
introduced while constructing the ontology resulting in undesirable pieces of implicit
knowledge that follows from the ontology. As such there is a need to extend current
ontology editors with tool support to aid these ontology engineers in correctly designing
and debugging their ontologies. Errors such as unsatisable concepts and inconsistent
ontologies frequently occur during ontology construction. Ontology Debugging and Repair
is concerned with helping the ontology developer to eliminate these errors from the ontology.
Much emphasis, in current tools, has been placed on giving explanations as to why these
errors occur in the ontology. Less emphasis has been placed on using this information to
suggest ecient ways to eliminate the errors. Furthermore, these tools focus mainly on the
errors of unsatisable concepts and inconsistent ontologies. In this dissertation we ll an
important gap in the area by contributing an alternative approach to ontology debugging
and repair for the more general error of a list of unwanted sentences. Errors such as
unsatisable concepts and inconsistent ontologies can be represented as unwanted sentences
in the ontology. Our approach not only considers the explanation of the unwanted sentences
but also the identication of repair strategies to eliminate these unwanted sentences from
the ontology.},
  year = {2011},
  volume = {MSc},
  url = {http://ksg.meraka.org.za/~kmoodley/MSc%20Dissertation%20-%20KMoodley.pdf},
}

No Abstract

@{32,
  author = {Kody Moodley and Tommie Meyer and Ivan Varzinczak},
  title = {Root Justifications for Ontology Repair},
  abstract = {No Abstract},
  year = {2011},
  journal = {Fifth International Conference on Web Reasoning and Rule Systems},
  pages = {275-280},
}

We introduce an algorithm for MinA extraction in EL based on bidirectional reachability. We obtain a significant reduction in the size of modules extracted at almost no additional cost to that of extracting standard reachability-based modules. Bidirectional modules are related to nested locality modules, but are aimed specifically at MinA extraction and are generally smaller. For acyclic EL TBoxes consisting of only primitive concept inclusions, all MinAs can be extracted without the need for subsumption testing.

@misc{30,
  author = {Riku Nortjé and Katarina Britz and Tommie Meyer},
  title = {Bidirectional reachability-based modules},
  abstract = {We introduce an algorithm for MinA extraction in EL based on bidirectional reachability. We obtain a significant reduction in the size of modules extracted at almost no additional cost to that of extracting standard reachability-based modules. Bidirectional modules are related to nested locality modules, but are aimed specifically at MinA extraction and are generally smaller. For acyclic EL TBoxes consisting of only primitive concept inclusions, all MinAs can be extracted without the need for subsumption testing.},
  year = {2011},
  journal = {24th International Workshop on Description Logics (DL 2011)},
  month = {13/07 - 16/07},
}

No Abstract

@article{29,
  author = {Ken Halland and Katarina Britz and Aurona Gerber},
  title = {Investigations into the use of SNOMED CT to enhance an Open-MRS health information system},
  abstract = {No Abstract},
  year = {2011},
  journal = {South African Computer Journal},
  volume = {47},
  pages = {33-46},
}

The preferential and rational consequence relations first studied by Lehmann and colleagues play a central role in non-monotonic reasoning, not least because they provide the foundation for the determination of the important notion of rational closure. Although they can be applied directly to a large variety of logics, these constructions suffer from the limitation that they are largely propositional in nature. One of the main obstacles in moving beyond the propositional case has been the lack of a formal semantics which appropriately generalizes the preferential and ranked models of Lehmann et al. In this paper we propose a semantics to fill that gap for description logics, an important class of decidable fragments of first-order logic. Our semantics replaces the propositional valuations used in the models of Lehmann et al. with structures we refer to as concept models. We prove representation results for the description logic ALC for both preferential and rational consequence relations. We argue that our semantics paves the way for extending preferential and rational consequence, and therefore also rational closure, to a whole class of logics that have a semantics defined in terms of first-order relational structures.

