title: Hitting the target: Stopping active learning at the cost-based optimum

authors: Pullar-Strecker, Zac

subjects: computer science

abstract: Active learning allows machine learning models to be trained using fewer labels while retaining similar performance to traditional supervised learning. An active learner selects the most informative data points, requests their labels, and retrains itself. While this approach is promising, it raises the question of how to determine when the model is ‘good enough’ without the additional labels required for traditional evaluation. Previously, different stopping criteria have been proposed aiming to identify the optimal stopping point. Yet, optimality can only be expressed as a domain-dependent trade-off between accuracy and the number of labels, and no criterion is superior in all applications. As a further complication, a comparison of criteria for a particular real-world application would require practitioners to collect additional labelled data they are aiming to avoid by using active learning in the first place. This work enables practitioners to employ active learning by providing actionable recommendations for which stopping criteria are best for a given real-world scenario. We contribute the first large-scale comparison of stopping criteria for pool-based active learning, using a cost measure to quantify the accuracy/label trade-off, public implementations of all stopping criteria we evaluate, and an open-source framework for evaluating stopping criteria. Our research enables practitioners to substantially reduce labelling costs by utilizing the stopping criterion which best suits their domain.

text: Hitting the target: Stopping active learning at the cost-based optimum Active learning allows machine learning models to be trained using fewer labels while retaining similar performance to traditional supervised learning. An active learner selects the most informative data points, requests their labels, and retrains itself. While this approach is promising, it raises the question of how to determine when the model is ‘good enough’ without the additional labels required for traditional evaluation. Previously, different stopping criteria have been proposed aiming to identify the optimal stopping point. Yet, optimality can only be expressed as a domain-dependent trade-off between accuracy and the number of labels, and no criterion is superior in all applications. As a further complication, a comparison of criteria for a particular real-world application would require practitioners to collect additional labelled data they are aiming to avoid by using active learning in the first place. This work enables practitioners to employ active learning by providing actionable recommendations for which stopping criteria are best for a given real-world scenario. We contribute the first large-scale comparison of stopping criteria for pool-based active learning, using a cost measure to quantify the accuracy/label trade-off, public implementations of all stopping criteria we evaluate, and an open-source framework for evaluating stopping criteria. Our research enables practitioners to substantially reduce labelling costs by utilizing the stopping criterion which best suits their domain.

year: 2022

title: Alternative food networks and opportunities for transformation towards a sustainable and resilient urban food system

authors: Vieira, Leticia Canal

subjects: Local food supply

abstract: Food systems are suffering from pressures related to population growth, increased urbanisation, climate change, and resource scarcity. These pressures are exacerbated by globalisation, with consumers concentrated in urban areas while producers are dispersed across rural areas that are often remote or even in different countries. To address these challenges and create a more sustainable and resilient future, many local governments have embraced the idea of urban food systems. The literature identifies a range of sustainable and resilient outcomes for urban food systems but finding effective transition pathways remains a challenge. Alternative food networks have emerged with the goal of being more environmentally sustainable and socially just. A systematic literature review was conducted to identify how alternative food networks can contribute to achieving sustainable and resilient urban food systems. The analysis of 50 international case studies showed that alternative food networks may be able to create a food provision system that contributes to: the generation, transfer, and appropriate use of food knowledge and skills; the protection of surrounding ecosystems; more participative decision processes; improved local food supply; and, increased connectivity between urban and rural areas. Social justice and product diversity, however, are issues that remain a challenge. The paper concludes with insights for supporting Australian alternative food networks, including: the further evaluation of alternative food networks capacity of reducing green-house gas emissions and food loss and waste; the inclusion of alternative food networks as a possible climate change adaptation strategy for urban food supply; and an analysis of how governance arrangements can better support these initiatives.

text: Alternative food networks and opportunities for transformation towards a sustainable and resilient urban food system Food systems are suffering from pressures related to population growth, increased urbanisation, climate change, and resource scarcity. These pressures are exacerbated by globalisation, with consumers concentrated in urban areas while producers are dispersed across rural areas that are often remote or even in different countries. To address these challenges and create a more sustainable and resilient future, many local governments have embraced the idea of urban food systems. The literature identifies a range of sustainable and resilient outcomes for urban food systems but finding effective transition pathways remains a challenge. Alternative food networks have emerged with the goal of being more environmentally sustainable and socially just. A systematic literature review was conducted to identify how alternative food networks can contribute to achieving sustainable and resilient urban food systems. The analysis of 50 international case studies showed that alternative food networks may be able to create a food provision system that contributes to: the generation, transfer, and appropriate use of food knowledge and skills; the protection of surrounding ecosystems; more participative decision processes; improved local food supply; and, increased connectivity between urban and rural areas. Social justice and product diversity, however, are issues that remain a challenge. The paper concludes with insights for supporting Australian alternative food networks, including: the further evaluation of alternative food networks capacity of reducing green-house gas emissions and food loss and waste; the inclusion of alternative food networks as a possible climate change adaptation strategy for urban food supply; and an analysis of how governance arrangements can better support these initiatives.

year: 2020

title: How Māori precariate families navigate social services

authors: King, Delta

abstract: We are living in a period in which the increasingly precarious nature of employment and welfare support systems has dramatically amplified the hardships faced by many people.¹ Correspondingly, much still needs to be written about the rise of the precariat. ² International literature asserts that post World War II paid employment was commonly full-time and secure up until the 1970s, when the rise of more insecure work increased as neoliberal policies and globalisation began dominating public deliberations regarding work and social life. ³ Subsequent recessions across many OECD countries contributed to labour market transformations back towards increased 'flexibility' and- the casualisation of employment. These labour market shifts have resulted in insecure work and income situations for many households, which for some means frequent cycles of paid employment and welfare dependency. People experiencing such insecure employment face insecure and unliveable incomes while grappling with inadequate state support - these are the people increasingly known as 'the precariat'.

text: How Māori precariate families navigate social services We are living in a period in which the increasingly precarious nature of employment and welfare support systems has dramatically amplified the hardships faced by many people.¹ Correspondingly, much still needs to be written about the rise of the precariat. ² International literature asserts that post World War II paid employment was commonly full-time and secure up until the 1970s, when the rise of more insecure work increased as neoliberal policies and globalisation began dominating public deliberations regarding work and social life. ³ Subsequent recessions across many OECD countries contributed to labour market transformations back towards increased 'flexibility' and- the casualisation of employment. These labour market shifts have resulted in insecure work and income situations for many households, which for some means frequent cycles of paid employment and welfare dependency. People experiencing such insecure employment face insecure and unliveable incomes while grappling with inadequate state support - these are the people increasingly known as 'the precariat'.

year: 2017