1,010 research outputs found
Falsification of Cyber-Physical Systems with Robustness-Guided Black-Box Checking
For exhaustive formal verification, industrial-scale cyber-physical systems
(CPSs) are often too large and complex, and lightweight alternatives (e.g.,
monitoring and testing) have attracted the attention of both industrial
practitioners and academic researchers. Falsification is one popular testing
method of CPSs utilizing stochastic optimization. In state-of-the-art
falsification methods, the result of the previous falsification trials is
discarded, and we always try to falsify without any prior knowledge. To
concisely memorize such prior information on the CPS model and exploit it, we
employ Black-box checking (BBC), which is a combination of automata learning
and model checking. Moreover, we enhance BBC using the robust semantics of STL
formulas, which is the essential gadget in falsification. Our experiment
results suggest that our robustness-guided BBC outperforms a state-of-the-art
falsification tool.Comment: Accepted to HSCC 202
Second-Order Finite Automata
Traditionally, finite automata theory has been used as a framework for the representation of possibly infinite sets of strings. In this work, we introduce the notion of second-order finite automata, a formalism that combines finite automata with ordered decision diagrams, with the aim of representing possibly infinite sets of sets of strings. Our main result states that second-order finite automata can be canonized with respect to the second-order languages they represent. Using this canonization result, we show that sets of sets of strings represented by second-order finite automata are closed under the usual Boolean operations, such as union, intersection, difference and even under a suitable notion of complementation. Additionally, emptiness of intersection and inclusion are decidable. We provide two algorithmic applications for second-order automata. First, we show that several width/size minimization problems for deterministic and nondeterministic ODDs are solvable in fixed-parameter tractable time when parameterized by the width of the input ODD. In particular, our results imply FPT algorithms for corresponding width/size minimization problems for ordered binary decision diagrams (OBDDs) with a fixed variable ordering. Previously, only algorithms that take exponential time in the size of the input OBDD were known for width minimization, even for OBDDs of constant width. Second, we show that for each k and w one can count the number of distinct functions computable by ODDs of width at most w and length k in time h(|ÎŁ|,w) â‹… kO(1), for a suitable . This improves exponentially on the time necessary to explicitly enumerate all such functions, which is exponential in both the width parameter w and in the length k of the ODDs.publishedVersio
Designing Trustworthy Autonomous Systems
The design of autonomous systems is challenging and ensuring their trustworthiness can have different meanings, such as i) ensuring consistency and completeness of the requirements by a correct elicitation and formalization process; ii) ensuring that requirements are correctly mapped to system implementations so that any system behaviors never violate its requirements; iii) maximizing the reuse of available components and subsystems in order to cope with the design complexity; and iv) ensuring correct coordination of the system with its environment.Several techniques have been proposed over the years to cope with specific problems. However, a holistic design framework that, leveraging on existing tools and methodologies, practically helps the analysis and design of autonomous systems is still missing. This thesis explores the problem of building trustworthy autonomous systems from different angles. We have analyzed how current approaches of formal verification can provide assurances: 1) to the requirement corpora itself by formalizing requirements with assume/guarantee contracts to detect incompleteness and conflicts; 2) to the reward function used to then train the system so that the requirements do not get misinterpreted; 3) to the execution of the system by run-time monitoring and enforcing certain invariants; 4) to the coordination of the system with other external entities in a system of system scenario and 5) to system behaviors by automatically synthesize a policy which is correct
A virtual factory for smart city service integration
Tese de Doutoramento em Informática (MAP-i)In the context of smart cities, governments are investing efforts on creating public
value through the development of digital public services (DPS) focusing on specific
policy areas, such as transport. Main motivations to deliver DPS include reducing
administrative burdens and costs, increasing effectiveness and efficiency of government
processes, and improving citizens’ quality of life through enhanced services and simplified
interactions with governments.
To ensure effective planning and design of DPS in a given domain, governments face
several challenges, like the need of specialized tools to facilitate the effective planning
and the rapid development of DPS, as well as, tools for service integration, affording
high development costs, and ensuring DPS conform with laws and regulations.
These challenges are exacerbated by the fact that many public administrations develop
tailored DPS, disregarding the fact that services share common functionality
and business processes.
To address the above challenges, this thesis focuses on leveraging the similarities of
DPS and on applying a Software Product Line (SPL) approach combined with formal
methods techniques for specifying service models and verifying their behavioural properties.
In particular, the proposed solution introduces the concept of a virtual factory
for the planning and rapid development of DPS in a given smart city domain. The
virtual factory comprises a framework including software tools, guidelines, practices,
models, and other artefacts to assist engineers to automate and make more efficient
the development of a family of DPS.
In this work the virtual factory is populated with tools for government officials and
software developers to plan and design smart mobility services, and to rapidly model
DPS relying on SPLs and components-base development techniques.