@misc{28,
  author = {Katarina Britz and Tommie Meyer and Ivan Varzinczak},
  title = {Concept Model Semantics for DL Preferential Reasoning},
  abstract = {The preferential and rational consequence relations first studied by Lehmann and colleagues play a central role in non-monotonic reasoning, not least because they provide the foundation for the determination of the important notion of rational closure. Although they can be applied directly to a large variety of logics, these constructions suffer from the limitation that they are largely propositional in nature. One of the main obstacles in moving beyond the propositional case has been the lack of a formal semantics which appropriately generalizes the preferential and ranked models of Lehmann et al. In this paper we propose a semantics to fill that gap for description logics, an important class of decidable fragments of first-order logic. Our semantics replaces the propositional valuations used in the models of Lehmann et al. with structures we refer to as concept models. We prove representation results for the description logic ALC for both preferential and rational consequence relations. We argue that our semantics paves the way for extending preferential and rational consequence, and therefore also rational closure, to a whole class of logics that have a semantics defined in terms of first-order relational structures.},
  year = {2011},
  journal = {24th International Workshop on Description Logics (DL 2011)},
  month = {13/07 - 16/07},
}

Description logics are a well-established family of knowledge representation formalisms in Artificial Intelligence. Enriching description logics with non-monotonic reasoning capabilities, especially preferential reasoning as developed by Lehmann and colleagues in the 90's, would therefore constitute a natural extension of such KR formalisms. Nevertheless, there is at present no generally accepted semantics, with corresponding syntactic characterization, for preferential consequence in description logics. In this paper we fill this gap by providing a natural and intuitive semantics for defeasible subsumption in the description logic ALC. Our semantics replaces the propositional valuations used in the models of Lehmann et al. with structures we refer to as concept models. We present representation results for the description logic ALC for both preferential and rational consequence relations. We argue that our semantics paves the way for extending preferential and rational consequence, and therefore also rational closure, to a whole class of logics that have a semantics defined in terms of first-order relational structures.

@{27,
  author = {Katarina Britz and Tommie Meyer and Ivan Varzinczak},
  title = {Semantic Foundation for Preferential Description Logics},
  abstract = {Description logics are a well-established family of knowledge representation formalisms in Artificial Intelligence. Enriching description logics with non-monotonic reasoning capabilities, especially preferential reasoning as developed by Lehmann and colleagues in the 90's, would therefore constitute a natural extension of such KR formalisms. Nevertheless, there is at present no generally accepted semantics, with corresponding syntactic characterization, for preferential consequence in description logics. In this paper we fill this gap by providing a natural and intuitive semantics for defeasible subsumption in the description logic ALC. Our semantics replaces the propositional valuations used in the models of Lehmann et al. with structures we refer to as concept models. We present representation results for the description logic ALC for both preferential and rational consequence relations. We argue that our semantics paves the way for extending preferential and rational consequence, and therefore also rational closure, to a whole class of logics that have a semantics defined in terms of first-order relational structures.},
  year = {2011},
  journal = {Proceedings of the 24th Australasian Joint Conference on Artificial Intelligence},
  pages = {491-500},
}

We investigate the problem of maintaining and reasoning with different configurations of a logic-based agent. Given specific contexts, there may be several possible usual configurations that the agent's knowledge base can be in, and that one may want to access at different times. This can happen due to foreseeable exceptional situations one has to cater for, or different environments in which the agent may have to operate, or simply due to upgrades of the agent's initial configuration. In all these cases, there is a need for a system capable of managing possibly conflicting versions of the knowledge base and allowing the agent to switch between any two given configurations at run time. Building on Franconi et al.'s framework for propositional knowledge base versioning, here we establish the logical foundations for a general semantic-based architecture of such a system. Central to our approach is the notion of logical difference, which allows us to determine the essential pieces of information on which two given configurations of an agent differ.

