title: The online performance estimation framework: heterogeneous ensemble learning for data streams

authors: van Rijn, Jan N.

subjects: Science & Technology

abstract: Ensembles of classifiers are among the best performing classifiers available in many data mining applications, including the mining of data streams. Rather than training one classifier, multiple classifiers are trained, and their predictions are combined according to a given voting schedule. An important prerequisite for ensembles to be successful is that the individual models are diverse. One way to vastly increase the diversity among the models is to build an heterogeneous ensemble, comprised of fundamentally different model types. However, most ensembles developed specifically for the dynamic data stream setting rely on only one type of base-level classifier, most often Hoeffding Trees. We study the use of heterogeneous ensembles for data streams. We introduce the Online Performance Estimation framework, which dynamically weights the votes of individual classifiers in an ensemble. Using an internal evaluation on recent training data, it measures how well ensemble members performed on this and dynamically updates their weights. Experiments over a wide range of data streams show performance that is competitive with state of the art ensemble techniques, including Online Bagging and Leveraging Bagging, while being significantly faster. All experimental results from this work are easily reproducible and publicly available online.

text: The online performance estimation framework: heterogeneous ensemble learning for data streams Ensembles of classifiers are among the best performing classifiers available in many data mining applications, including the mining of data streams. Rather than training one classifier, multiple classifiers are trained, and their predictions are combined according to a given voting schedule. An important prerequisite for ensembles to be successful is that the individual models are diverse. One way to vastly increase the diversity among the models is to build an heterogeneous ensemble, comprised of fundamentally different model types. However, most ensembles developed specifically for the dynamic data stream setting rely on only one type of base-level classifier, most often Hoeffding Trees. We study the use of heterogeneous ensembles for data streams. We introduce the Online Performance Estimation framework, which dynamically weights the votes of individual classifiers in an ensemble. Using an internal evaluation on recent training data, it measures how well ensemble members performed on this and dynamically updates their weights. Experiments over a wide range of data streams show performance that is competitive with state of the art ensemble techniques, including Online Bagging and Leveraging Bagging, while being significantly faster. All experimental results from this work are easily reproducible and publicly available online.

year: 2018

title: Semigroups with if-then-else and halting programs

authors: Jackson, Marcel

subjects: transformation

abstract: The "if–then–else" construction is one of the most elementary programming commands, and its abstract laws have been widely studied, starting with McCarthy. Possibly, the most obvious extension of this is to include the operation of composition of programs, which gives a semigroup of functions (total, partial, or possibly general binary relations) that can be recombined using if–then–else. We show that this particular extension admits no finite complete axiomatization and instead focus on the case where composition of functions with predicates is also allowed (and we argue there is good reason to take this approach). In the case of total functions — modeling halting programs — we give a complete axiomatization for the theory in terms of a finite system of equations. We obtain a similar result when an operation of equality test and/or fixed point test is included.

text: Semigroups with if-then-else and halting programs The "if–then–else" construction is one of the most elementary programming commands, and its abstract laws have been widely studied, starting with McCarthy. Possibly, the most obvious extension of this is to include the operation of composition of programs, which gives a semigroup of functions (total, partial, or possibly general binary relations) that can be recombined using if–then–else. We show that this particular extension admits no finite complete axiomatization and instead focus on the case where composition of functions with predicates is also allowed (and we argue there is good reason to take this approach). In the case of total functions — modeling halting programs — we give a complete axiomatization for the theory in terms of a finite system of equations. We obtain a similar result when an operation of equality test and/or fixed point test is included.

year: 2009

title: Urban Māori Whānau Connection / Re Connection to Cultural Confidence Via Wānanga

authors: Maihi, Bonnie

abstract: The  purpose  of this research is to explore and interrogate  dynamics  involved  with positive health and transformation of urban Māori whānau and the challenges of pursuing this using the medium of wānanga. The research component of this thesis rest around a recent series of whānau wānanga held and embarked on in partnership with my whānau through a journey of re-connecting back to our whakapapa, marae and our culture. Current statistics for Māori reflect health and well-being as a site of continuous struggle and one where much work is necessary to ensure equitable outcomes for Māori. While equitable outcomes are an ‘in the future’ dream what remains is asking what steps do we have to take as a whānau? What is the Māori culture that we must capture, know, and strive for, in our whānau journey of self-discovery?

The theoretical framework guiding this thesis is that of Kaupapa Māori. Within Kaupapa Māori theory acknowledgement and recognition of the effects of colonisation, destruction of culture and power 
imbalances are known as a given, with no need to question the validity of whether or not these are true accounts. A comprehensive literature review covering wānanga, Māori culture, Māori health &  well-being, sustainability and more is included in this study. In terms of the research component, five significant themes have been sourced from a series of semi-structured interviews to best represent the experiences of my whānau members pertaining to connection to whakapapa; te reo Māori; tikanga Māori and marae. They are as follows: structural inequality; influences on Māori identity; cultural confidence; whānau capacities; and resistive strategies.

Results identified spaces of progress and spaces that needed strengthening in relation to whānau building cultural confidence and connection to a Māori identity. In conclusion, this thesis ascertains a need for whānau to foster appreciation for lifelong learning and a compassionate approach for those teaching as key markers for nurturing and reconnecting urban Māori whānau to their cultural roots.

text: Urban Māori Whānau Connection / Re Connection to Cultural Confidence Via Wānanga The  purpose  of this research is to explore and interrogate  dynamics  involved  with positive health and transformation of urban Māori whānau and the challenges of pursuing this using the medium of wānanga. The research component of this thesis rest around a recent series of whānau wānanga held and embarked on in partnership with my whānau through a journey of re-connecting back to our whakapapa, marae and our culture. Current statistics for Māori reflect health and well-being as a site of continuous struggle and one where much work is necessary to ensure equitable outcomes for Māori. While equitable outcomes are an ‘in the future’ dream what remains is asking what steps do we have to take as a whānau? What is the Māori culture that we must capture, know, and strive for, in our whānau journey of self-discovery?

The theoretical framework guiding this thesis is that of Kaupapa Māori. Within Kaupapa Māori theory acknowledgement and recognition of the effects of colonisation, destruction of culture and power 
imbalances are known as a given, with no need to question the validity of whether or not these are true accounts. A comprehensive literature review covering wānanga, Māori culture, Māori health &  well-being, sustainability and more is included in this study. In terms of the research component, five significant themes have been sourced from a series of semi-structured interviews to best represent the experiences of my whānau members pertaining to connection to whakapapa; te reo Māori; tikanga Māori and marae. They are as follows: structural inequality; influences on Māori identity; cultural confidence; whānau capacities; and resistive strategies.

Results identified spaces of progress and spaces that needed strengthening in relation to whānau building cultural confidence and connection to a Māori identity. In conclusion, this thesis ascertains a need for whānau to foster appreciation for lifelong learning and a compassionate approach for those teaching as key markers for nurturing and reconnecting urban Māori whānau to their cultural roots.

year: 2016