Specific contributions of the thesis include: 1) the concept of virtual factory; 2)
a taxonomy for planning and designing smart mobility services; 3) an ontology to fix
a common vocabulary for a specific family of DPS; 4) a compositional formalism to
model SPLs, to serve as a specification language for DPS; and 5) a variable semantics
for a coordination language to simplify coordination of services in the context of SPLs.No contexto das cidades inteligentes, os governos investem esforços na criação de valor
público através do desenvolvimento de serviços públicos digitais (DPS), concentrandose
em áreas polĂticas especĂficas, como os transportes. As principais motivações para
entregar o DPS incluem a redução de custos administrativos, o aumento da eficácia
dos processos do governo e a melhoria da qualidade de vida dos cidadãos através de
serviços melhorados e interações simplificadas com os governos.
Para garantir um planeamento efetivo do DPS num determinado domĂnio, os governos
enfrentam vários desafios, como a necessidade de ferramentas especializadas para
facilitar o planeamento eficaz e o rápido desenvolvimento do DPS, bem como ferramentas
para integração de DPS, reduzindo altos custos de desenvolvimento e garantindo
que os DPS estejam em conformidade com as leis e regulamentos.
Esses desafios são exacerbados pelo fato de que muitas administrações públicas
desenvolvem o DPS sob medida, desconsiderando o fato de que os serviços compartilham
funcionalidade e processos de negĂłcios comuns.
Para enfrentar os desafios, esta tese concentra-se em aproveitar as semelhanças dos
DPS aplicando uma abordagem de Software Product Lines (SPL) combinada com métodos
formais para especificar modelos de DPS e verificar propriedades. Em particular,
introduz o conceito de uma fábrica virtual (VF) para o planeamento e desenvolvimento
rápido de DPS num domĂnio de cidade inteligente. A VF compreende ferramentas de
software, diretrizes, modelos e outros artefatos para auxiliar os engenheiros a automatizar
e tornar mais eficiente o desenvolvimento de uma famĂlia de DPS.
Neste trabalho, a VF é preenchida com ferramentas para várias partes para planear
e projetar serviços de mobilidade inteligente (MI), e modelar rapidamente o DPS com
base em SPLs e técnicas de desenvolvimento baseadas em componentes.
Contribuições especĂficas da tese incluem: 1) o conceito de VF; 2) uma taxonomia
para planear serviços de MI; 3) uma ontologia para fixar um vocabulário comum para
uma famĂlia especĂfica de DPS; 4) um formalismo composicional para modelar SPLs,
e servir como uma linguagem de especificação para DPS; e 5) uma semântica variável
para uma linguagem de coordenação para simplificar a coordenação.This work was funded by FCT – Foundation for Science and Technology, the Portuguese Ministry of Science, Technology and Higher Education, through the Operational Programme for Human Capital (POCH). Grant reference: PD/BD/52238/201
TAaCT: Technology, Affect and Clinical Training
TAaCT is a project that examines contemporary medical training by attending to the long history of devices that have been used to train medical practitioners, which include texts, atlases, models and a range of audio-visual apparatus. The object of TAaCT is to include reflective thinking about how technologies of representation are used to engage directly with human feeling, but which a prevailing focus on technological progress toward realistic simulation has tended to marginalise
Methods for taking semantic graphs apart and putting them back together again
The thesis develops a competitive compositional semantic parser for Abstract Meaning Representation (AMR). This approach combines a neural model with mechanisms that echo ideas from compositional semantic construction in a new, simple dependency structure. The thesis first tackles the task of generating structured training data necessary for a compositional approach, by developing the linguistically motivated AM algebra. Encoding the terms over the AM algebra as dependency trees yields a simple semantic parsing model where neural tagging and dependency models predict interpretable, meaningful operations that construct the AMR.Diese Dissertation entwickelt einen kompositionellen semantischen Parser für den Graphformalismus Abstract Meaning Representation (AMR). Der Ansatz kombiniert ein neuronales Modell mit Mechanismen, die Ideen der klassischen kompositionellen semantischen Konstruktion widerspiegeln. Die Arbeit geht zunächst das Problem an, strukturierte latente Trainingsdaten zu erzeugen die für den kompositionellen Ansatz nötig sind. Für diesen Zweck wird die linguistisch motivierte AM Algebra entwickelt. Indem die Terme der AM Algebra als Dependenzbäume ausgedrückt werden, erhalten wir ein Modell für semantisches Parsen, in dem neuronale Tagging- und Dependenzmodelle interpretierbare, aussagekräftige Operationen vorhersagen die dann den AMR Graphen erzeugen. Damit erreicht das Modell starke Evaluationsergebnisse und deutliche Verbesserungen gegenüber einem weniger strukturierten Vergleichsmodell.DF
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