@{26,
  author = {Tommie Meyer and Ivan Varzinczak},
  title = {A Logic-Based Perspective on Agent Reconfiguration: Preliminary Report},
  abstract = {We investigate the problem of maintaining and reasoning with different configurations of a logic-based agent. Given specific contexts, there may be several possible usual configurations that the agent's knowledge base can be in, and that one may want to access at different times. This can happen due to foreseeable exceptional situations one has to cater for, or different environments in which the agent may have to operate, or simply due to upgrades of the agent's initial configuration. In all these cases, there is a need for a system capable of managing possibly conflicting versions of the knowledge base and allowing the agent to switch between any two given configurations at run time. Building on Franconi et al.'s framework for propositional knowledge base versioning, here we establish the logical foundations for a general semantic-based architecture of such a system. Central to our approach is the notion of logical difference, which allows us to determine the essential pieces of information on which two given configurations of an agent differ.},
  year = {2011},
  journal = {IEEE Africon},
}

There are various contexts in which it is not pertinent to generate and attend to all the classical consequences of a given premiss—or to trace all the premisses which classically entail a given consequence. Such contexts may involve limited resources of an agent or inferential engine, contextual relevance or irrelevance of certain consequences or premisses, modelling everyday human reasoning, the search for plausible abduced hypotheses or potential causes, etc. In this paper we propose and expli- cate one formal framework for a whole spectrum of consequence relations, flexible enough to be tailored for choices from a variety of contexts. We do so by investigating semantic constraints on classical entailment which give rise to a family of infra-classical logics with appealing properties. More specifically, our infra-classical reasoning demands (beyond α |= β) that Mod(β) does not run wild, but lies within the scope (whatever that may mean in some specific context) of Mod(α), and which can be described by a sentence •α with β |= •α. Besides being infra-classical, the resulting logic is also non-monotonic and allows for non-trivial reasoning in the presence of inconsistencies.

@article{25,
  author = {Katarina Britz and J. Heidema and Ivan Varzinczak},
  title = {Constrained Consequence},
  abstract = {There are various contexts in which it is not pertinent to generate and attend to all the classical consequences of a given premiss—or to trace all the premisses which classically entail a given consequence. Such contexts may involve limited resources of an agent or inferential engine, contextual relevance or irrelevance of certain consequences or premisses, modelling everyday human reasoning, the search for plausible abduced hypotheses or potential causes, etc. In this paper we propose and expli- cate one formal framework for a whole spectrum of consequence relations, flexible enough to be tailored for choices from a variety of contexts. We do so by investigating semantic constraints on classical entailment which give rise to a family of infra-classical logics with appealing properties. More specifically, our infra-classical reasoning demands (beyond α |= β) that Mod(β) does not run wild, but lies within the scope (whatever that may mean in some specific context) of Mod(α), and which can be described by a sentence •α with β |= •α. Besides being infra-classical, the resulting logic is also non-monotonic and allows for non-trivial reasoning in the presence of inconsistencies.},
  year = {2011},
  journal = {Logica Universalis},
  volume = {5},
  pages = {327-350},
  issue = {2},
}

Standard belief change assumes an underlying logic containing full classical propositional logic. However, there are good reasons for considering belief change in less expressive logics as well. In this paper we build on recent investigations by Delgrande on contraction for Horn logic. We show that the standard basic form of contraction, partial meet, is too strong in the Horn case. This result stands in contrast to Delgrande's conjecture that orderly maxichoice is the appropriate form of contraction for Horn logic. We then define a more appropriate notion of basic contraction for the Horn case, influenced by the convexity property holding for full propositional logic and which we refer to as infra contraction. The main contribution of this work is a result which shows that the construction method for Horn contraction for belief sets based on our infra remainder sets corresponds exactly to Hansson's classical kernel contraction for belief sets, when restricted to Horn logic. This result is obtained via a detour through contraction for belief bases. We prove that kernel contraction for belief bases produces precisely the same results as the belief base version of infra contraction. The use of belief bases to obtain this result provides evidence for the conjecture that Horn belief change is best viewed as a 'hybrid' version of belief set change and belief base change. One of the consequences of the link with base contraction is the provision of a representation result for Horn contraction for belief sets in which a version of the Core-retainment postulate features.

