Simulation-based testing of highly configurable cyber-physical systems: automation, optimization and debugging

Sistema Ziber-Fisikoek sistema ziber digitalak sistema fisikoekin uztartzen dituzte. Sistema hauen aldakortasuna handitzen ari da erabiltzaileen hainbat behar betetzeko. Ondorioz, sistema ziber-fisikoa aldakorrak edota produktu lerroak ari dira garatzen eta sistema hauek milaka edo milioika konfiguraziotan konfiguratu daitezke. Sistema ziber-fisiko aldakorren test eta balidazioa prozesua garestia da, batez ere probatu beharreko konfigurazio kopuruaren ondorioz. Konfigurazio kopuru altuak sistemaren prototipo bat erabiltzea ezinezkoa egiten du. Horregatik, sistema ziber-fisiko aldagarriak simulazio modeloak erabilita probatzen dira. Hala ere, simulazio bidez sistema ziber-fisikoak probatzea erronka izaten jarraitzen du. Hasteko, simulazio denbora altua izaten da normalki, software-az aparte, sistema fisikoa simulatu behar delako. Sistema fisiko hau normalean modelo matematiko konplexuen bitartez modelatzen da, konputazionalki garestia delarik. Jarraitzeko, sistema ziber-fisikoek ingeniaritzaren domeinu ezberdinak dituzte tartean, adibidez mekanika edo elektronika. Domeinu bakoitzak bere simulazio erremienta erabiltzen du, eta erremienta guzti hauek interkonektatzeko ko-simulazioa erabiltzen da. Nahiz eta ko-simulazioa abantaila bat izan ematen duen flexibilitateagatik, simulagailu ezberdinen erabilerak simulazio denbora handiagotzen du. Azkenik, sistema ziber-fisikoak simulaziopean probatzean, probak maila ezberdinetan egin behar dira (adb., Model, Software eta Hardware-in-the-Loop mailak), eta honek, proba-kasuak exekutatzeko denbora handitzen du. Tesi honen helburua sistema ziber-fisiko aldakorren test jardunbideak hobetzea da, horretarako automatizazio, optimizazio eta arazketa metodoak proposatzen ditu. Automatizazioari dagokionez, lehenengo, erremienta-bidezko metodologia bat proposatzen da. Metodologia hau test sistema instantziak automatikoki sortzeko gai da, test sistema hauek sistema ziber-fisiko aldagarrien konfigurazioak automatikoki probatzeko gai dira (adb., test orakuluen bitartez). Bigarren, test frogak automatikoki sortzeko planteamendu bat proposatzen da helburu anitzeko bilaketa algoritmoak erabilita. Optimizazioari dagokionez, test frogen aukeraketarako planteamendu bat eta test frogen priorizaziorako beste planteamendu bat proposatzen dira, biak bilaketa alix goritmoak erabiliz, sistema ziber-fisiko aldakorrak test maila ezberdinetan probatzeko helburuarekin. Arazketari dagokionez, “espektroan oinarritutako falten lokalizazioa” izeneko teknika bat produktu lerroen testuingurura adaptatu da, eta faltak isolatzeko metodo bat proposatzen da. Honek, falta ezberdinak lokalizatzea errezten du ez bakarrik sistema ziber-fisiko aldakorretan, baizik eta edozein produktu lerrotan non “feature model” delako modeloak erabiltzen diren aldakortasuna kudeatzeko.Los sistemas cyber-físicos (CPSs) integran tecnologías digitales con procesos físicos. La variabilidad de estos sistemas está creciendo para responder a la demanda de diferentes clientes. Como consecuencia de ello, los CPSs están volviéndose configurables e incluso líneas de producto, lo que significa que pueden ser configurados en miles y millones de configuraciones. El testeo de sistemas cyber-físicos configurables es un proceso costoso, en general debido a la cantidad de configuraciones que han de ser testeadas. El número de configuraciones a testear hace imposible el uso de un prototipo del sistema. Por ello, los sistemas CPSs configurables están siendo testeadas utilizando modelos de simulación. Sin embargo, el testeo de sistemas cyber-físicos bajo simulación sigue siendo un reto. Primero, el tiempo de simulación es normalmente largo, ya que, además del software, la capa física del CPS ha de ser testeada. Esta capa física es típicamente modelada con modelos matemáticos complejos, lo cual es computacionalmente caro. Segundo, los sistemas cyber-físicos implican el uso de diferentes dominios de la ingeniería, como por ejemplo la mecánica o la electrónica. Por ello, para interconectar diferentes herramientas de modelado y simulación hace falta el uso de la