title: FEAT: A fairness-enhancing and concept-adapting decision tree classifier

authors: Zhang, Wenbin

subjects: computer science

abstract: Fairness-aware learning is increasingly important in socially-sensitive applications for the sake of achieving optimal and non-discriminative decision-making. Most of the proposed fairness-aware learning algorithms process the data in offline settings and assume that the data is generated by a single concept without drift. Unfortunately, in many real-world applications, data is generated in a streaming fashion and can only be scanned once. In addition, the underlying generation process might also change over time. In this paper, we propose and illustrate an efficient algorithm for mining fair decision trees from discriminatory and continuously evolving data streams. This algorithm, called FEAT (Fairness-Enhancing and concept-Adapting Tree), is based on using the change detector to learn adaptively from non-stationary data streams, that also accounts for fairness. We study FEAT’s properties and demonstrate its utility through experiments on a set of discriminated and time-changing data streams.

text: FEAT: A fairness-enhancing and concept-adapting decision tree classifier Fairness-aware learning is increasingly important in socially-sensitive applications for the sake of achieving optimal and non-discriminative decision-making. Most of the proposed fairness-aware learning algorithms process the data in offline settings and assume that the data is generated by a single concept without drift. Unfortunately, in many real-world applications, data is generated in a streaming fashion and can only be scanned once. In addition, the underlying generation process might also change over time. In this paper, we propose and illustrate an efficient algorithm for mining fair decision trees from discriminatory and continuously evolving data streams. This algorithm, called FEAT (Fairness-Enhancing and concept-Adapting Tree), is based on using the change detector to learn adaptively from non-stationary data streams, that also accounts for fairness. We study FEAT’s properties and demonstrate its utility through experiments on a set of discriminated and time-changing data streams.

year: 2020-10-15

title: Problematised History Pedagogy as Narrative Research: Self-Fashioning, Dismantled Voices and Reimaginings in History Education

authors: Hunter, Philippa Anne

subjects: history education

abstract: A growing disturbance with history’s identity in the New Zealand schooling curriculum disrupted my educational socialisation (curriculum, professional, academic) and inheritance of educational policy decisions. In turn, this disturbance shaped a critical stance in my research and practitioner work. Accordingly, problematised history pedagogy [PHP] emerged as the phenomenon and method of my doctoral study and was activated as a counterpoint to my experiences of normalised discourses of history curriculum and pedagogy. The PHP as narrative research was situated in my history curriculum programme in a postgraduate year of secondary teacher education. The research aimed to engage my history class (research participants as preservice teachers) in pedagogy that involved critique of and reflection on the things we do as history teachers in the secondary curriculum. The PHP was nested within my historicising and theorising of educational experience. Conceptualised as a reciprocal research process, the PHP involved the participants and me in theorising pedagogies, fashioning pedagogic identities, and engaging critically with curriculum conceptions of history. The PHP sought to reimagine history curriculum and pedagogy and identify pedagogic spaces of possibility. 

	The narrative research was layered as a bricolage of storying that reflected the interdisciplinary nature of my educational socialisation. Experiences as a teacher educator, curriculum and assessment developer and researcher, meant many voices, discourses, and theories were woven into the narrative. This complex conceptual work focused on understandings of narrative; policy, curriculum and pedagogy; critical pedagogy; history; history education, and notions of space. The narrative research was constructed in three parts. Firstly, my narrative selves and shifts to a critical pedagogy stance were historicised and theorised through an autobiographical approach. An original dimension of this storying has been the use of vignettes that illuminate the convergence of educational experience, theorising, and reimaginings as an aesthetic and critical narrative device. The second part of the research narrative arrives at the point of praxis whereby experience and theory came together to activate the PHP. The PHP was placed in the context of the national history curriculum, a review of history education literature, and situated in my teacher education work. The PHP has been represented as a system of meaning through its distinctive research processes of phenomenological inquiry, genealogical disclosure, and discursive self-fashioning. An original form of analysis was conceptualised to deconstruct the participants’ history thinking and their experiences of the cultural politics of the history curriculum.  This was conceptualised as a dismantling analysis [DA]. The third part of the narrative recounts the history class’s year of reflexive engagement with PHP. Participants’ pedagogic identities, historical thinking and critique of history curriculum and pedagogy as PHP ‘cases’ in secondary classrooms were dismantled and discussed. 

