Thais Webber

• Computer Science PhD
• Lecturer in Computer Science at Aston University

Advancements in Medical Internet of Things (MIoT) technology ease remote health monitoring and effective management of medical devices. However, these developments also expose systems to novel cyber security risks as sophisticated threat actors exploit infrastructure vulnerabilities to access sensitive data or deploy malicious software, threatening...

Improving access to health information and territorial resources can be a way to help strengthen health-related quality of life perception in disadvantaged communities. We argue that, in countries facing diverse economic and social disparities and challenges, technology can be leveraged to improve communities' access to evidence-based, up-to-date,...

Endometriosis is a complex, poorly understood, female health condition that can markedly reduce a woman's quality of life. The gold-standard diagnostic method for Endometriosis is invasive laparoscopic surgery, which is costly, not timely, and comes with risks to the patient. We argue that the need for a non-invasive diagnosis procedure, higher qua...

With ever increasing amounts of travel, it is essential to have access to a patient’s medical data from different sources including many jurisdictions. The Serums project addresses this goal by creating a healthcare sharing system that places privacy and security aspects at the center. This raises significant challenges to both maintain privacy and...

The architectural design of a healthcare data sharing system must cope with security requirements especially when the system integrates different data sources and patient-centric features. The design choices come with different risks, where vulnerabilities and threats highly depend on how the system components interact and depend on each other to o...

This paper proposes a user-adaptable and personalized authentication paradigm for healthcare organizations, which anticipates to seamlessly reflect patients’ episodic and autobiographical memories to graphical and textual passwords aiming to improve the security strength of user-selected passwords and provide a positive user experience. We report o...

Advances in computer communication technology have enabled the rapid growth of e-health services for delivering healthcare, such as facilitating online consent and data sharing between patients and health professionals. Developing a patient-centric healthcare system is challenging because by necessity, it should be secure, reliable, and resilient t...

Healthcare data sharing platforms have been gaining prominence over the last decade, especially with the emergence of technologies dedicated to increase system security and users’ privacy. Moreover, these platforms are becoming less centralised as time progresses, with need for more data from a variety of locations and settings to be transferred be...

To facilitate personalised healthcare provision across Europe, we envision solutions that enable the secure integration and sharing of medical health records. These solutions should address privacy concerns, such as granular access control to personal data, establishing what should be accessible when and by whom, whilst complying with collective re...

Philanthropic hospitals in Brazil are in great part funded by the government and are daily accessed by a large portion of the population. As the Brazilian economy faces deep cuts in healthcare, managers are adjusting budgets and focusing on less expensive alternatives such as process improvements. Hospitals are even more impacted by the recent COVI...

Cancer pathway is the name given to a patient’s journey from initial suspicion of cancer through to a confirmed diagnosis and, if applicable, the definition of a treatment plan. Typically, a cancer patient will undergo a series of procedures, which we designate as events, during their cancer care. The initial stage of the pathway, from suspected di...

With an increasing trend in personalised healthcare provision across Europe, we need solutions to enable the secure transnational sharing of medical records, establishing granular access rights to personal patient data. Access rules can establish what should be accessible by whom for how long, and comply with collective regulatory frameworks, such...

The potential of healthcare systems worldwide is expanding as new medical devices and data sources are regularly presented to healthcare providers which could be used to personalise, improve and revise treatments further. However, there is presently a large gap between the data collected, the systems that store the data, and any ability to perform...

Philanthropic hospitals in Brazil are in great part-funded by the government and are daily accessed by a large part of the population. As the Brazilian economy faces deep cuts in healthcare, managers are forced to adjust budgets and invest more in process improvements. Hospitals are even more impacted by the recent COVID-19 pandemic with widespread...

Cancer pathway is the name given to a patient's journey from initial suspicion of cancer through to a confirmed diagnosis and, if applicable, the definition of a treatment plan. Typically, a cancer patient will undergo a series of procedures, which we designate as events, during their cancer care. The initial stage of the pathway, from suspected d...

There is a recognised move towards more personalised health with citizens at the centre of healthcare provision. In particular, there is an emphasis on the right of citizens to decide who, why, and when, should have access to their medical records. The EU project SERUMS is developing a tool-chain for the secure access of distributed medical informa...

Designing patient-centric healthcare systems which consider the smart integration of distributed medical data is challenging. This endeavour includes handling numerous architectural dependencies and requirements as a result of blending a variety of future generation technologies. Examples of recent approaches are proposals of unified format for med...