co-simulación. A pesar de que la co-simulación es una ventaja en términos de flexibilidad para los ingenieros, el uso de diferentes simuladores hace que el tiempo de simulación sea más largo. Por último, al testear sistemas cyberfísicos haciendo uso de simulación, existen diferentes niveles (p.ej., Model, Software y Hardware-in-the-Loop), lo cual incrementa el tiempo para ejecutar casos de test. Esta tesis tiene como objetivo avanzar en la práctica actual del testeo de sistemas cyber-físicos configurables, proponiendo métodos para la automatización, optimización y depuración. En cuanto a la automatización, primero, se propone una metodología soportada por una herramienta para generar automáticamente instancias de sistemas de test que permiten testear automáticamente configuraciones del sistema CPS configurable (p.ej., haciendo uso de oráculos de test). Segundo, se propone un enfoque para generación de casos de test basado en algoritmos de búsqueda multiobjetivo, los cuales generan un conjunto de casos de test. En cuanto a la optimización, se propone un enfoque para selección y otro para priorización de casos de test, ambos basados en algoritmos de búsqueda, de cara a testear eficientemente sistemas cyberfísicos configurables en diferentes niveles de test. En cuanto a la depuración, se adapta una técnica llamada “Localización de Fallos Basada en Espectro” al contexto de líneas de productos y proponemos un método de aislamiento de fallos. Esto permite localizar bugs no solo en sistemas cyber-físicos configurables sino también en cualquier línea de producto donde se utilicen modelos de características para gestionar la variabilidad.Cyber-Physical Systems (CPSs) integrate digital cyber technologies with physical processes. The variability of these systems is increasing in order to give solution to the different customers demands. As a result, CPSs are becoming configurable or even product lines, which means that they can be set into thousands or millions of configurations. Testing configurable CPSs is a time consuming process, mainly due to the large amount of configurations that need to be tested. The large amount of configurations that need to be tested makes it infeasible to use a prototype of the system. As a result, configurable CPSs are being tested using simulation. However, testing CPSs under simulation is still challenging. First, the simulation time is usually long, since apart of the software, the physical layer needs to be simulated. This physical layer is typically modeled with complex mathematical models, which is computationally very costly. Second, CPSs involve different domains, such as, mechanical and electrical. Engineers of different domains typically employ different tools for modeling their subsystems. As a result, co-simulation is being employed to interconnect different modeling and simulation tools. Despite co-simulation being an advantage in terms of engineers flexibility, the use of different simulation tools makes the simulation time longer. Lastly, when testing CPSs employing simulation, different test levels exist (i.e., Model, Software and Hardware-in-the-Loop), what increases the time for executing test cases. This thesis aims at advancing the current practice on testing configurable CPSs by proposing methods for automation, optimization and debugging. Regarding automation, first, we propose a tool supported methodology to automatically generate test system instances that permit automatically testing configurations of the configurable CPS (e.g., by employing test oracles). Second, we propose a test case generation approach based on multi-objective search algorithms that generate cost-effective test suites. As for optimization, we propose a test case selection and a test case prioritization approach, both of them based on search algorithms, to cost-effectively test configurable CPSs at different test levels. Regarding debugging, we adapt a technique named Spectrum-Based Fault Localization to the product line engineering context and propose a fault isolation method. This permits localizing bugs not only in configurable CPSs but also in any product line where feature models are employed to model variability

