Fault-tolerant routing in peer-to-peer systems

We consider the problem of designing an overlay network and routing mechanism that permits finding resources efficiently in a peer-to-peer system. We argue that many existing approaches to this problem can be modeled as the construction of a random graph embedded in a metric space whose points represent resource identifiers, where the probability of a connection between two nodes depends only on the distance between them in the metric space. We study the performance of a peer-to-peer system where nodes are embedded at grid points in a simple metric space: a one-dimensional real line. We prove upper and lower bounds on the message complexity of locating particular resources in such a system, under a variety of assumptions about failures of either nodes or the connections between them. Our lower bounds in particular show that the use of inverse power-law distributions in routing, as suggested by Kleinberg (1999), is close to optimal. We also give efficient heuristics to dynamically maintain such a system as new nodes arrive and old nodes depart. Finally, we give experimental results that suggest promising directions for future work.Comment: Full version of PODC 2002 paper. New version corrects missing conditioning in Lemma 9 and some related details in the proof of Theorem 10, with no changes to main result

Strategies and Approaches to Ensure Equitable Access to Quality Education in Economic Crises

This helpdesk review has drawn primarily on evidence from systematic reviews and synthesis studies focused on (i) the impact of economic crises on education systems, and (ii) the effectiveness of strategies and approaches that aim to improve educational participation. It has focused on policy responses at the primary and secondary levels of education, and where possible has drawn on examples from effective responses in the context of large-scale economic crisis. Where evidence was not available from contexts of economic crisis, studies from resource-constrained low- and middle- income countries (LMICs) were considered. Economic crises pose particular challenges to the achievement of goals around equitable access to quality education. Falling household incomes can affect the ‘demand’ for schooling, increasing the cost of schooling, particularly for the poorest. Meanwhile, constrained government budgets can lead to reduced investments in schools and teachers, and associated declines in education quality (World Bank 2009). This review discusses five strategies and approaches to ensure equitable access to quality education, which have been identified as appropriate responses in literature on the impact of economic crisis on education (Lundberg and Wuermli 2012; Shafiq 2010; World Bank 2009). These are: (1) cash transfers; (2) scholarship programmes and fee waivers; (3) school feeding; (4) decentralisation and school grants; and (5) information-related activities. For all except ‘information-related activities’, there are examples of the effective implementation of that policy in contexts of economic crisis

Teacher Motivation in Economic Crises

This helpdesk review presents evidence of strategies and approaches that have worked to motivate teachers, with a focus on applications to contexts facing the sudden shock of economic crisis. It begins by presenting an overview of the ways in which economic crisis can impact education systems, drawing on recent relevant examples and presenting a detailed case study of Greece. It then moves on to review frameworks to understand teacher motivation, identifying the different factors that may be important in improving teacher motivation. Finally it presents evidence of strategies and approaches to improve teacher motivation. Evidence of strategies and approaches taken to explicitly improve teacher motivation in the context of the sudden shock of economic crisis is minimal. The examples of Greece, Indonesia, Venezuela, Argentina, Russia and beyond were consulted, and whilst there was some documentation of the impact of economic crisis in these contexts, there was very limited documentation of strategies and approaches taken to mitigate the effects of crisis on teachers. Evidence of strategies and approaches beyond financial incentives was also limited, even when considering a broader set of contexts. The focus of this review is therefore on strategies and approaches that have worked in resource-constrained LMIC contexts, whilst situating the discussion in the context of the ways in which economic crisis can (and has) impacted on education systems

