Circus Models for Safety-Critical Java Programs

Safety-critical Java (SCJ) is a restriction of the real-time specification for Java to support the development and certification of safety-critical applications. The SCJ technology specification is the result of an international effort from industry and academia. In this paper, we present a formalization of the SCJ Level 1 execution model, formalize a translation strategy from SCJ into a refinement notation and describe a tool that largely automates the generation of the formal models. Our modelling language is part of the Circus family; at the core, we have Z, communicating sequential processes and Morgan’s calculus, but we also use object-oriented and timed constructs from the OhCircus and Circus Time variants. Our work is an essential ingredient for the development of refinement-based reasoning techniques for SCJ

A programming logic for Java bytecode programs

One significant disadvantage of interpreted bytecode languages, such as Java, is their low execution speed in comparison to compiled languages like C. The mobile nature of bytecode adds to the problem, as many checks are necessary to ensure that downloaded code from untrusted sources is rendered as safe as possible. But there do exist ways of speeding up such systems. One approach is to carry out static type checking at load time, as in the case of the Java Bytecode Verifier. This reduces the number of runtime checks that must be done and also allows certain instructions to be replaced by faster versions. Another approach is the use of a Just In Time (JIT) Compiler, which takes the bytecode and produces corresponding native code at runtime. Some JIT compilers also carry out some code optimization. There are, however, limits to the amount of optimization that can safely be done by the Verifier and JITs; some operations simply cannot be carried out safely without a certain amount of runtime checking. But what if it were possible to prove that the conditions the runtime checks guard against would never arise in a particular piece of code? In this case it might well be possible to dispense with these checks altogether, allowing optimizations not feasible at present. In addition to this, because of time constraints, current JIT compilers tend to produce acceptable code as quickly as possible, rather than producing the best code possible. By removing the burden of analysis from them it may be possible to change this. We demonstrate that it is possible to define a programming logic for bytecode programs that allows the proof of bytecode programs containing loops. The instructions available to use in the programs are currently limited, but the basis is in place to extend these. The development of this logic is non-trivial and addresses several difficult problems engendered by the unstructured nature of bytecode programs

People of mixed blood: ethnicity, personhood and sociality in East Java, Indonesia

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Code mobility and Java RMI

Imperial Users onl

Developing a catalogue of errors and evaluating its impact on software development

The development of quality software is of paramount importance, yet this has been and continues to be an elusive goal for software engineers. Delivered software often fails due to errors that are injected during its development. Correcting these errors early in the development or preventing them altogether can, therefore, be considered as one way to improve software quality. In this thesis, the development of a Catalogue of Errors is described. Field studies with senior software engineering students are used to confirm that developers using the Catalogue of Errors commit fewer errors in their development artifacts. The impact of the Catalogue of Errors on productivity is also examined

Vulnerability, livelihoods and disaster knowledge in the volcanic highlands of Central Java, Indonesia: 'Itu sudah biasa'

This thesis describes the interaction of vulnerability, livelihoods and disaster knowledge in a volcanic area of Central Java, Indonesia. The Dieng Plateau is a volcanically hazardous landscape, featuring a series of craters with a history of recurrent phreatic eruptions and emissions of poisonous gases. While the government manages this hazard through largely technocratic interventions, for local farmers the hazard is integrated with, and a normal part of, daily life (‘itu sudah biasa’). Farmers respond to heightened volcanic activity in an informed manner, while at times taking greater risks for the achievement of the often-lucrative livelihood goals that can help alleviate local vulnerabilities. Despite boasting 127 active volcanoes, there is sill a scarcity of studies that focus on the construction of vulnerability in Indonesia’s volcanic areas. Furthermore, current disaster scholarship is yet to comprehensively describe crucial factors that influence this vulnerability, such as expert and political constructions of risk, and the benefits gained through partaking in livelihoods in volcanic landscapes. By drawing on a multi-methods and largely qualitative approach, combining semi-structured and unstructured interviews with farmers, observation of government-run exercises, a participatory workshop, and household survey, this thesis responds to these research needs. Throughout the three empirical chapters of this thesis, I describe and relate the many and varied ways vulnerabilities are produced, or overcome, in this volcanic landscape. The first conceptualisation of vulnerability argues that it is a product of access to land resources, influenced by Dieng’s history of upland settlement, the unequal spatial distribution of land prices, and the impact of internal state-led territorialisation strategies. I expand on current vulnerability frameworks used within disaster scholarship; specifically the access model and concept of the ‘hazardscape’, to argue that vulnerabilities are also produced through the way governments define and territorialise hazardous land. The second conceptualisation of vulnerability relates it to livelihood outcomes and the impact of a major potato crop boom. By integrating the disaster and agrarian literature, I question dominant views that rural livelihoods in volcanic areas are inherently ‘unsustainable’, and present a holistic picture of volcanic risk, considering capacity alongside vulnerability. The third conceptualisation of vulnerability is related to disaster knowledge and the risk mitigation activities this knowledge informs. I expand on current approaches to the study of disaster knowledge to argue that both local and expert knowledge are locally contextualised and hybrid systems. While they differ in various aspects, they are not separate from, but rather actively inform, the other. The thesis concludes with a discussion of how these three conceptualisations of vulnerability, when combined, can contribute to a more holistic, practical, and contextualised approach to volcanic risk reduction in the Dieng Plateau. This thesis argues that vulnerability to volcanic hazard in the Dieng Plateau is produced through the social, economic, political and environmental processes that govern access to land and livelihood outcomes, while also emerging through the way governments and locals alike define and respond to volcanic activity. This finding bears important lessons for the development of future policies aimed to reduce, or overcome the creation of new, risks in other agriculturally dominated volcanic landscapes throughout Indonesia

Subaltern agency and the political economy of rural social change

Twenty years after the fall of Suharto in Indonesia, most political studies of Indonesia’s post-New Order democratic ‘transition’ have left the ideas, forms of organisation, strategies and impacts of lower class struggles largely unexamined. Scholarly works that address the dynamics of social and political change have largely focussed on the mixed outcomes of decentralisation and democratisation of state power for elite actors since Reformasi, providing little or no framework for conceptualising popular political action in the context of this institutional restructuring. Drawing on propositions from Marxist political economy, Gramsci’s concept of hegemony and social reproduction theory, this thesis develops analytical approaches for investigating the dynamics of rural subaltern agency in post-New Order Indonesia, focussing on how rural subaltern actors ‘do politics’. The approach applied here extends the analysis of political studies beyond the state, its institutions and hegemonic practices by focussing on the persistent, albeit often fragmented, popular struggles to secure control of resources and shift social relations of power in favour of subaltern and other non-elite classes. It considers the connections between everyday popular encroachments on hegemonic power, social movement struggles and moments of social and political crisis with the potential for transformative social and political change. Using qualitative data from extensive fieldwork in Central Java, the thesis demonstrates that legacies of subaltern struggles over power and land as a resource are reflected in villagers’ contemporary relations with state institutions and other forms of social organisation. They organise across multiple scales, and employ diverse tactics including shifting alliances with other social actors to further their interests. Their political claims are strongly informed by cultures and ideologies that have their roots in previous periods of collective action, which are reproduced or transformed though their experiences in contemporary social struggles. Finally, the thesis considers how these diverse expressions of subaltern social struggles might contribute to progressive forms of agrarian development and the broadening and deepening of pro-poor democratic struggles in Indonesia