Automated Misconfiguration Repair of Configurable Cyber-Physical Systems with Search: an Industrial Case Study on Elevator Dispatching Algorithms

Real-world Cyber-Physical Systems (CPSs) are usually configurable. Through parameters, it is possible to configure, select or unselect different system functionalities. While this provides high flexibility, it also becomes a source for failures due to misconfigurations. The large number of parameters these systems have and the long test execution time in this context due to the use of simulation-based testing make the manual repair process a cumbersome activity. Subsequently, in this context, automated repairing methods are paramount. In this paper, we propose an approach to automatically repair CPSs' misconfigurations. Our approach is evaluated with an industrial CPS case study from the elevation domain. Experiments with a real building and data obtained from operation suggests that our approach outperforms a baseline algorithm as well as the state of the practice (i.e., manual repair carried out by domain experts).Comment: To be published in the 45th International Conference on Software Engineering, SEIP trac

Applying and Extending the Delta Debugging Algorithm for Elevator Dispatching Algorithms (Experience Paper)

Elevator systems are one kind of Cyber-Physical Systems (CPSs), and as such, test cases are usually complex and long in time. This is mainly because realistic test scenarios are employed (e.g., for testing elevator dispatching algorithms, typically a full day of passengers traveling through a system of elevators is used). However, in such a context, when needing to reproduce a failure, it is of high benefit to provide the minimal test input to the software developers. This way, analyzing and trying to localize the root-cause of the failure is easier and more agile. Delta debugging has been found to be an efficient technique to reduce failure-inducing test inputs. In this paper, we enhance this technique by first monitoring the environment at which the CPS operates as well as its physical states. With the monitored information, we search for stable states of the CPS during the execution of the simulation. In a second step, we use such identified stable states to help the delta debugging algorithm isolate the failure-inducing test inputs more efficiently. We report our experience of applying our approach into an industrial elevator dispatching algorithm. An empirical evaluation carried out with real operational data from a real installation of elevators suggests that the proposed environment-wise delta debugging algorithm is between 1.3 to 1.8 times faster than the traditional delta debugging, while producing a larger reduction in the failure-inducing test inputs. The results provided by the different implemented delta debugging algorithm versions are qualitatively assessed with domain experts. This assessment provides new insights and lessons learned, such as, potential applications of the delta debugging algorithm beyond debugging

QoS-aware Metamorphic Testing: An Elevation Case Study

Elevators are among the oldest and most widespread transportation systems, yet their complexity increases rapidly to satisfy customization demands and to meet quality of service requirements. Verification and validation tasks in this context are costly, since they rely on the manual intervention of domain experts at some points of the process. This is mainly due to the difficulty to assess whether the elevators behave as expected in the different test scenarios, the so-called test oracle problem. Metamorphic testing is a thriving testing technique that alleviates the oracle problem by reasoning on the relations among multiple executions of the system under test, the so-called metamorphic relations. In this practical experience paper, we report on the application of metamorphic testing to verify an industrial elevator dispatcher. Together with domain experts from the elevation sector, we defined multiple metamorphic relations that consider domain-specific quality of service measures. Evaluation results with seeded faults show that the approach is effective at detecting faults automatically

Innovation and creativity and the Spanish White Paper on Communication Degrees: adapting universities to a changing media landscape

Many universities are trying to adapt their curricula to the changing media landscape. Innovation and creativity are considered key concepts in this new context, as can be shown by the Innovation Journalism initiative developed at Stanford University and some other that can be used to promote both innovation and creativity in Media Studies (such as Design Thinking and Creation Nets). In addition to reporting on these trends, this paper describes how the official Spanish White Paper on Communication Degreees deals with both innovation and creativity, analyzing the presence of these two concepts in the curricula proposed within it.Muchas universidades están tratando de adaptar sus planes de estudio a la evolución del panorama mediático. La innovación y la creatividad son consideradas clave en este nuevo contexto, como lo demuestran tendencias como Innovation Journalism (desarrollada en la Universidad de Stanford) y métodos que se pueden utilizar para promover la innovación y la creatividad en los estudios de Comunicación (tales como Design Thinking y Creation Nets). Este artículo da cuenta de estas nuevas tendencias y describe asimismo la presencia de la innovación y la creatividad en los currículos propuestos en el Libro Blanco de los títulos de Grado en Comunicación

Towards a Taxonomy for Eliciting Design-Operation Continuum Requirements of Cyber-Physical Systems

Software systems that are embedded in autonomous Cyber-Physical Systems (CPSs) usually have a large life-cycle, both during its development and in maintenance. This software evolves during its life-cycle in order to incorporate new requirements, bug fixes, and to deal with hardware obsolescence. The current process for developing and maintaining this software is very fragmented, which makes developing new software versions and deploying them in the CPSs extremely expensive. In other domains, such as web engineering, the phases of development and operation are tightly connected, making it possible to easily perform software updates of the system, and to obtain operational data that can be analyzed by engineers at development time. However, in spite of the rise of new communication technologies (e.g., 5G) providing an opportunity to acquire Design-Operation Continuum Engineering methods in the context of CPSs, there are still many complex issues that need to be addressed, such as the ones related with hardware-software co-design. Therefore, the process of Design-Operation Continuum Engineering for CPSs requires substantial changes with respect to the current fragmented software development process. In this paper, we build a taxonomy for Design-Operation Continuum Engineering of CPSs based on case studies from two different industrial domains involving CPSs (elevation and railway). This taxonomy is later used to elicit requirements from these two case studies in order to present a blueprint on adopting Design-Operation Continuum Engineering in any organization developing CPSs