@article{24,
  author = {Richard Booth and Tommie Meyer and Ivan Varzinczak and R. Wassermann},
  title = {On the Link between Partial Meet, Kernel, and Infra Contraction and its Application to Horn Logic},
  abstract = {Standard belief change assumes an underlying logic containing full classical propositional logic. However, there are good reasons for considering belief change in less expressive logics as well. In this paper we build on recent investigations by Delgrande on contraction for Horn logic. We show that the standard basic form of contraction, partial meet, is too strong in the Horn case. This result stands in contrast to Delgrande's conjecture that orderly maxichoice is the appropriate form of contraction for Horn logic. We then define a more appropriate notion of basic contraction for the Horn case, influenced by the convexity property holding for full propositional logic and which we refer to as infra contraction. The main contribution of this work is a result which shows that the construction method for Horn contraction for belief sets based on our infra remainder sets corresponds exactly to Hansson's classical kernel contraction for belief sets, when restricted to Horn logic. This result is obtained via a detour through contraction for belief bases. We prove that kernel contraction for belief bases produces precisely the same results as the belief base version of infra contraction. The use of belief bases to obtain this result provides evidence for the conjecture that Horn belief change is best viewed as a 'hybrid' version of belief set change and belief base change. One of the consequences of the link with base contraction is the provision of a representation result for Horn contraction for belief sets in which a version of the Core-retainment postulate features.},
  year = {2011},
  journal = {Journal of Artificial Intelligence Research},
  volume = {42},
  pages = {31-53},
}

Modal logic is the foundation for a versatile and well-established class of knowledge representation formalisms in artificial intelligence. Enriching modal logics with non-monotonic reasoning capabilities such as preferential reasoning as developed by Lehmann and colleagues would therefore constitute a natural extension of such KR formalisms. Nevertheless, there is at present no generally accepted semantics, with corresponding syntactic characterization, for preferential consequence in modal logics. In this paper we fill this gap by providing a natural and intuitive semantics for preferential and rational modal consequence. We do so by placing a preference order on possible worlds indexed by Kripke models they belong to. We also prove representation results for both preferential and rational consequence, which paves the way for effective decision procedures for modal preferential reasoning. We then illustrate applications of our constructions to modal logics widely used in AI, notably in the contexts of reasoning about actions, knowledge and beliefs. We argue that our semantics constitutes the foundation on which to explore preferential reasoning in modal logics in general.

@article{23,
  author = {Katarina Britz and Tommie Meyer and Ivan Varzinczak},
  title = {Preferential Reasoning for Modal Logic},
  abstract = {Modal logic is the foundation for a versatile and well-established class of knowledge representation formalisms in artificial intelligence. Enriching modal logics with non-monotonic reasoning capabilities such as preferential reasoning as developed by Lehmann and colleagues would therefore constitute a natural extension of such KR formalisms. Nevertheless, there is at present no generally accepted semantics, with corresponding syntactic characterization, for preferential consequence in modal logics. In this paper we fill this gap by providing a natural and intuitive semantics for preferential and rational modal consequence. We do so by placing a preference order on possible worlds indexed by Kripke models they belong to. We also prove representation results for both preferential and rational consequence, which paves the way for effective decision procedures for modal preferential reasoning. We then illustrate applications of our constructions to modal logics widely used in AI, notably in the contexts of reasoning about actions, knowledge and beliefs. We argue that our semantics constitutes the foundation on which to explore preferential reasoning in modal logics in general.},
  year = {2011},
  journal = {Electronic Notes in Theoretical Computer Science},
  volume = {278},
  pages = {55-69},
}