3,894 research outputs found
COVID-19 Vaccines: Characterizing Misinformation Campaigns and Vaccine Hesitancy on Twitter
Vaccine hesitancy and misinformation on social media has increased concerns
about COVID-19 vaccine uptake required to achieve herd immunity and overcome
the pandemic. However anti-science and political misinformation and
conspiracies have been rampant throughout the pandemic. For COVID-19 vaccines,
we investigate misinformation and conspiracy campaigns and their characteristic
behaviours. We identify whether coordinated efforts are used to promote
misinformation in vaccine related discussions, and find accounts coordinately
promoting a `Great Reset' conspiracy group promoting vaccine related
misinformation and strong anti-vaccine and anti-social messages such as boycott
vaccine passports, no lock-downs and masks. We characterize other
misinformation communities from the information diffusion structure, and study
the large anti-vaccine misinformation community and smaller anti-vaccine
communities, including a far-right anti-vaccine conspiracy group. In comparison
with the mainstream and health news, left-leaning group, which are more
pro-vaccine, the right-leaning group is influenced more by the anti-vaccine and
far-right misinformation/conspiracy communities. The misinformation communities
are more vocal either specific to the vaccine discussion or political
discussion, and we find other differences in the characteristic behaviours of
different communities. Lastly, we investigate misinformation narratives and
tactics of information distortion that can increase vaccine hesitancy, using
topic modeling and comparison with reported vaccine side-effects (VAERS)
finding rarer side-effects are more frequently discussed on social media
The natural history of bugs: using formal methods to analyse software related failures in space missions
Space missions force engineers to make complex trade-offs between many different constraints including cost, mass, power, functionality and reliability. These constraints create a continual need to innovate. Many advances rely upon software, for instance to control and monitor the next generation ‘electron cyclotron resonance’ ion-drives for deep space missions.Programmers face numerous challenges. It is extremely difficult to conduct valid ground-based tests for the code used in space missions. Abstract models and simulations of satellites can be misleading. These issues are compounded by the use of ‘band-aid’ software to fix design mistakes and compromises in other aspects of space systems engineering. Programmers must often re-code missions in flight. This introduces considerable risks. It should, therefore, not be a surprise that so many space missions fail to achieve their objectives. The costs of failure are considerable. Small launch vehicles, such as the U.S. Pegasus system, cost around 4 million up to 73 million from the failure of a single uninsured satellite. It is clearly important that we learn as much as possible from those failures that do occur. The following pages examine the roles that formal methods might play in the analysis of software failures in space missions
Complexity Hierarchies Beyond Elementary
We introduce a hierarchy of fast-growing complexity classes and show its
suitability for completeness statements of many non elementary problems. This
hierarchy allows the classification of many decision problems with a
non-elementary complexity, which occur naturally in logic, combinatorics,
formal languages, verification, etc., with complexities ranging from simple
towers of exponentials to Ackermannian and beyond.Comment: Version 3 is the published version in TOCT 8(1:3), 2016. I will keep
updating the catalogue of problems from Section 6 in future revision
A Web-Based Tool for Analysing Normative Documents in English
Our goal is to use formal methods to analyse normative documents written in
English, such as privacy policies and service-level agreements. This requires
the combination of a number of different elements, including information
extraction from natural language, formal languages for model representation,
and an interface for property specification and verification. We have worked on
a collection of components for this task: a natural language extraction tool, a
suitable formalism for representing such documents, an interface for building
models in this formalism, and methods for answering queries asked of a given
model. In this work, each of these concerns is brought together in a web-based
tool, providing a single interface for analysing normative texts in English.
Through the use of a running example, we describe each component and
demonstrate the workflow established by our tool
Weak Alternating Timed Automata
Alternating timed automata on infinite words are considered. The main result
is a characterization of acceptance conditions for which the emptiness problem
for these automata is decidable. This result implies new decidability results
for fragments of timed temporal logics. It is also shown that, unlike for MITL,
the characterisation remains the same even if no punctual constraints are
allowed
Theory of reliable systems
The analysis and design of reliable systems are discussed. The attributes of system reliability studied are fault tolerance, diagnosability, and reconfigurability. Objectives of the study include: to determine properties of system structure that are conducive to a particular attribute; to determine methods for obtaining reliable realizations of a given system; and to determine how properties of system behavior relate to the complexity of fault tolerant realizations. A list of 34 references is included
Specification and Verification of Media Constraints using UPPAAL
We present the formal specification and verification of a multimedia stream. The stream is described in a timed automata notation. We verify that the stream satisfies certain quality of service properties, in particular, throughput and end-to-end latency. The verification tool used is the real-time model checker UPPAAL
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