121 research outputs found
Abstraction in directed model checking
Abstraction is one of the most important issues to cope with large and infinite state spaces in model checking and to reduce the verification efforts. The abstract system is smaller than the original one and if the abstract system satisfies a correctness specification, so does the concrete one. However, abstractions may introduce a behavior violating the specification that is not present in the original system.
This paper bypasses this problem by proposing the combination of abstraction with heuristic search to improve error detection. The abstract system is explored in order to create a database that stores the exact distances from abstract states to the set of abstract error states. To check, whether or not the abstract behavior is present in the original system, effcient exploration algorithms exploit the database as a guidance
Property-Based Testing - The ProTest Project
The ProTest project is an FP7 STREP on property based testing. The purpose of the project is to develop software engineering approaches to improve reliability of service-oriented networks; support fault-finding and diagnosis based on specified properties of the system. And to do so we will build automated tools that will generate and run tests, monitor execution at run-time, and log events for analysis.
The Erlang / Open Telecom Platform has been chosen as our initial implementation vehicle due to its robustness and reliability within the telecoms sector. It is noted for its success in the ATM telecoms switches by Ericsson, one of the project partners, as well as for multiple other uses such as in facebook, yahoo etc. In this paper we provide an overview of the project goals, as well as detailing initial progress in developing property based testing techniques and tools for the concurrent functional programming language Erlang
Lessons from Formally Verified Deployed Software Systems (Extended version)
The technology of formal software verification has made spectacular advances,
but how much does it actually benefit the development of practical software?
Considerable disagreement remains about the practicality of building systems
with mechanically-checked proofs of correctness. Is this prospect confined to a
few expensive, life-critical projects, or can the idea be applied to a wide
segment of the software industry?
To help answer this question, the present survey examines a range of
projects, in various application areas, that have produced formally verified
systems and deployed them for actual use. It considers the technologies used,
the form of verification applied, the results obtained, and the lessons that
can be drawn for the software industry at large and its ability to benefit from
formal verification techniques and tools.
Note: a short version of this paper is also available, covering in detail
only a subset of the considered systems. The present version is intended for
full reference.Comment: arXiv admin note: text overlap with arXiv:1211.6186 by other author
CONTREX: Design of embedded mixed-criticality CONTRol systems under consideration of EXtra-functional properties
The increasing processing power of today’s HW/SW platforms leads to the integration of more and more functions in a single device. Additional design challenges arise when these functions share computing resources and belong to different criticality levels. CONTREX complements current activities in the area of predictable computing platforms and segregation mechanisms with techniques to consider the extra-functional properties, i.e., timing constraints, power, and temperature. CONTREX enables energy efficient and cost aware design through analysis and optimization of these properties with regard to application demands at different criticality levels. This article presents an overview of the CONTREX European project, its main innovative technology (extension of a model based design approach, functional and extra-functional analysis with executable models and run-time management) and the final results of three industrial use-cases from different domain (avionics, automotive and telecommunication).The work leading to these results has received funding from the European Community’s Seventh Framework Programme FP7/2007-2011 under grant agreement no. 611146
Specifying and analysing institutions in multi-agent systems using answer set programming
It is recognised that normative systems, and in particular electronic institutions and contracts are a potentially powerful means for making agent interactions in multi-agent systems effective and efficient. However, correctly specifying the behaviour of such systems is a difficult problem. Designers are faced with two concurrent, complex tasks: firstly they must specify the relationships (over time) between agents’ actions and their effects, and secondly they must also consider how agents’ actions are to be regulated through the definition of agents’ permissions and obligations. Such systems are typi- cally complex, and given this complexity it may be difficult for a designer to determine whether their original objectives have been captured by the specification of the system. In this dissertation we seek to address some of the problems associated with institu- tional specification. In order to do this we present a model for specifying institutions based on the notion of socially constructed reality that accounts not only for how the action and events which constitute the institution are described, but also how they are regulated. Institutions may be used in a number of ways, and may account for concepts at varying levels of abstraction. Recognising this we also investigate how several insti- tutions, each accounting for a particular aspect of a society may be composed and how the relationships between these institutions may be expressed. Given this model, we then demonstrate how, using the answer set programming paradigm institutional spec- ifications based on our model may be checked for the absence or presence of certain (un)desirable properties.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
