Research Publications

2011

Meyer T, Varzinczak I. A Logic-Based Perspective on Agent Reconfiguration: Preliminary Report. In: IEEE Africon. ; 2011.

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 = {Thomas 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},
}
Britz K, Heidema J, Varzinczak I. Constrained Consequence. Logica Universalis. 2011;5(2).

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},
}
Booth R, Meyer T, Varzinczak I, Wassermann R. On the Link between Partial Meet, Kernel, and Infra Contraction and its Application to Horn Logic. Journal of Artificial Intelligence Research. 2011;42.

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 Thomas 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},
}
Britz K, Meyer T, Varzinczak I. Preferential Reasoning for Modal Logic. Electronic Notes in Theoretical Computer Science. 2011;278.

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 Thomas 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},
}
Booth R, Meyer T. Belief Change. In: Logic and Philosophy Today, Vol. 1, Studies in Logic, Vol. 29. College Publications; 2011. www.collegepublications.co.uk/logic/mlf/?00017.

In this paper we present a brief overview of belief change, a research area concerned with the question of how a rational agent ought to change its mind in the face of new, possibly conflicting, information. We limit ourselves to logic-based belief change, with a particular emphasis on classical propositional logic as the underlying logic in which beliefs are to be represented. Our intention is to provide the reader with a basic introduction to the work done in this area over the past 30 years. In doing so we hope to sketch the main historical results, provide appropriate pointers to further references, and discuss some current developments. We trust that this will spur on the interested reader to learn more about the topic, and perhaps to join us in the further development of this exciting field of research.

@inbook{17,
  author = {Richard Booth and Thomas Meyer},
  title = {Belief Change},
  abstract = {In this paper we present a brief overview of belief change, a research area concerned with the question of how a rational agent ought to change its mind in the face of new, possibly conflicting, information. We limit ourselves to logic-based belief change, with a particular emphasis on classical propositional logic as the underlying logic in which beliefs are to be represented. Our intention is to provide the reader with a basic introduction to the work done in this area over the past 30 years. In doing so we hope to sketch the main historical results, provide appropriate pointers to further references, and discuss some current developments. We trust that this will spur on the interested reader to learn more about the topic, and perhaps to join us in the further development of this exciting field of research.},
  year = {2011},
  journal = {Logic and Philosophy Today, Vol. 1, Studies in Logic, Vol. 29},
  pages = {385-422},
  publisher = {College Publications},
  url = {www.collegepublications.co.uk/logic/mlf/?00017},
}
Hajek M, Singh Y. Medical AI - HIV/AIDS Treatment Management System. In: Beyond AI: Interdisciplinary Aspects of Artificial Intelligence. ; 2011.

Medical AI has established itself as a robust and fruitful field in the last 30 years. Most resource poor countries face the triple burden of malaria, tuberculosis and HIV. This coupled with the problems of lack of infrastructure, scarcity of clinical staff, and complex clinical guidelines, have encouraged the application of AI in healthcare specifially on practical issues of field medical data collection, mining, and better integration with healthcare workfow. One such application is an HIV/AIDS antiretroviral therapy management system that uses AI algorithm to predict drug resistance and the progression of the disease. Another serious problem is the scarcity of personnel with sucient AI knowledge in the medical field. A distance education has shown its potential to remedy the problem.

@{15,
  author = {Milan Hajek and Y. Singh},
  title = {Medical AI - HIV/AIDS Treatment Management System},
  abstract = {Medical AI has established itself as a robust and fruitful field in the last 30 years. Most resource poor countries face the triple burden of malaria, tuberculosis and HIV. This coupled with the problems of lack of infrastructure, scarcity of clinical staff, and complex clinical guidelines, have encouraged the application of AI in healthcare specifially on practical issues of field medical data collection, mining, and better integration with healthcare workfow. One such application is an HIV/AIDS antiretroviral therapy management system that uses AI algorithm to predict drug resistance and the progression of the disease. Another serious problem is the scarcity of personnel with sucient AI knowledge in the medical field. A distance education has shown its potential to remedy the problem.},
  year = {2011},
  journal = {Beyond AI: Interdisciplinary Aspects of Artificial Intelligence},
}
Gous H, Gard J, Gerber A. Business architecture for inter-organisational innovation networks: A case study comparison from South Africa and Germany. In: ICE 2011. ; 2011.

The range of inter-organisational innovation networks existing in the global economy today show a wide variance in structure, purpose, location, lifespan and maturity. These differences between network instantiations highlight the need for deeper understanding of the operation of these networks in order to enable efforts to improve network performance. These efforts include strategic management routines for network leadership, as well as the development of appropriate support structures, e.g. information systems architectures. An important step towards a deeper understanding of inter-organisational innovation networks is to compare the business architectures of network case studies to identify similarities and differences in terms of scope and context, business concepts and underlying system logic. The Zachman framework for enterprise architecture provides an approach to structuring the business architecture of enterprises in a way that allows such comparisons to be drawn. This paper describes the business architecture of two contrasting network case studies from South Africa and Germany within the Zachman framework, and draws some conclusions based on the observed similarities and conclusions.

@{14,
  author = {Henno Gous and J. Gard and Aurona Gerber},
  title = {Business architecture for inter-organisational innovation networks:  A case study comparison from South Africa and Germany},
  abstract = {The range of inter-organisational innovation networks existing in the global economy today show a wide variance in structure, purpose, location, lifespan and maturity. These differences between network instantiations highlight the need for deeper understanding of the operation of these networks in order to enable efforts to improve network performance. These efforts include strategic management routines for network leadership, as well as the development of appropriate support structures, e.g. information systems architectures.
An important step towards a deeper understanding of inter-organisational innovation networks is to compare the business architectures of network case studies to identify similarities and differences in terms of scope and context, business concepts and underlying system logic. The Zachman framework for enterprise architecture provides an approach to structuring the business architecture of enterprises in a way that allows such comparisons to be drawn. This paper describes the business architecture of two contrasting network case studies from South Africa and Germany within the Zachman framework, and draws some conclusions based on the observed similarities and conclusions.},
  year = {2011},
  journal = {ICE 2011},
}
Moodley D, Tapamo JR. A semantic infrastructure for a Knowledge Driven Sensor Web. In: Proceedings of the 4th International Workshop on Semantic Sensor Networks 2011 (SSN11), 23 October 2011,Bonn, Germany, A workshop of the 10th International Semantic Web Conference (ISWC 2011). ; 2011.

No Abstract

@{9,
  author = {Deshen Moodley and J. Tapamo},
  title = {A semantic infrastructure for a Knowledge Driven Sensor Web},
  abstract = {No Abstract},
  year = {2011},
  journal = {Proceedings of the 4th International Workshop on Semantic Sensor Networks 2011 (SSN11), 23 October 2011,Bonn, Germany,  A workshop of the 10th International Semantic Web Conference (ISWC 2011)},
}
  • CSIR
  • DSI
  • Covid-19