title: Tie-breaking in Hoeffding trees

authors: Holmes, Geoffrey

subjects: computer science

abstract: A thorough examination of the performance of Hoeffding trees, state-of-the-art in classification for data streams, on a range of datasets reveals that tie breaking, an essential but supposedly rare procedure, is employed much more than expected. Testing with a lightweight method for handling continuous attributes, we find that the excessive invocation of tie breaking causes performance to degrade significantly on complex and noisy data. Investigating ways to reduce the number of tie breaks, we propose an adaptive method that overcomes the problem while not significantly affecting performance on simpler datasets.

text: Tie-breaking in Hoeffding trees A thorough examination of the performance of Hoeffding trees, state-of-the-art in classification for data streams, on a range of datasets reveals that tie breaking, an essential but supposedly rare procedure, is employed much more than expected. Testing with a lightweight method for handling continuous attributes, we find that the excessive invocation of tie breaking causes performance to degrade significantly on complex and noisy data. Investigating ways to reduce the number of tie breaks, we propose an adaptive method that overcomes the problem while not significantly affecting performance on simpler datasets.

year: 2005

title: Modelling sustainable ecotourism development on the Coromandel Peninsula in Aotearoa / New Zealand; a holistic systems approach based on the idea of chaos and complexity in a human-activity system

authors: Holzapfel, Rupert

abstract: This thesis studies ecotourism in the context of sustainable tourism development. The research is based on the premise that ecotourism and sustainable development can be expressed as operational theoretical concepts and as fields of empirical inquiry. Positioned in the realm of applied qualitative research in the social sciences, the study’s leitmotiv is that sustainable ecotourism development can be represented from an integrative perspective by designing a conceptual system model. The field work consists of an empirical inquiry placed in the Coromandel Peninsula in New Zealand/Aotearoa. By employing a regional case study to test the hypotheses of the thesis, the research attains an insight in the operationalisation of ecotourism and sustainable ecotourism development. It further produces new knowledge regarding the theorisation and conceptualisation of ecotourism and sustainable tourism development. 

Two main goals drive the study. The first is the exploration of the ontological, epistemological and ideological matrix of a holistic and systemic research perspective. The second goal is the examination of the methodological and practical utility of conceptual system modelling as a research approach. The adopted strategy allows for causal, correlative and teleological interpretations of the spatio-temporal physical and mental phenomena encountered.

With reference to critical realism the modelling process is recognised as an abstraction of ‘actual reality’ as opposed to ‘real reality’. Critical realism as an ontology accounts for the different ‘situated knowledges’ and worldviews that are present in the Coromandel Peninsula. The model itself reflects the researcher’s perception of an ‘empirical reality’, which is depicted at three resolution levels. Progressively coupling the different scales, the model design focuses on: (1) The configuration and behavioural patterns of the system as a whole; (2) the attributes of nested subsystems and their influences on each other as well as on the whole system; (3) the properties of individual system constituents, the processes and relationships linking these elements, and their effects on subsets of the system as well as on the system as a whole. Structural and process analyses, as well as an aetiological account of the system’s variables, do justice to the experienced complexity.

At each resolution level the research outcome entails two simultaneously developed models. Both show the characteristics of open, complex and adaptive human-activity systems. While the first model reflects the status quo of sustainable ecotourism development in the Coromandel Peninsula, the second one represents an idealised archetype that can be used as a grid for further improvements. Neither model offers a fait accompli. Having identified ecotourism and sustainable tourism development as subjective and dynamic problem areas, answers exist within a continuum of differential interpretations, satisfying changing interests, needs and expectations. Solutions are thus of a suggestive and tentative nature. 
On a theoretical level, the study utilises ideas derived from ‘general system theory’ and the ‘chaoplexity paradigm’. Conceptually, it expands the philosophical notion of methodological holism into a pluralistic approach. Methodological triangulation is employed to compensate for the anticipated shortcomings of individual methods. In a pragmatic sense ecotourism and sustainable tourism development are viewed as anthropogenic phenomena that emerge at the interface between humans and the natural environment. Human agency is interpreted as the fulcrum of the system’s evolution, which operates in both the mental and physical dimension.

Assuming that humans possess ‘free will’, and that rational and irrational as well as emotive and intuitive behaviour are inherent faculties of our nature, the system’s dynamics can not be sufficiently described via linear causalities. Non-linear relations, and a complex combination of multivariate and contingent causation, are interpreted predominantly as a result of human encounter and interaction. Answers to what should be ‘right’ and ‘wrong’ in ecotourism practice are based on the adoption of a pluralistic moral stance. This approach allows for competitive as well as cooperative elements as inherent human character traits that drive decision-making processes.

Based on the findings, the thesis concludes with a flexible template of systemic indices that can evaluate the environmental performance and development of ecotourism. It is argued that utilising the suggested set of complex indicators in conjunction bears the potential to enhance sustainable ecotourism development. The template’s adaptability to specific situational contexts is viewed as a prerequisite to cater for changing demands and expectations of individuals, local communities and regions.

text: Modelling sustainable ecotourism development on the Coromandel Peninsula in Aotearoa / New Zealand; a holistic systems approach based on the idea of chaos and complexity in a human-activity system This thesis studies ecotourism in the context of sustainable tourism development. The research is based on the premise that ecotourism and sustainable development can be expressed as operational theoretical concepts and as fields of empirical inquiry. Positioned in the realm of applied qualitative research in the social sciences, the study’s leitmotiv is that sustainable ecotourism development can be represented from an integrative perspective by designing a conceptual system model. The field work consists of an empirical inquiry placed in the Coromandel Peninsula in New Zealand/Aotearoa. By employing a regional case study to test the hypotheses of the thesis, the research attains an insight in the operationalisation of ecotourism and sustainable ecotourism development. It further produces new knowledge regarding the theorisation and conceptualisation of ecotourism and sustainable tourism development. 