Spectrum-based fault localization in software product lines

Context: Software Product Line (SPL) testing is challenging mainly due to the potentially huge number of products under test. Most of the research on this field focuses on making testing affordable by selecting a representative subset of products to be tested. However, once the tests are executed and some failures revealed, debugging is a cumbersome and time consuming task due to difficulty to localize and isolate the faulty features in the SPL. Objective: This paper presents a debugging approach for the localization of bugs in SPLs. Method: The proposed approach works in two steps. First, the features of the SPL are ranked according to their suspiciousness (i.e., likelihood of being faulty) using spectrum-based localization techniques. Then, a novel fault isolation approach is used to generate valid products of minimum size containing the most suspicious features, helping to isolate the cause of failures. Results: For the evaluation of our approach, we compared ten suspiciousness techniques on nine SPLs of different sizes. The results reveal that three of the techniques (Tarantula, Kulcynski2 and Ample2) stand out over the rest, showing a stable performance with different types of faults and product suite sizes. By using these metrics, faults were localized by examining between 0.1% and 14.4% of the feature sets. Conclusion: Our results show that the proposed approach is effective at locating bugs in SPLs, serving as a helpful complement for the numerous approaches for testing SPLs.Ministerio de Economía y Competitividad TIN2015-70560-R (BELI)Junta de Andalucía P12-TIC-1867 (COPAS

Performance-Driven Metamorphic Testing of Cyber-Physical Systems

Cyber-physical systems (CPSs) are a new generation of systems, which integrate software with physical processes. The increasing complexity of these systems, combined with the un certainty in their interactions with the physical world, makes the definition of effective test oracles especially challenging, facing the well-known test oracle problem. Metamorphic testing has shown great potential to alleviate the test oracle problem by exploiting the relations among the inputs and outputs of different executions of the system, so-called metamorphic relations (MRs). In this article, we propose an MR pattern called PV for the identification of performance-driven MRs, and we show its applicability in two CPSs from different domains, which are automated navigation systems and elevator control systems. For the evaluation, we as sessed the effectiveness of this approach for detecting failures in an open-source simulation-based autonomous navigation system, as well as in an industrial case study from the elevation domain. We derive concrete MRs based on the PV pattern for both case studies, and we evaluate their effectiveness with seeded faults. Results show that the approach is effective at detecting over 88% of the seeded faults, while keeping the ratio of FPs at 4% or lower.European Union's Horizon 2020 Research and Innovation Programme (Grant Number: 871319)Junta de Andalucía US-1264651 (APOLO)Junta de Andalucía P18-FR-2895 (EKIPMENT-PLUS)Ministerio de Ciencia e Innovación RTI2018-101204-B-C21 (HORATIO)Mondragon Unibertsitatea IT1519-2

Sormena, berrikuntza eta komunikazio ikasketak: "Design thinking eta creation nets" metodologien aukerak aztertzen

Internet y las innovaciones tecnológicas en curso están ejerciendo un impacto apreciable tanto en el periodismo como en la educación en comunicación. Son muchas las universidades y escuelas de periodismo que están tratando de adaptar sus planes de estudio al nuevo panorama. La innovación y la creatividad se consideran conceptos clave para hacer frente al nuevo y cambiante entorno mediático, pero, ¿qué dice el Libro Blanco de los títulos de Grado en Comunicación acerca de ambos conceptos? ¿Tienen estos conceptos cabida en las propuestas curriculares para los Grados en Comunicación en España? ¿Cómo se podría fomentar la presencia de la creatividad y la innovación en los currículos de dichos Grados? Este documento describe por una parte la iniciativa Innovation Journalism, desarrollada en el Stanford Center for lnnovation and Communication (Stanford University), y da cuenta, asimismo, de dos metodologías (Design Thinking y Creation Nets) que pueden ser utilizadas para fomentar la presencia de la creatividad y la innovación en los currículos

Sormena, berrikuntza eta komunikazio ikasketak: "Design thinking eta creation nets" metodologien aukerak aztertzen

Internet y las innovaciones tecnológicas en curso están ejerciendo un impacto apreciable tanto en el periodismo como en la educación en comunicación. Son muchas las universidades y escuelas de periodismo que están tratando de adaptar sus planes de estudio al nuevo panorama. La innovación y la creatividad se consideran conceptos clave para hacer frente al nuevo y cambiante entorno mediático, pero, ¿qué dice el Libro Blanco de los títulos de Grado en Comunicación acerca de ambos conceptos? ¿Tienen estos conceptos cabida en las propuestas curriculares para los Grados en Comunicación en España? ¿Cómo se podría fomentar la presencia de la creatividad y la innovación en los currículos de dichos Grados? Este documento describe por una parte la iniciativa Innovation Journalism, desarrollada en el Stanford Center for lnnovation and Communication (Stanford University), y da cuenta, asimismo, de dos metodologías (Design Thinking y Creation Nets) que pueden ser utilizadas para fomentar la presencia de la creatividad y la innovación en los currículos