Milena Guessi

The state of the art and future perspectives in systems of systems software architectures

Currently, software systems have become increasingly large and complex, often resulted by the integration of several operationally independent systems, resulting in a new class of systems: the Systems of Systems (SoS). In another perspective, software architectures play a major role in determining system quality, since they form the backbone of any successful software-intensive system. Attention given to the software architectures of SoS is also certainly fundamental to the success of such systems. However, it is observed that there is a lack of works that present a wide and, at the same time, a detailed panorama about how SoS architectures have been treated. In this scenario, the main contribution of this paper is to present the state of the art on software architectures of SoS, mainly regarding their development, representation, evaluation, and evolution. This work also contributes with future research topics on SoS architectures that should be still investigated. Besides that, we intend this paper opens new perspectives of research in the software architecture area, intending to contribute to the success of SoS.

A systematic literature review on the description of software architectures for systems of systems

Software architectures have been recognized as the backbone to the success of any software system. In addition, they are responsible to aggregate quality attributes, such as interoperability, dependability, and maintainability, to these systems. In parallel, currently, a new class of complex software systems has emerged, referred as Systems of Systems (SoS), resulting from a number of operationally and managerially independent software systems working together to fulfill a mission that none system alone could provide. Considering their complexity, the development of SoS has demanded special attention to their software architectures. In this scenario, the description of such architectures, i.e., the way that these architectures are represented/documented, becomes quite important as it can improve communication as well as evaluation and maintenance of these architectures. Despite its relevance, there is still no complete panorama about architectural descriptions of SoS. The main contribution of this paper is to present results of a Systematic Literature Review (SLR) on how SoS software architectures have been described. As main result, there are already important contributions in that direction; however, there is a lack of consensus on how better dealing with these descriptions. We conclude this paper with directions on how a consensus could be achieved and which aspects of the SoS architectural descriptions require further investigation.

Consolidating a Process for the Design, Representation, and Evaluation of Reference Architectures

Reference architectures have emerged as a special type of software architecture that achieves well-recognized understanding of specific domains, promoting reuse of design expertise and facilitating the development, standardization, and evolution of software systems. Because of their advantages, several reference architectures have been proposed and have been also successfully used, including in the industry. However, the most of these architectures are still built using an ad-hoc approach, lacking of a systematization to their construction. If existing, these approaches could motivate and promote the building of new architectures and also support evolution of existing ones. In this scenario, the main contribution of this paper is to present the evolution of ProSA-RA, a process that systematizes the design, representation, and evaluation of reference architectures. ProSA-RA has been already applied in the establishment of reference architectures for different domains and this experience was used to evolve our process. In this paper, we illustrate an application of ProSA-RA in the robotics domain. Results achieved through the use of ProSA-RA have showed us that it is a viable, efficient process and, as a consequence, it could contribute to the reuse of knowledge in several applications domains, by promoting the establishment of new reference architectures.

Checking the architectural feasibility of Systems-of-Systems using formal descriptions

Systems-of-Systems (SoSs) are evolutionary developed from independent systems to achieve missions through emergent behavior. As concrete systems which will actually participate in an SoS are, in general, not known at design-time, SoSs need to dynamically create coalitions among possible constituent systems at run-time. Due to these uncertainties, the SoS architecture needs to be described abstractly at design-time and then concretely constituted at run-time. An abstract SoS architecture description can thereby specify the correctness properties of coalitions that can be formed among constituent systems at run-time. In particular, it is important to ensure that concrete SoS architectures that may emerge at run-time from such coalitions correctly comply with the abstract SoS architecture description. To automatically check the feasibility of such concrete SoS architectures, in its initial form as well as further evolution, this paper presents an approach that formally expresses the abstract SoS architecture description and the rules governing the organization of SoSs in concrete architectures at run-time. Then, we demonstrate how this approach is used for determining the feasibility of different coalitions in a flood monitoring SoS.

Architectural description of embedded systems: a systematic review

Embedded systems have gained more and more attention, as variety and complexity of these systems have increased. In particular, many of these systems are also critical regarding dependability, safety, security, among others. In parallel, since software architectures and reference architectures form the backbone of any successful system, including embedded systems, an important and even essential activity is to properly describe such architectures. However, to our best knowledge, there is no detailed panorama on how software architectures and reference architectures for embedded systems could be represented. Thus, the main contribution of this paper is to present and discuss results of a systematic review, aiming at providing this wide and, at the same time, deep panorama. We found out that different approaches have been proposed and used, lacking of consensus on how to better represent architectures of embedded systems. We also identified a range of quality requirements and constraints that have been considered in the architectural description of these systems. Furthermore, these results can be considered as valuable means to identify research lines that need to be further investigated.

