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.

Authors: Jon Ayerdi∗, Sergio Segura†, Aitor Arrieta∗, Goiuria Sagardui∗ and Maite Arratibel

Mondragon Unibertsitatea∗, Universidad de Sevilla †, Orona ‡ 

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.

Authors: Jon Ayerdi∗ , Aitor Garciandia† , Aitor Arrieta∗ , Wasif Afzal‡ , Eduard Enoiu‡ , Aitor Agirre† , Goiuria Sagardui∗ , Maite Arratibel§ and Ola Sellin¶

University of Mondragon ∗, Ikerlan †, Malardalen University  ‡, Orona §, Bombardier Transportation ¶,

Handling Uncertainties in Cyber-Physical Systems during Their Operations with Digital Twins

It is a well-recognized fact that a Cyber-Physical System (CPS) experiences uncertain (including unknown) situations during their operations. Some of such uncertainties could potentially lead to failures of CPS operations. Factors contribute to such uncertainties include 1) the intrinsically unpredictable physical environment of a CPS, 2) the use of communication networks continuously experiencing problems (e.g., slower connection than expected), and 3) the increasing use of machine learning algorithms in CPSs which introduce inherent uncertainties to these CPSs.

No matter how meticulously a CPS is designed and developed, it is impossible to predict all possible uncertain situations it will experience during its operation. Thus, there is a need for new methods for discovering and handling uncertain situations during the CPS operation to prevent it from failure. In this paper, we present our ideas on how digital twins, i.e., “live models” of CPSs can help in discovering and handling potentially unsafe situations during its operation.

We present the research challenges and potential solutions to develop, deploy, and operate such digital twins.

Authors: Shaukat Ali & Tao Yue, from Simula Research Laboratory, Norway