Emergent PHP findings of the participants’ thinking as beginning history teachers include such features as: discourses of embodiment (fears, failure and fraud) prior to practicum; uncertainties about historical knowledge that includes doubt and discomfort about dealing with ‘difficult’ knowledge; disillusionment with familiar historical narratives; scant exposure to Aotearoa New Zealand histories and limited engagement with historical research methods in school and university study; observations of uncritical teacher modelling of history pedagogy; questioning of a strong masculine focus in historical contexts and a recurrent theme of history as violent; history practicum experienced through the dominant orientation of history as inquiry. These findings illustrate the public, accountable and discursive production of the national history curriculum. Reimagined history curricula are glimpsed in the participants’ seeking of counter-orientations of history’s purpose and desired history pedagogy as inclusive and democratic, as social reconstruction, and as an evolving critical project. A reflective critique of the narrative research brings the writing to a close.

text: Problematised History Pedagogy as Narrative Research: Self-Fashioning, Dismantled Voices and Reimaginings in History Education A growing disturbance with history’s identity in the New Zealand schooling curriculum disrupted my educational socialisation (curriculum, professional, academic) and inheritance of educational policy decisions. In turn, this disturbance shaped a critical stance in my research and practitioner work. Accordingly, problematised history pedagogy [PHP] emerged as the phenomenon and method of my doctoral study and was activated as a counterpoint to my experiences of normalised discourses of history curriculum and pedagogy. The PHP as narrative research was situated in my history curriculum programme in a postgraduate year of secondary teacher education. The research aimed to engage my history class (research participants as preservice teachers) in pedagogy that involved critique of and reflection on the things we do as history teachers in the secondary curriculum. The PHP was nested within my historicising and theorising of educational experience. Conceptualised as a reciprocal research process, the PHP involved the participants and me in theorising pedagogies, fashioning pedagogic identities, and engaging critically with curriculum conceptions of history. The PHP sought to reimagine history curriculum and pedagogy and identify pedagogic spaces of possibility. 

	The narrative research was layered as a bricolage of storying that reflected the interdisciplinary nature of my educational socialisation. Experiences as a teacher educator, curriculum and assessment developer and researcher, meant many voices, discourses, and theories were woven into the narrative. This complex conceptual work focused on understandings of narrative; policy, curriculum and pedagogy; critical pedagogy; history; history education, and notions of space. The narrative research was constructed in three parts. Firstly, my narrative selves and shifts to a critical pedagogy stance were historicised and theorised through an autobiographical approach. An original dimension of this storying has been the use of vignettes that illuminate the convergence of educational experience, theorising, and reimaginings as an aesthetic and critical narrative device. The second part of the research narrative arrives at the point of praxis whereby experience and theory came together to activate the PHP. The PHP was placed in the context of the national history curriculum, a review of history education literature, and situated in my teacher education work. The PHP has been represented as a system of meaning through its distinctive research processes of phenomenological inquiry, genealogical disclosure, and discursive self-fashioning. An original form of analysis was conceptualised to deconstruct the participants’ history thinking and their experiences of the cultural politics of the history curriculum.  This was conceptualised as a dismantling analysis [DA]. The third part of the narrative recounts the history class’s year of reflexive engagement with PHP. Participants’ pedagogic identities, historical thinking and critique of history curriculum and pedagogy as PHP ‘cases’ in secondary classrooms were dismantled and discussed. 

Emergent PHP findings of the participants’ thinking as beginning history teachers include such features as: discourses of embodiment (fears, failure and fraud) prior to practicum; uncertainties about historical knowledge that includes doubt and discomfort about dealing with ‘difficult’ knowledge; disillusionment with familiar historical narratives; scant exposure to Aotearoa New Zealand histories and limited engagement with historical research methods in school and university study; observations of uncritical teacher modelling of history pedagogy; questioning of a strong masculine focus in historical contexts and a recurrent theme of history as violent; history practicum experienced through the dominant orientation of history as inquiry. These findings illustrate the public, accountable and discursive production of the national history curriculum. Reimagined history curricula are glimpsed in the participants’ seeking of counter-orientations of history’s purpose and desired history pedagogy as inclusive and democratic, as social reconstruction, and as an evolving critical project. A reflective critique of the narrative research brings the writing to a close.

year: 2013

title: Visualising categorical data: Linguistic case studies from te Reo Māori and New Zealand English

authors: Trye, David

subjects: visualisation

abstract: Categorical variables are prevalent in real-world datasets across numerous domains, yet few visualisation techniques accommodate them effectively. This is especially true of datasets comprising three or more categorical variables, termed multivariate categorical data. Visualising such data is challenging due to the lack of inherent ordering of nominal categories, the so-called ‘curse of dimensionality’, and the potential variability in the number of categories per variable. Corpus linguistics, which involves the study of large digital collections of naturally occurring language, serves as the primary application domain in this thesis. This domain was chosen because it is rich in multivariate categorical data and, at the same time, is often visualised using only basic techniques.