Systematic Literature Review is a widely adopted methodology to select relevant research in digital libraries using specific steps. Unlike a survey which is a comprehensive literature report on the body of works pertaining a eld, an SLR aims to select particular works according to pre-defined, specific criteria. In an SLR, relevant meta-data is ext...

This is an ongoing effort to define quantitative Performance Evaluation (PE), written to clarify the understanding of some concepts on terminology thus avoiding ambiguity in daily efforts when investigating systems characteristics. For a glossary of terms and definitions provided by standard bodies, it is highly suggested to peruse information offe...

Modelling and Simulation are inexpensive and computationally efficient manners to analyze virtually any system. The technique has attracted the attention of cross-disciplinary practitioners due to easiness when abstracting systems to models and its fast and reliable solution mechanisms for assessing performance. The present work discusses a metamod...

We propose an educational framework to combine different disciplines such as Software Engineering, Operating Systems, and Simulation to teach project management, modular programming, and system decomposition to students. We present guidelines for the framework implementation and insights as to how plan simulations of virtualized operating systems....

The choice of virtualized solutions (e.g. the use of virtual machines over physical machines) for systems execution under different contexts is a commonly used approached for several domain applications. The possibility to abstract entire platforms, infrastructures, or software as a service has become a valid technique for application execution usi...

The present paper addresses the transformation of modeling primitives in structured Markovian based formalisms such as Queueing Networks, Stochastic Petri Nets, Performance Evaluation Process Algebra, and Stochastic Automata Networks. Since all of those formalisms share the same underneath Markov Chain, there is a formal correspondence that yields...

This is a model that should be opened by the Decisor tool - download it at https://github.com/czekster/Decisor/releases

This is a model that should be opened by the Decisor tool - download it at https://github.com/czekster/Decisor/releases

The applications requirements are becoming more rigorous, demanding the execution of concurrent tasks that must also take into account modularity and flexibility. A fundamental part of the operating system development concerns the implementation of scheduling algorithms. In an embedded system context, it is essential to consider the scheduling algo...

Selecting ERP (Enterprise Resource Planning) software is crucial to enhance productivity because it provides high-quality services for end users. The choice of an ERP is a problem that should undertake deeper scrutiny. For example, several criteria are usually present , having different tradeoffs. Analysts and managers, when deciding which ERP to a...

Addressing consistent and reliable decision making are crucial activities when choosing seemingly related alternatives for a set of criteria. Models and methods for aiding decisions such as Analytic Hierarchy Process (AHP) were developed to handle quantified assessments of quality attributes, usually intangible and numerically hard to cope. We intr...

There is an unquestionable need to improve healthcare processes across all levels of care in order to optimise the use of resources whilst guaranteeing high quality care to patients. However, healthcare processes are generally very complex and have to be fully understood before enhancement suggestions can be made. Modelling with widely used notatio...

Blending curved and straight lines on angular modes are proposed for intra‐frame prediction in high‐efficiency video coding (HEVC). All 33 angular modes in HEVC have received an offset‐based displacement calculation to each predicted sample, so that the resulting prediction block models image regions with curved textures. The proposal includes a ne...

Este artigo foca na análise do processo de faturamento de contas hospitalares de internação, em uma investigação que combina os temas gestão de processos de negócio (BPM) e simulação de eventos discretos (DES) para apoiar iniciativas de melhorias em processos de negócio em hospitais filantrópicos. Para condução da fase de mapeamento utilizou-se a n...

This is the presentation for DataMod 2018 conference held at Toulouse, France on June/2018.

Delay or Disruption Tolerant Networks (DTN) are characterized by long delays and intermittent connectivity, requiring efficient energy consumption for increasing the mobile nodes lifetime. The movements of nodes modify the network topology, changing the number of connection opportunities between nodes. This paper proposes a new technique for energy...

Healthcare involves complex decision making from planning to resource management. Resources in hospitals are usually allocated by experienced managers, however, due to an inherent process complexity, decisions are surrounded by uncertainties, variabilities, and constraints. Information Systems must be robust enough to provide support to stakeholder...

A complex application implemented as a System-on-Chip (SoC) demands extensive system level modeling. Its implementation encompasses a large number of cores and an advanced interconnection scheme such as a Network-on-Chip (NoC). This type of application normally requires energy efficiency and execution time minimization, which implies high-level exp...