Two main goals drive the study. The first is the exploration of the ontological, epistemological and ideological matrix of a holistic and systemic research perspective. The second goal is the examination of the methodological and practical utility of conceptual system modelling as a research approach. The adopted strategy allows for causal, correlative and teleological interpretations of the spatio-temporal physical and mental phenomena encountered.

With reference to critical realism the modelling process is recognised as an abstraction of ‘actual reality’ as opposed to ‘real reality’. Critical realism as an ontology accounts for the different ‘situated knowledges’ and worldviews that are present in the Coromandel Peninsula. The model itself reflects the researcher’s perception of an ‘empirical reality’, which is depicted at three resolution levels. Progressively coupling the different scales, the model design focuses on: (1) The configuration and behavioural patterns of the system as a whole; (2) the attributes of nested subsystems and their influences on each other as well as on the whole system; (3) the properties of individual system constituents, the processes and relationships linking these elements, and their effects on subsets of the system as well as on the system as a whole. Structural and process analyses, as well as an aetiological account of the system’s variables, do justice to the experienced complexity.

At each resolution level the research outcome entails two simultaneously developed models. Both show the characteristics of open, complex and adaptive human-activity systems. While the first model reflects the status quo of sustainable ecotourism development in the Coromandel Peninsula, the second one represents an idealised archetype that can be used as a grid for further improvements. Neither model offers a fait accompli. Having identified ecotourism and sustainable tourism development as subjective and dynamic problem areas, answers exist within a continuum of differential interpretations, satisfying changing interests, needs and expectations. Solutions are thus of a suggestive and tentative nature. 
On a theoretical level, the study utilises ideas derived from ‘general system theory’ and the ‘chaoplexity paradigm’. Conceptually, it expands the philosophical notion of methodological holism into a pluralistic approach. Methodological triangulation is employed to compensate for the anticipated shortcomings of individual methods. In a pragmatic sense ecotourism and sustainable tourism development are viewed as anthropogenic phenomena that emerge at the interface between humans and the natural environment. Human agency is interpreted as the fulcrum of the system’s evolution, which operates in both the mental and physical dimension.

Assuming that humans possess ‘free will’, and that rational and irrational as well as emotive and intuitive behaviour are inherent faculties of our nature, the system’s dynamics can not be sufficiently described via linear causalities. Non-linear relations, and a complex combination of multivariate and contingent causation, are interpreted predominantly as a result of human encounter and interaction. Answers to what should be ‘right’ and ‘wrong’ in ecotourism practice are based on the adoption of a pluralistic moral stance. This approach allows for competitive as well as cooperative elements as inherent human character traits that drive decision-making processes.

Based on the findings, the thesis concludes with a flexible template of systemic indices that can evaluate the environmental performance and development of ecotourism. It is argued that utilising the suggested set of complex indicators in conjunction bears the potential to enhance sustainable ecotourism development. The template’s adaptability to specific situational contexts is viewed as a prerequisite to cater for changing demands and expectations of individuals, local communities and regions.

year: 2003

title: The presence of the past: Maori history in contemporary reflection

authors: Mahuika, Nepia

abstract: This is the opening line of a famous saying in my tribe. For our people - Ngāti Porou - these words have become embedded in our tribal identity as important directives that we are encouraged to aspire to. In the “days destined to you”, Ngata reminds us that each generation has its own mana (or authority), our own responsibilities and challenges, our own dreams and destinies to fulfil, and our own histories to tell about Ngāti Porou: who we are, our past, present, and future. If we consider this expectant, and I think hopeful, affirmation as a gift and responsibility, then taking real ownership of the “days destined to us” requires us to know what our forebears have entrusted us with. What are those historical gifts that we might use to “centre” and assert ourselves as Māori, as Ngāti Porou? We might look at this directly, i mua: the past before us because it is our history that is so crucial to us as we walk consciously, and with determination, into the future. Our past before us helps us to know where we are going, it helps us correc our course when we stray, keeps us mindful of the “kaupapa”: whatever that might be in our generation and corner of the Maori universe. We’ve heard already today from both Enoka and Arini how Māori, in our own ways, are engaging with our past, drawing on our korero tuku iho (our oral histories passed down across the generations), on our whakairo (our carving), to illuminate the many ways Māori do, and think about, the past.

text: The presence of the past: Maori history in contemporary reflection This is the opening line of a famous saying in my tribe. For our people - Ngāti Porou - these words have become embedded in our tribal identity as important directives that we are encouraged to aspire to. In the “days destined to you”, Ngata reminds us that each generation has its own mana (or authority), our own responsibilities and challenges, our own dreams and destinies to fulfil, and our own histories to tell about Ngāti Porou: who we are, our past, present, and future. If we consider this expectant, and I think hopeful, affirmation as a gift and responsibility, then taking real ownership of the “days destined to us” requires us to know what our forebears have entrusted us with. What are those historical gifts that we might use to “centre” and assert ourselves as Māori, as Ngāti Porou? We might look at this directly, i mua: the past before us because it is our history that is so crucial to us as we walk consciously, and with determination, into the future. Our past before us helps us to know where we are going, it helps us correc our course when we stray, keeps us mindful of the “kaupapa”: whatever that might be in our generation and corner of the Maori universe. We’ve heard already today from both Enoka and Arini how Māori, in our own ways, are engaging with our past, drawing on our korero tuku iho (our oral histories passed down across the generations), on our whakairo (our carving), to illuminate the many ways Māori do, and think about, the past.

year: 2016