Investigating the Model-Driven Development for Systems-of-Systems

Software-intensive systems have become increasingly large and complex and new techniques and methodologies are necessary to deal with such complexity. Model-Driven Development (MDD) has been used to deal with complex scenarios, since software models, despite details, facilitate the visualization of the whole. Moreover, MDD has been widely recognized as a way to assure quality, reducing time and effort, and making possible the automatic transformation of models to generate source code. In this direction, software-intensive Systems-of-Systems (SoS) is a class of software systems that have emerged over the iminence of large systems which have a high-level of complexity. Considering the success of MDD in other areas, we decided to investigate how MDD has been used in the context of SoS. This paper presents results of a Systematic Literature Review conducted to scrutinize and bring to light the state of the art in the field of MDD for SoS. Besides that, we discuss future research directions and perspectives, aiming at contributing to the development of SoS.

ASAS: An Approach to Support Simulation of Smart Systems

Smart systems, such as smart cities, smart buildings, and autonomous cars, have recently gained increasing popularity. Each such system is essentially a System-of-Systems (SoS). SoS are dynamically established as alliances among independent and heterogeneous software systems to offer complex functionalities as a result of constituents interoperability. An SoS often supports critical application domains, and, as such, must be reliable. Many SoS have been specified and evaluated for their correct operation using static models. However, specification languages have not supported to capture their inherent dynamic nature nor enabled to monitor their operation. The main contribution of this paper is to present ASAS, an approach to Automatically generate Simulation models for smArt Systems (ASAS) in order to support evaluation of their operation. In particular, our approach makes it possible to transform formal models of the SoS architecture (expressed in SoSADL) into simulation models (expressed in DEVS). We evaluated our approach by conducting two case studies using a flood monitoring system that is intended to be part of a smart city. Results indicate that ASAS can successfully generate functional simulations for the SoS operation, which in turn can enable to reason and monitor an SoS operation, taking into account its dynamic nature. Keywords-System-of-Systems; Simulation; Model-Based Engineering.

OntolAD: a formal ontology for architectural descriptions

Architecture descriptions have been the focus of several studies in which they contribute for the design, evaluation, and evolution of software systems. In parallel, ontologies have been proposed for sharing and disseminating knowledge on a particular domain. In this scenario, the ontology proposed in the ISO/IEC/IEEE 42010 standard for architecture descriptions represents an important effort towards improving architecture descriptions as it establishes a common vocabulary. Nonetheless, a formal ontology for this standard could also support automatic conformance validation and enhance architectural descriptions reuse. However, a formal ontology for this standard is not available yet. Therefore, the main contribution of this paper is the proposal of OntolAD, a formal ontology expressed in OWL 2 for the ISO/IEC/IEEE 42010 standard. We demonstrate the feasibility of our formal ontology by applying it for describing the service-oriented architecture style (SOA). We conclude this study with interesting perspectives of using this ontology in future work.

Variability viewpoint to describe reference architectures

Reference architectures have emerged as a special type of software architecture that achieves well-recognized understanding of specific domains. Their purpose is therefore to be a guidance for the development, standardization, and evolution of systems of such domains or neighbor domains. Adequate representation of such architectures is essential to promote their effective use and dissemination, using, for instance, different architectural viewpoints. A comprehensive description of reference architectures should not only record common features and functionalities, but also variations that could be present in the instances of these architectures. In this scenario, the main contribution of our work is to propose an architecture viewpoint to represent variability in reference architectures. We also describe the steps for creating such viewpoint and present an example of a technique that could be used to represent it. A case study is also presented, demonstrating the feasibility of our approach. Based on initial results, we have observed that the variability viewpoint could contribute to a more adequate, complete description of reference architectures and, as a consequence, it could promote a more effective dissemination and use of such architectures.

Software architecture and reference architecture of software-intensive systems and systems-of-systems: contributions to the state of the art

Complex software-intensive systems are more and more required as a solution for diverse critical application domains; at the same time, software architecture and also reference architecture have attracted attention as means to more adequately produce and evolve such systems. The main goal of this paper is to summarize our principal contributions in software architecture and reference architecture of software-intensive systems, including Systems-of-Systems. We intend this work can also inspire the opening of other related research lines towards founding the sustainability of such software-intensive systems.