Measuring productivity in globally distributed projects is crucial to improve team performance. These measures often display information on whether a given project is moving forward or starts to demonstrate undesired behaviors. In this paper we are interested in showing how analytical models could deliver insights for the behavior of specific distr...

Nowadays, security concerns are becoming extremely important as attacks and intrusions to systems and computers networks increase significantly. Different measures and countermeasures are employed to guarantee server security as well as new techniques and tools. Intrusion Detection Systems (IDSs) are expert software broadly used by system administr...

Network-on-Chip (NoC) is a power architecture that emerged to solve communication issues present in modern Systems-on-Chip (SoCs). NoC based architectures are very scalable and offer high levels of communication parallelism, among other features. Every efficient NoC implementation requires several design steps to accomplish indices of performance....

A virtualização através do uso de máquinas virtuais sobre máquinas físicas, para executar diferentes sistemas em diferentes domínios de aplicação tem sido uma abordagem comumente adotada em diferentes contextos. A possibilidade de se abstrair plataformas, infraestrutura ou software como um serviço passou a ser uma técnica válida para executar siste...

A escolha de soluções virtualizadas para executar diferentes sistemas em diferentes contextos tem sido uma abordagem comumente adotada para uma gama de aplicações. O uso de ambientes virtualizados é relevante e crucial, entretanto, em muitos casos estas tecnologias são escolhidas sem verificação prévia de desempenho ou outros atributos não funciona...

A escolha de soluções virtualizadas para executar diferentes sistemas em diferentes contextos tem sido uma abordagem comumente adotada para uma gama de aplicações. O uso de ambientes virtualizados é relevante e crucial, entretanto, em muitos casos estas tecnologias são escolhidas sem verificação prévia de desempenho ou outros atributos não funciona...

Each new production technology of integrated circuit (IC) drives more transistors area reduction, implying smaller and denser circuits. This scenario allows integrating several Processing Elements (PEs) into the same IC with efficient communication architecture such as the scalable topologies of Network on Chip (NoC). However, these newer productio...

Multiprocessor System-on-Chip (MPSoC) based on Network-on-Chip (NoC) integrates a large amount of Processor Elements (PEs) to fulfill the performance requirements of several applications. These applications are composed of a set of intercommunicating tasks, which are dynamically mapped onto PEs of the target architecture. However, the efficient tas...

This paper discusses the impact of routing arbitration mechanism on the packet latency for 3D NoC (Three-dimensional Network-on-Chip) architectures. We implemented several variations of Round-Robin mechanisms to explore how the arbitration efficiency affects the packet latency. The underlying objective is to discuss the compromise of increase route...

The overall system-on-chip performance depends on the network architecture, whose communication latency significantly impacts on the application performance. The challenge for on-chip networks is reducing costs while providing high performance such as low latency and high throughput. One alternative to achieve such goals is to implement efficient r...

Complex systems on chip containing dozens of processing resources with critical communication requirements usually rely on the use of networks on chip (NoCs) as communication infrastructure. NoCs provide significant advantages over simpler infrastructures such as shared busses or point to point communication, including higher scalability, more effi...

Networks-on-chip (NoCs) are already a common choice of communication infrastructure for complex systems-on-chip (SoCs) containing a large number of processing resources and with critical communication requirements. A NoC provides several advantages, such as higher scalability, efficient energy management, higher bandwidth and lower average latency,...

Poster presentation with the results of our research regarding the development of better techniques for parallelization of nbody codes on multicore hardware architectures during the Symposium Humboldt Kolleg 2014, "Science and Method: Paradigms and perspectives" in Porto Alegre, RS, Brazil.

Tiny is a scalable and efficient three-dimensional (3D) network-on-chip (NoC) designed to reduce latency and area. A theoretical analysis demonstrates its efficiency when compared with a basic 3D mesh NoC. Mapping independent traffics with different injection rates makes the trade-offs analysis of Tiny possible. Results highlight that Tiny always r...

A Multiprocessor System-on-Chip (MPSoC) composed of different types of processors is known as heterogeneous MPSoC. This kind of MPSoC based on Network-on-Chip (NoC) is a promising target architecture to fulfill requirements of high processing and communicating rate, enabling the execution of several tasks at the same time. Among the challenges in c...

This paper presents Tiny NoC, which is a scalable and efficient 3D mesh architecture developed to minimize latency and NoC area. First, we show a theoretical analysis of latency and area occupancy to demonstrate Tiny NoC efficiency when compared to a basic mesh NoC. Then, we select a set of synthetic and mapping independent traffic with several inj...

