Kyller Costa Gorgônio

Automatic timed automata extraction from ladder programs for model-based analysis of control systems

Control systems are used to produce a certain result with little or no human supervision. The principal aim of such systems is to ensure that resources are used efficiently and that the desired product quality is achieved. Moreover, for critical systems such as oil and gas plants, it is important to guarantee the safety and reliability of the operation. Therefore, it is necessary to verify whether what is running in the device is in accordance with what was defined in the specification documents. The goal of this work is to present a method that automatically generates the timed automata models from the specification ISA 5.2 Binary Logic Diagrams, and the implementation Ladder programs, for model-based analysis, in order to increase the dependability in the behavior of critical control systems. This approach is based on the use of the Uppaal tool and the Uppaal-TRON testing tool.

On the automatic generation of timed automata models from ISA 5.2 diagrams

Safety Instrumented Systems (SIS) are usually designed to prevent accidents, avoid undesirable situations and guarantee continuous operation of oil and gas production systems. An interruption in the operation can be caused by faults in sensors and/or actuators. Hence, SIS are usually integrated to the supervisory control system in order to use the information from sensors to prevent such undesirable situations. In this scenario, it is important to be able to validate the SIS implementation against its specification in order to increase the reliability of the system. In this work a technique to improve the dependability of SIS is introduced. A method to obtain a timed automata from a ISA 5.2 specification is presented and applied to a case study provided by Petrobras (Brazilian oil company). Finally, an approach to perform automatic testing of the implementation using the generated model is discussed. The method introduced here is based on the use of the Uppaal model checker and the Uppaal-TRON testing tool.

A Bayesian network approach to assist on the interpretation of software metrics

Despite the quantity of software metrics that has been proposed, their adoption and application by practitioners has been limited. A challenge to their use is to interpret them to perform assessments and predictions. The existing approaches to assist with their interpretation consists of defining thresholds to determine whether the value of a metric is acceptable. These approaches are not enough to ensure a correct metrics interpretation, because they ignore risks and other subjective factors that influence the measurement process. This might affect the metrics interpretation, and consequently, the managers decision. To minimize wrong decisions based on software metrics, we present a method to construct Bayesian networks to assist on metric interpretation considering these risks. We successfully validated the method with a case study performed in three software development projects. We concluded that it is a promising approach to assist practitioners to interpret metrics and support software projects managerial decision-making.

A compositional method for the synthesis of asynchronous communication mechanisms

Asynchronous data communication mechanisms (ACMs) have been extensively studied as data connectors between independently timed concurrent processes. In previous work, an automatic ACM synthesis method based on the generation of the reachability graph and the theory of regions was proposed. In this paper, we propose a new synthesis method based on the composition of Petri net modules, avoiding the exploration of the reachability graph. The behavior of ACMs is formally defined and correctness properties are specified in CTL. Model checking is used to verify the correctness of the Petri net models. The algorithms to generate the Petri net models are presented. Finally, a method to automatically generate C++ source code from the Petri net model is described.

Assisting the continuous improvement of Scrum projects using metrics and Bayesian networks.

Scrum is a simple process to understand, but hard to adopt. Therefore, there is a need for resources to assist on its adoption. In this paper, we present the process followed to build a Bayesian network to assist on the assessment of the quality of the software process in the context of Scrum projects. The model provides data to help Scrum Masters lead the improvement of business value delivery of Scrum teams. The process is divided into 2 phases. In the first phase, we built the Bayesian network based on expert knowledge extracted from the literature and experts. We used a top‐down approach and reasoning to define the key metrics necessary to build the models and their relationships. In the second phase, we updated the Bayesian network based on limitations of the first version. We validated the Bayesian network inferences with 10 simulated scenarios. Comparing both versions, for all scenarios, we improved the accuracy of the inferences. Therefore, we concluded that the Bayesian networks adequately represent Scrum projects from the viewpoint of the Scrum Master. Finally, the model built is in conformance with agile methods tailoring and can be adapted to any Scrum team.

A Standard-Based and Context-Aware Architecture for Personal Healthcare Smart Gateways

The rising availability of Personal Health Devices (PHDs) capable of Personal Network Area (PAN) communication and the desire of keeping a high quality of life are the ingredients of the Connected Health vision. In parallel, a growing number of personal and portable devices, like smartphones and tablet computers, are becoming capable of taking the role of health gateway, that is, a data collector for the sensor PHDs. However, as the number of PHDs increase, the number of other peripherals connected in PAN also increases. Therefore, PHDs are now competing for medium access with other devices, decreasing the Quality of Service (QoS) of health applications in the PAN. In this article we present a reference architecture to prioritize PHD connections based on their state and requirements, creating a healthcare Smart Gateway. Healthcare context information is extracted by observing the traffic through the gateway. A standard-based approach was used to identify health traffic based on ISO/IEEE 11073 family of standards. A reference implementation was developed showing the relevance of the problem and how the proposed architecture can assist in the prioritization. The reference Smart Gateway solution was integrated with a Connected Health System for the Internet of Things, validating its use in a real case scenario.

