spaceAPPS – A modular approach for on-board software

Software modularity and partial qualification capabilities are key enablers to produce cost efficient software in highly regulated domains. The modular concept (called spaceAPPS) described in this paper has been developed in the frame of the OPS-SAT project aiming at missions where flexibility is one of the success factors. spaceAPPS implements a novel software architecture for satellites inspired by the Apps concept of modern smartphones. In the European space domain the operation of a satellite is based on a set of 18 services. Accordingly, in spaceApps these services are mapped to individual Apps. This is not a one-to-one mapping which means that one App implements one or more services. During OPS-SAT ground testing it was demonstrated that functionality could be easily added through a new App or updated through replacing an existing App. Also during OPS-SAT ground testing it could be shown that a failing UserApp did not impact the basic apps to operate the satellite. Thus, it is possible to run applications of different criticality on the same platform. With operating systems supporting time and space separation the risk of failure propagation can be further reduced. The implementation of a partial validation approach, i. e. testing of third-party Apps in a representative environment and not running the validation on the target platform is feasible but was not demonstrated.

A Survey on Different Real Time Operating Systems

To minimise development costs and enhance dependability, modern embedded system development is increasingly emphasising on software modularity and reuse. Microcontrollers are extensively employed in embedded applications that have a very specific and specialised job to complete. The embedded applications are always resource constraint which requires efficient utilization of available resources. A Real Time Operating System (RTOS) is frequently used in this context to plan task execution as well as enable intertask communication and synchronisation. This paper provides the survey of different RTOS available in market and their applications. Several open source RTOS such as Free RTOS, VxWorks, SmallRTOS and TinyOS are compared with respect to the scheduling algorithms used.

Linear Software Models: An Occam’s Razor Set of Algebraic Connectors Integrates Modules into a Whole Software System

Well-designed software systems, with providers only modules, have been rigorously obtained by algebraic procedures from the software Laplacian Matrices or their respective Modularity Matrices. However, a complete view of the whole software system should display, besides provider relationships, also consumer relationships. Consumers may have two different roles in a system: either internal or external to modules. Composite modules, including both providers and internal consumers, are obtained from the joint providers and consumers Laplacian matrix, by the same spectral method which obtained providers only modules. The composite modules are integrated into a whole Software System by algebraic connectors. These algebraic connectors are a minimal Occam’s razor set of consumers external to composite modules, revealed through iterative splitting of the Laplacian matrix by Fiedler eigenvectors. The composite modules, of the respective standard Modularity Matrix for the whole software system, also obey linear independence of their constituent vectors, and display block-diagonality. The spectral method leading to composite modules and their algebraic connectors is illustrated by case studies. The essential novelty of this work resides in the minimal Occam’s razor set of algebraic connectors — another facet of Brooks’ Propriety principle leading to Conceptual Integrity of the whole Software System — within Linear Software Models, the unified algebraic theory of software modularity.

Correction: Xiang, Y.M.; Pan, W.F.; Jiang, H.B.; Zhu, Y.F.; Li, H. Measuring Software Modularity Based on Software Networks. Entropy 2019, 21, 344

The authors wish to make the following corrections to the paper [...]

IoT Sensing Platform as a Driver for Digital Farming in Rural Africa

Small-scale farming can benefit from the usage of information and communication technology (ICT) to improve crop and soil management and increase yield. However, in order to introduce digital farming in rural areas, related ICT solutions must be viable, seamless and easy to use, since most farmers are not acquainted with technology. With that in mind, this paper proposes an Internet of Things (IoT) sensing platform that provides information on the state of the soil and surrounding environment in terms of pH, moisture, texture, colour, air temperature, and light. This platform is coupled with computer vision to further analyze and understand soil characteristics. Moreover, the platform hardware is housed in a specifically designed robust casing to allow easy assembly, transport, and protection from the deployment environment. To achieve requirements of usability and reproducibility, the architecture of the IoT sensing platform is based on low-cost, off-the-shelf hardware and software modularity, following a do-it-yourself approach and supporting further extension. In-lab validations of the platform were carried out to finetune its components, showing the platform’s potential for application in rural areas by introducing digital farming to small-scale farmers, and help them delivering better produce and increasing income.

Measuring Software Modularity Based on Software Networks

Modularity has been regarded as one of the most important properties of a successful software design. It has significant impact on many external quality attributes such as reusability, maintainability, and understandability. Thus, proposing metrics to measure the software modularity can be very useful. Although several metrics have been proposed to characterize some modularity-related attributes, they fail to characterize software modularity as a whole. A complex network uses network models to abstract the internal structure of complex systems, providing a general way to analyze complex systems as a whole. In this paper, we introduce the complex network theory into software engineering and employ modularity, a metric widely used in the field of community detection in complex network research, to measure software modularity as a whole. First, a specific piece of software is represented by a software network, feature coupling network (FCN), where methods and attributes are nodes, couplings between methods and attributes are edges, and the weight on the edges denotes the coupling strength. Then, modularity is applied to the FCN to measure software modularity. We apply the Weyuker’s criteria which is widely used in the field of software metrics, to validate the modularity as a software metric theoretically, and also perform an empirical evaluation using open-source Java software systems to show its effectiveness as a software metric to measure software modularity.

Optimizing Software Modularity with Minimum Possible Variations

Poor design choices at the early stages of software development and unprincipled maintenance practices usually deteriorate software modularity and subsequently increase system complexity. In object-oriented software, improper distribution of classes among packages is a key factor, responsible for modularity degradation. Many optimization techniques to improve the software modularity have been proposed in the literature. The focus of these optimization techniques is to produce modularization solutions by optimizing different design quality criteria. Such modularization solutions are good from the different aspect of quality; however, they require huge modifications in the existing modular structure to realize the suggested solution. Thus these techniques are costly and time consuming if applied at early stages of software maintenance. This paper proposes a search-based optimization technique to improve the modularity of the software system with minimum possible variation between the existing and produced modularization solution. To this contribution, a penalized fitness function, namely, penalized modularization quality, is designed in terms of modularization quality and the Move or Join Effectiveness Measure metric. Furthermore, this fitness function is used in both single-objective genetic algorithm (SGA) and multi-objective genetic algorithm (MGA) to generate the modularization. The effectiveness of the proposed remodularization approach is evaluated over five open-source and three random generated software systems. The experimentation results show that the proposed approach is able to generate modularization solutions with improved quality along with lesser perturbation compared to their non-penalty counterpart and at the same time it performs better with the MGA compared to the SGA. The proposed approach can be very useful, especially when total remodularization is not feasible/desirable due to lack of time or high cost.