Advances in design integration have enabled the integration of large Multiprocessor Systems-on-Chip (MPSoC). Such systems are prone to the execution of complex applications if high degree of parallelism is employed on the communication infrastructure. Network-on-Chip (NoC) has emerged as a new communication paradigm for large MPSoCs with advantages...

The emergence of wireless networks has contributed to a growing number of studies and protocols regarding its performance and reliability requirements, among others. Several issues have to be considered when deploying such devices under harsh environmental conditions. These issues often force the designer to adopt decisions that are usually difficu...

The advances in deep submicron technology have made the development of large Multiprocessor Systems-on-Chip (MPSoC) possible and Networks-on-Chip (NoCs) have been recognized to provide an efficient communication architecture for such systems. With the positive effects on the device's integration some drawbacks arise, such as the increase of fault s...

Communication plays a crucial role in the design of high performance Multiprocessor Systems-on-Chip (MPSoC). Accordingly, Networks-on-Chip (NoC) have been successfully employed as a solution to deal with communication in complex MPSoCs. NoC-based architectures are characterized by various tradeoffs related to structural characteristics, performance...

Several new applications have high complexity degree, requiring high processing rate and memory usage. Multiprocessor System-on-Chip (MPSoC) is a promising architecture to fulfill these requirements, due to its high parallelism that enables several tasks been executed at the same time. One problem in current heterogeneous MPSoC design is applicatio...

This paper proposes an architectural improvement for the Modbus RTU protocol to integrate equipments in industrial automation networks, employing hybrid communication with wired Modbus RTU and wireless IEEE 802.15.4. These environments have different electromagnetic interferences, requiring protocols with noise immunity to varied equipments such as...

3D NoC-based architectures have emerged to reduce the network latency, the energy consumption and total area in comparison to 2D NoC topologies. However, they are characterized by various trade-offs with regard to the three dimensional structure and its performance specifications. In this paper, we present a 3D NoC mesh architecture called Lasio, w...

NoC has emerged as as efficient communication infrastructure to fulfill the heavy communication requirements of several applications, which are implemented on MPSoC target architectures. 2D NoCs are natural choices of communication infrastructure for the majority of actual chip fabrication technologies. However, wire delay and power consumption are...

Numerical analysis of Markovian models is relevant for performance evaluation and probabilistic analysis of systems’ behavior from several fields in science and engineering. These models can be represented in a compact fashion using Kronecker algebra. The Vector-Descriptor Product (VDP) is the key operation to obtain stationary and transient soluti...

Avaliar o desempenho de sistemas é um ponto-chave para detectar gargalos de execução, possíveis otimizações e, sobretudo para prover aplicações com alto grau de confiabilidade e desempenho. Muitas são as formas para se avaliar o desempenho de sistemas, por exemplo,monitoração, medições, simulações e modelagem analítica. Muitas vezes, não se dispõe...

The description of large state spaces through stochastic structured modeling formalisms like stochastic Petri nets, stochastic automata networks and performance evaluation process algebra usually represent the infinitesimal generator of the underlying Markov chain as a Kronecker descriptor instead of a single large sparse matrix. The best known alg...

Stochastic modeling of globally distributed projects has become a way to evaluate the performance of teams working in different time zones. The interest in extracting and analyzing quantitative data from geographically dispersed teams has grown throughout the years as major development companies were attracted by potential benefits. We direct our a...

Software development projects have become a challenge for both industry and academia regarding the performance evaluation of teams. Recently, a Stochastic Automata Networks (SAN) model was proposed as theoretical representation for performance prediction of software development teams. In this paper, we present an exercise of such SAN analytical mod...

Service Level Agreements (SLAs) are used to guarantee quality of service (QoS) between customers and service providers. In an SLA, parties establish a common set of rules and responsibilities. In this paper we propose a practical stochastic modeling of a multi-tier architecture considering SLAs for specific transactions. The model is parameterized...

Structured Markovian formalisms have emerged to facilitate the re-presentation of large state spaces and transitions. However, structuring intro-duces algorithmic challenges, such as detection of reachable states, as well as specialized numerical solutions. Recent researches have proposed the use of Multi-valued Decision Diagrams (MDD) for the comp...

The solution of Markovian models is usually non-trivial to be performed using iterative methods, so it is well-fitted to simulation approaches and high performance implementations. The Bootstrap simulation method is a novel simulation technique of Markovian models that brings a considerable improvement in the results accuracy, notwithstanding its h...