The assertive presidency – understanding preemptive executive pressure on foreign policy legislation in the US
The specter of an increasingly uneven distribution of power between the Executive Branch and Congress looms large in scholarship on the separation of powers in American government. This is particularly evident in the design and exercise of foreign policy. While the presidents’ use of legislative powers like the veto has been studied extensively, I argue that preemptive presidential interventions during the process of lawmaking are a subtler and less politically costly tool that is more important than scholars realized. This project focuses on American foreign policy lawmaking and examines the extent to which it is characterized by presidential assertiveness communicated to Congress through a hitherto understudies tool of executive intervention. Specifically, I seek to understand how contemporary presidents use Statements of Administration Policy (SAPs), a relatively new class of executive communications designed to preemptively intervene in key legislation as it is drafted in Congress. Delivered at a crucial intervention point along the legislative process, these communications provide a key opportunity for presidents to challenge specific provisions. Embedded in the broader discourse on struggling congressional checks on the executive, this project fills a gap in the understanding of the dynamics that shape the balance of power between Congress and the president. I find that interbranch confrontations increased significantly after the critical juncture of 9/11 and that Congress gradually expanded the use of its authorization leverage over time. In addition, two contextual predictors of increasing presidential assertiveness in preemptive messages to Congress stand out: divided government and presidential election years. My results indicate that presidents still cannot achieve many of their foreign policy goal without negotiating with Congress within contested bargaining procedures. Overall, my dissertation makes three principal contributions to the ongoing research on domestic underpinnings of US foreign policy: First, my findings quality the image of unchecked presidential discretion and highlight the continuous relevance of interbranch contestation in foreign policy. Second, I show that the mechanisms of change as laid out by historical institutionalism are useful for explaining long-term shifts in interbranch dynamics. Third, I introduce a novel assertiveness-score based on a relatively new source of presidential position language, which can be adapted for other research purposes
Inter-workgroup barrier synchronisation on graphics processing units
GPUs are parallel devices that are able to run thousands of
independent threads concurrently. Traditional GPU programs are
data-parallel, requiring little to no communication,
i.e. synchronisation, between threads. However, classical concurrency
in the context of CPUs often exploits synchronisation idioms that are
not supported on GPUs. By studying such idioms on GPUs, with an aim to
facilitate them in a portable way, a wider and more generic space of
GPU applications can be made possible.
While the breadth of this thesis extends to many aspects of GPU
systems, the common thread throughout is the global barrier: an
execution barrier that synchronises all threads executing a GPU
application. The idea of such a barrier might seem straightforward,
however this investigation reveals many challenges and insights. In
particular, this thesis includes the following studies:
Execution models: while a general global barrier can deadlock due to
starvation on GPUs, it is shown that the scheduling guarantees of
current GPUs can be used to dynamically create an execution
environment that allows for a safe and portable global barrier
across a subset of the GPU threads.
Application optimisations: a set GPU optimisations are examined that
are tailored for graph applications, including one optimisation
enabled by the global barrier. It is shown that these optimisations
can provided substantial performance improvements, e.g. the barrier
optimisation achieves over a 10X speedup on AMD and Intel GPUs. The
performance portability of these optimisations is investigated, as
their utility varies across input, application, and architecture.
Multitasking: because many GPUs do not support preemption,
long-running GPU compute tasks (e.g. applications that use the
global barrier) may block other GPU functions, including graphics. A
simple cooperative multitasking scheme is proposed that allows
graphics tasks to meet their deadlines with reasonable overheads.Open Acces
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