Software-intensive Systems-of-Systems Research Articles

Towards an understanding of reliability of software-intensive systems-of-systems

Large-scale software-intensive Systems-of-Systems (SoS) have become present in several critical domains and have sometimes depended on diverse trending technologies, such as cloud computing and machine learning. At the same time, the SoS dynamic architecture makes it difficult to assure SoS reliability leading to diverse studies with specific solutions, while the need for a shared view of what precisely SoS reliability refers to still exists. The main contribution of this article is to go towards an understanding of SoS reliability. We present a conceptual model whose concepts as well as their definitions and relationships were defined by systematically examining the literature of the field. We surveyed 36 practitioners and researchers regarding ambiguity, explanatory power, parsimony, generality, and utility of our model. Next, we adjusted our model according to their contribution. We reach a conceptual model containing 29 concepts and their relationships that help to comprehend SoS reliability. In addition, we provided a glossary with a definition of each concept of our conceptual model. We also proposed a SoS reliability definition grounded on the literature. By organizing the knowledge of SoS reliability, this conceptual model makes it possible to expand the body of knowledge in the area and opens several opportunities for further investigations; in particular, this model serves as a basis for novel solutions aiming to assure SoS reliability.

A Systematic Identification of Formal and Semi-Formal Languages and Techniques for Software-Intensive Systems-of-Systems Requirements Modeling

Software-intensive Systems-of-Systems (SoS) refer to an arrangement of managerially and operationally independent systems(i.e., constituent systems), which work collaboratively towards the achievement of global missions. Because some SoS are developed for critical domains, such as healthcare and transportation, there is an increasing need to attain higher quality levels, which often justifies additional costs that can be incurred by adopting formal and semi-formal approaches (i.e., languages and techniques) for modeling requirements. Various approaches have been employed, but a detailed landscape is still missing, and it is not well known whether they are appropriate for addressing the inherent characteristics of SoS. The main contribution of this article is to present this landscape by reporting on the state of the art in SoS requirements modeling. This landscape was built by means of a systematic mapping and shows formal and semi-formal approaches grouped from model-based to property-oriented ones. Most of them have been tested in safety-critical domains, where formal approaches such as finite state machines are aimed at critical system parts, while semi-formal approaches (e.g., UML and i*) address non-critical parts. Although formal and semi-formal modeling is an essential activity, the quality of SoS requirements does not rely solely on which formalism is used, but also on the availability of supporting tools/mechanisms that enable, for instance, requirements verification along the SoS lifecycle

Addressing the Integration Challenge for Avionics and Automotive Systems—From Components to Rich Services

Automotive and avionics systems are complex, distributed, software-intensive systems-of-systems (SoS). Consequently, system integration is a central challenge in both domains. Important cross-cutting requirements aspects, such as security, authorization, and failure management, are best understood as properties of the interplay among sub-systems. Yet, traditional development processes address the integration challenge only late, at the level of implementation and deployment. Consequently, potentials for reuse within and across product lines are left unrealized. Furthermore, late integration leads to high calibration, configuration and redesign costs. Service-Oriented Architectures (SOAs) have emerged as a solution to the integration challenge. However, inappropriate application of SOA-principles results in a high degree of fragmentation and scattering of functionality-this leads to additional difficulties in requirements traceability and quality assurance. In this article, we give a comprehensive overview of these SOA-challenges, and present Rich Services as a hierarchical SOA blueprint and development process enabling SoS integration in a dependable way. Rich Services introduce services as hierarchical, partial interaction patterns; these interactions are then augmented with infrastructure elements to inject behaviors that address cross-cutting requirements aspects. Rich Services also seamlessly address the mapping from logical to deployment architectures. Using end-to-end failure management as an example, we illustrate the utility of Rich Services.

Cost modeling of distributed team processes for global development and Software‐Intensive Systems of Systems

AbstractDistributed team processes are becoming more pervasive because of geographically distributed development and complex Software‐Intensive Systems of Systems (SISOS) with many layers of breadth and depth. Software is developed collaboratively in multiple locations around the world, and projects are being contracted out in whole or in part for economic leverage. Systems are becoming larger and more complex, leading to distributed processes at many levels. Projects are often split among distributed teams, where the teams contribute different portions of work per phase to take advantage of their skill sets and rates. Thus there is a need for new parametric cost estimation models where effort multipliers are phase sensitive. Working with industrial partners, a set of constructive cost models have been extended to better estimate distributed teams where work is allocated by phase, rather than just along the lines of specific functionality. The distributed development models allow for work distribution by phase per team (and per module), different environmental characteristics of the teams, localized labor categories, calendars, compensation rates, and currencies for costing. They also use a generalized scheme for user‐defined global life‐cycle processes that include calibrated effort and schedule distributions. Representative examples show the models being used for global development and SISOS scenarios. Copyright © 2008 John Wiley & Sons, Ltd.

Assessing hybrid incremental processes for SISOS development

AbstractNew processes are being assessed to address modern challenges for Software‐Intensive Systems of Systems (SISOS), such as coping with rapid change while simultaneously assuring high dependability. A hybrid agile and plan‐driven process based on the spiral lifecycle has been outlined to address these conflicting challenges with the need to rapidly field incremental capabilities in a value‐based framework. A system dynamics model has been developed to assess the incremental hybrid process and support project decision making. It estimates cost and schedule for multiple increments of a hybrid process that uses three specialized teams, and also considers the mission value of software capabilities. It considers changes due to external volatility and feedback from user‐driven change requests, and dynamically reestimates and allocates resources in response to the volatility. Deferral policies and team sizes can be experimented with, and it includes trade off functions between cost and the timing of changes within and across increments, length of deferral delays, and others. We illustrate how the model can be used to determine optimal agile team size to handle changes. Both the hybrid process and simulation model are being evolved on a very large scale incremental SISOS project and other potential pilots. Copyright © 2007 John Wiley & Sons, Ltd.