The analytical solution of large Markovian models is one of the major challenges in performance evaluation. Structured formalisms provide a modular description to tackle state space explosion by presenting memory-efficient solutions based on tensor algebra and specific software tools implement such solutions using iterative methods. However, even t...

The solution of state-based stochastic models is usually a demanding application, then it is a natural subject to high performance techniques. We are particularly interested in the speedup of Bootstrap Simulation of structured Markovian models. This approach is a quite recent development in the performance evaluation area, and it brings a considera...

Numerical analysis of Markovian models is relevant for performance evaluation and probabilistic analysis of systems' behavior from several fields such as Bioinformatics, Economics, and Engineering. These models can be represented in a compact fashion using Kronecker algebra. The Vector-Descriptor Product is the key operation to obtain stationary so...

Global software engineering is an area of increasing research challenges, in which teams are dispersed in multiple sites collaborating across borders and time zones. In spite of its potential competitive advantages, globally distributed projects must deal with difficulties when distributing resources such as teams with cultural diversities, differe...

The key operation to obtain stationary and transient solutions of transition systems described by Kronecker structured formalisms is the Vector-Descriptor product. This operation is usually performed with shuffling operations and matrices aggregations to reduce the floating point multiplications inside iterative methods. Due to the flexibility of t...

Simulation is an interesting alternative to solve Markovian models. However, when compared to analytical and numerical solutions it suffers from a lack of precision in the results due to the very nature of simulation, which is the choice of samples through pseudorandom generation. This paper proposes a different way to simulate Markovian models by...

This paper presents a software package, called GTAexpress, to handle structured continuous-time Markovian models expressed using generalized tensor algebra, also known as, Kronecker descriptors. The proposed software package has the most advanced methods to provide stationary and transient solutions as well as some basic structural properties of mo...

The solution of continuous and discrete-time Markovian models is still challenging mainly when we model large complex systems, for example, to obtain performance indexes of parallel and distributed systems. However, iterative numerical algorithms, even well-fitted to a multidimensional structured representation of Markov chains, still face the stat...

Many Markovian stochastic structured modeling formalisms like Petri nets, automata networks and process algebra represent the in- finitesimal generator of the underlying Markov chain as a descrip- tor instead of a traditional sparse matrix. A descriptor is a com- pact and structured storage based on a sum of tensor (Kronecker) products of small mat...

Modeling large complex systems always requires a structured description. The state space explosion itself exists only because we can describe a very large system, i.e., a system with a huge state space, by describing a structure simple enough to be understood by us, humans. Therefore, it is admissible to rely on a structured description to all prob...

New guidelines and methods for teams and organizational structures are crucial to improve efficiency and scalability for globally distributed software development. Our work introduces a simplified process to be used by local teams working globally. The process is derived from the Agile Unified Process proposal and is highly centered in team motivat...

The key operation to obtain stationary and transient solutions of models de- scribed by Kronecker structured formalisms using iterative methods is the Vector- Descriptor product. This operation is usually performed with the Shuffle algo- rithm, which was proposed to Stochastic Automata Networks, but it is also cur- rently used by Stochastic Petri N...

This paper presents a theoretical performance analysis of a parallel implementation of a tool called Performance Evaluation for Parallel Systems (PEPS). This software tool is used to analyze Stochastic Automata Networks (SAN) models. In its sequential version, the execution time becomes impracticable when analyzing large SAN models. A parallel vers...

This paper presents a framework to decompose a single GSPN model into a set of small interacting models. This decomposition tech- nique can be applied to any GSPN model with a nite set of tangible markings and a generalized tensor algebra (Kronecker) representation can be produced automatically. The numerical impact of all the possi- ble decomposit...

The Stochastic Automata Networks (SAN) formalism provides a compact and modular description for Marko-vian models. Moreover, SAN is suitable to derive perfor-mance indices for systems analysis and interpretation using iterative numerical solutions based on a descriptor and a state space sized probability vector. Depending on the size of the model t...

Kronecker descriptors are an efficient option to store the underlying Markov chain of a model in a structured and compact fashion. The basis of classical numerical solutions for Kronecker descriptors represented models is the Vector-Descriptor Product (VDP). The Shuffle algorithm is the most popular VDP method to handle generalized descriptors, i.e...

This paper presents the parallelization of a self-verified method for solving dense linear equations. Verified computing provides an interval result that surely contains the correct result. The advent of parallel computing and its impact in the overall performance of various algorithms on numerical analysis have been increasing in the last decade....