Generalized connections and incentives for supporting CE devices in live streaming systems

In the modern web applications, users have assumed a prominent role by effectively contributing to the provision of some online services, such as live streaming of multimedia content. For instance, while users watch a football match or a concert through those applications, their devices may also be sharing the received content with others who are interested in the same event, defining a Peer-to-Peer (P2P) service model. The state of the art solutions for this purpose are highly dependent on the end-points and the available network bandwidth, hindering the use of some devices (e.g. phone, tablets, TVs, etc.). In this context, the Global Media Transmission Protocol (GMTP) is proposed, a cross-layer network/transport protocol that uses access routers as the end-point of a system-independent P2P network and to cache contents of servers in Content Delivery Networks (CDN). It is discussed how GMTP enables users of a variety of smart consumer electronic devices to use GMTP-based systems, as well as a technique for encouraging users to share their network resources according to the principle that the more a users router shares bandwidth, the more incentives a users router will receive from the network. The evaluation results show that GMTP can reduce the startup delay in mobile devices, while scaling the number of nodes without increasing the bandwidth consumption, independent of the device type.

An Algorithm to Define the Node Probability Functions of Bayesian Networks based on Ranked Nodes

Bayesian Network (BN) has been used in a broad range of applications. A challenge in constructing a BN is defining the node probability tables (NPTs), which can be learned from data or elicited from domain experts. In practice, it is common to not have enough data for learning and elicitation from experts is the only option. However, the complexity of defining NPTs grows exponentially, making their elicitation process costly and error-prone. Previous work proposed a solution: the ranked nodes method (RNM). However, the details necessary to implement it were not presented. Nowadays, the solution is only available through a commercial tool. Hence, this paper presents an algorithm to define NPT using the RNM. We include details regarding sampling and how to mix truncated Normal distributions and convert the resulting distribution into an NPT. We compared the results calculated using our algorithm with the commercial tool through an experiment. The results show that our solution is equivalent to the commercial tools’ in terms of NPT definition with a mean difference of 1.6%. Furthermore, our solution is faster. The solution developed is made available as open source software. Bayesian Network; Expert systems; Node Probability Table; Ranked nodes

Petri Nets for Component-Based Software Systems Development

The Software Engineering discipline was created to try to apply techniques and methods of others engineering disciplines to software systems development. To achieve this goal it was necessary to change the way software was developed, not only at code level, but also at the process level. Like in other engineering disciplines, one of the major objectives of software engineering is to develop artifacts in a systematic way. Several building block approaches were proposed and developed along the years. Nowadays one of the most researched and used approach are software components (Crnkovic and Grunske, 2007. Nierstrasz et al., 2002). Components are autonomous units with independent life cycle that represent an specific functionality. A component consists of functionality, interface and possibly other non functional characteristics. The development of bigger systems with components as building blocks is called Component Based Development (CBD). To make this possible it is necessary to adapt the traditional software engineering techniques and methods, or even defined new ones, to attend to specific CBD requirements. In the context of Component Based Software Engineering (CBSE) the objective is to define a set of practices that promotes the CBD. Formal methods improve the development process of software and hardware systems by helping designers to achieve dependability at different levels of abstractions such as requirements, specification, modeling and design. This is mainly due to the fact that the application of formal methods helps discovering and removing errors by performing automatic analysis and verification (Clarke and Wing, 1996). Petri nets (Murata, 1989), and more specifically Hierarchical Coloured Petri Nets (HCPN) (Jensen, 1992. Jensen, 1997) are a very powerful tool that has been widely studied and applied for the specification and analysis of complex concurrent systems (Donatelli and Thiagarajan, 2006. Kleijn and Yakovlev, 2007. Jensen, 2005. Jensen, 2006). It has a graphical representation that helps the design of complex software systems. There are several advantages of using a formal method in systems design such as, automatic simulation, proof of properties and unambiguous documentation. In the context of software engineering, the reuse of artifacts in the development of new software systems increases the productivity. Also, the reuse of artifacts that are well known to be correct is an effective way to increase the dependability on the system under development. Reuse is not restricted to pieces of source code, but it can be also be applied to