This thesis contributes to the area of categorical data visualisation in several ways. First, we propose a taxonomy of techniques for visualising categorical data, highlight limitations of existing solutions, and identify relevant analysis tasks. Building on this foundation, the thesis introduces novel techniques and enhancements for visualising datasets involving multiple categorical variables. We focus on adapting the layout and interactive capabilities of an existing technique that uses a matrix of heatmaps to represent pairwise category intersections. These modifications show that directly visualising statistical test results for categorical data can be beneficial for exploring bivariate patterns and associations. Furthermore, we contribute the design, implementation and evaluation of a novel technique called MultiCat, which is not restricted to pairwise intersections but rather facilitates analysis of relationships among multiple variables simultaneously. Both these techniques are interactive and offer greater scalability than existing alternatives, thereby affording new possibilities for analysing multivariate categorical data. However, since categorical variables can occur within more complex data structures, we also consider their presence in networks and hypergraphs, which require specialised methods.

To demonstrate the application of these techniques, we draw on two linguistic case studies that focus on languages of special significance in Aotearoa New Zealand. Addressing the low-resource status of Māori, the country’s Indigenous language, we first contribute two related Twitter datasets—a monolingual Māori corpus and a mixed–language Māori–English corpus—together with an architecture for differentiating Māori and English words. Our initial case study uses the monolingual Māori corpus and proposed visualisation techniques to investigate grammatical possession in Māori, offering fresh insights into the linguistic practices of contemporary speakers. The second case study uses networks and hypergraphs with categorical attributes to explore Māori loanword co-occurrence in New Zealand English newspaper articles. We find that loanwords tend not to occur in isolation and that New Zealanders are still importing new (unlisted) borrowings from Māori.

Ultimately, the techniques developed in this thesis have broad applications both within and beyond the corpus linguistics community. By enabling more effective visualisation and analysis of multivariate categorical data, this research has the potential to facilitate deeper insights into domains as diverse as education, healthcare, business and science.

text: Visualising categorical data: Linguistic case studies from te Reo Māori and New Zealand English Categorical variables are prevalent in real-world datasets across numerous domains, yet few visualisation techniques accommodate them effectively. This is especially true of datasets comprising three or more categorical variables, termed multivariate categorical data. Visualising such data is challenging due to the lack of inherent ordering of nominal categories, the so-called ‘curse of dimensionality’, and the potential variability in the number of categories per variable. Corpus linguistics, which involves the study of large digital collections of naturally occurring language, serves as the primary application domain in this thesis. This domain was chosen because it is rich in multivariate categorical data and, at the same time, is often visualised using only basic techniques.

This thesis contributes to the area of categorical data visualisation in several ways. First, we propose a taxonomy of techniques for visualising categorical data, highlight limitations of existing solutions, and identify relevant analysis tasks. Building on this foundation, the thesis introduces novel techniques and enhancements for visualising datasets involving multiple categorical variables. We focus on adapting the layout and interactive capabilities of an existing technique that uses a matrix of heatmaps to represent pairwise category intersections. These modifications show that directly visualising statistical test results for categorical data can be beneficial for exploring bivariate patterns and associations. Furthermore, we contribute the design, implementation and evaluation of a novel technique called MultiCat, which is not restricted to pairwise intersections but rather facilitates analysis of relationships among multiple variables simultaneously. Both these techniques are interactive and offer greater scalability than existing alternatives, thereby affording new possibilities for analysing multivariate categorical data. However, since categorical variables can occur within more complex data structures, we also consider their presence in networks and hypergraphs, which require specialised methods.

To demonstrate the application of these techniques, we draw on two linguistic case studies that focus on languages of special significance in Aotearoa New Zealand. Addressing the low-resource status of Māori, the country’s Indigenous language, we first contribute two related Twitter datasets—a monolingual Māori corpus and a mixed–language Māori–English corpus—together with an architecture for differentiating Māori and English words. Our initial case study uses the monolingual Māori corpus and proposed visualisation techniques to investigate grammatical possession in Māori, offering fresh insights into the linguistic practices of contemporary speakers. The second case study uses networks and hypergraphs with categorical attributes to explore Māori loanword co-occurrence in New Zealand English newspaper articles. We find that loanwords tend not to occur in isolation and that New Zealanders are still importing new (unlisted) borrowings from Māori.

Ultimately, the techniques developed in this thesis have broad applications both within and beyond the corpus linguistics community. By enabling more effective visualisation and analysis of multivariate categorical data, this research has the potential to facilitate deeper insights into domains as diverse as education, healthcare, business and science.

year: 2024