Language and Learning in Ethiopia

This thesis examines the relationship between language of instruction policy and educational outcomes in Ethiopia. In 1994 Ethiopia introduced a mother tongue education policy which marked a move away from Amharic-only instruction, to the use of multiple local languages in primary schooling. This thesis investigates three key dimensions of this policy: (i) whether there is an advantage to being a ‘mother tongue learner’ in terms of learning outcomes; (ii) whether there are inequalities in learning progress between students learning in different languages of instruction, and if so, why; and (iii) whether the use of multiple mother tongues for school instruction can ensure access to essential languages of wider communication, and if not, with what implications. The mixed methods analysis finds that (i) there is an advantage to being a ‘mother tongue learner’ in Amharic language classes, but this advantage disappears when other indicators of educational experience are taken into account, and varies between linguistic environments/ contexts; (ii) that stakeholders support the use of mother tongue for reasons that relate both to pedagogy, and to the assertion of ethnolinguistic identity, emphasising the nonlearning-related benefits of the policy; (iii) that between-language of instruction inequality of learning outcomes are evident, with students learning in many of the newly introduced languages of instruction making less progress in mathematics than their counterparts in Amharic language of instruction classrooms; (iv) that these between-language inequalities in learning outcomes may be explained by variation in literate environments and linguistic development and standardisation, as well as heterogeneity of school quality between different linguistic communities; and (v) that stakeholders perceive important inequalities in opportunities to acquire languages of wider communication (Amharic and English) between students learning in different languages of instruction, raising important concerns about the extent to which the policy can translate into social and economic opportunity and mobility for all

"There are too many, but never enough": qualitative case study investigating routine coding of clinical information in depression.

We sought to understand how clinical information relating to the management of depression is routinely coded in different clinical settings and the perspectives of and implications for different stakeholders with a view to understanding how these may be aligned

An Overview of ICT for Education of Refugees and IDPs

This rapid review examined examples of ICT approaches to address the education needs of those living in IDP and refugee camps and lessons learned from these experiences. Although ICT is considered a good system to fulfil the education needs within refugee settings, many studies conclude that access to ICTs in schools or at home is not sufficient to improve learning outcomes. It is due to the role of a mentor or tutor figure is seen as key to productive learner engagement with technology, and the effectiveness of ICT-based education is reliant on appropriate teacher training to ensure successful up-take at the classroom level (Tauson & Stannard 2018: 47, 62; UNESCO 2018: 74; Carlson 2013: 30). Secondly, in terms of content, ICTs for education should provide content that is responsive or adaptable to the learners’ level, is implemented in line with the local curriculum and also is relevant to the learners’ context (Tauson & Stannard 2018: 36-38, 61). Despite this potential for ICTs, there remains a broad lack of evidence related to education in refugee settings (Burde et al. 2015; Tauson & Stannard 2018; World Bank 2016). In particular, more information is needed on pedagogic design, on the effective use of ICTs for learning, on the role of ICTs in ensuring continuity of and linkages between learning in formal and non-formal settings, on the role of ICTs in educational data-gathering, and on the cost-effectiveness of ICT-led interventions (Burde et al 2015; Tausin & Stannard 2018; Carlson 2013). In light of the availability of evidence, some of the studies cited here instead supplement their findings by drawing on observational studies, and on studies on effective ICT usage from learners in non-refugee contexts (Burde et al. 2015; Tauson & Stannard 2018)

The Effectiveness of School Grants in Low- and Middle-Income Contexts

This helpdesk review has drawn primarily on evidence from systematic reviews and synthesis studies focused on the effectiveness of school grants for the improvement of (i) equitable access to quality education, and (ii) the student learning outcomes. The rationale for school grants has emerged as part of relatively recent policy-driven practices for educational decentralisation and, within that, school-based decision-making. The devolution of a range of decisions to the school-level is assumed to improve accountability, efficiency and responsiveness to local needs (Bruns et al. 2011; Carr-Hill et al. 2016; Slater 2013). These decisions may include concerns related to curricula, finance, management and teachers, and may be taken at one or more administrative level (Bruns et al. 2011; Slater 2013). The literature identifies several key principles for effective implementation. This includes an acknowledgement of the range of challenges and barriers that are associated with the implementation of these type of models at the school level, including (i) the need for all actors to support the principles of decision-making reform; (ii) the need for local district support; and (iii) the reality that this type of reform places increased time and work demands on teachers and parents (Bruns et al. 2011). The review found that evidence of the effectiveness of school grant policies for equitable access to quality education was limited. Few studies provided rigorous examinations of the impact of school grants on equity of access across a range of measures, for example between rural/ urban locations, gender, or socio-economic status. The evidence base is relatively stronger in relation to the effectiveness of school grant policies for student learning outcomes, being suggestive of small but positive impacts. However, according to a 2016 synthesis study, these positive results are concentrated in middle-income countries, and stronger impacts tend to be found for wealthier students with more educated parents, with smaller effects found in disadvantaged communities (Carr-Hill et al. 2016; see also Hanushek et al. 2011; UNESCO 2017)