This paper presents a comprehensive review of geometric constraint solving in parametric computer-aided design (CAD), with the major focus on its advances in the last 15 years. Geometric constraint solving can date back to the very first CAD prototype, Sketchpad, in the 1960s, but serious research studies were carried out only after parametric CAD was introduced in the late 1980s. In the following 30-year history of GCS research, two development stages may be identified: (1) the first 15 years (late 1980s -mid 2000s) were primarily devoted to geometric constraint decomposition for well-constrained systems or those with only structural constraint dependencies; and (2) the second 15 years (late 2000s -now) have seen research efforts shifted towards classification criteria and decomposition algorithms for general constraint systems (with and without non-structural constraint dependencies). Most existing reviews focused on the first 15 years. The problem researched in the second 15 years is, however, equally important, considering that a manually specified constraint system usually contains under-and over-constrained parts, and that such parts must be correctly detected and resolved before numerical solving can work. In this regard, this review paper covers both stages and will discusses what has already been made possible for handling general constraint systems, what developments can be expected in the near future, and which areas remain problematic.

System-of-systems (SoS) architecture is crucial in managing complex and interconnected systems. However, the description and modeling of SoS architecture pose significant challenges and require a structured and organized approach. In this study, a metamodel for SoS architecture that considers both structural and behavioral perspectives is defined. The metamodel is then mapped to ontologies that are enhanced with a flow-based extension to characterize architecture views. On this basis, an SoS capability ontology (SoSCO) and an SoS operational ontology (SoSOO) are built with factors, relationships, and flows. A four-step architecture process for developing capabilities and a five-step architecture process for operational modeling are provided based on the ontologies. The proposed approach is applied in a search and rescue case study, demonstrating its ability to improve operability in the early design stage. The process is implemented using the Unified Architecture Framework (UAF) so that various stakeholders and engineers can better understand and develop an SoS.

Model-Based Systems Engineering (MBSE) and the Systems Modeling Language (SysML) have become one of the best way to develop the design of complex equipment systems. The current modeling tools are all stand-alone. However, the system design of complex equipment is a complex task that requires the collaboration of experts from different disciplines and fields. The Web-based collaborative modeling method has always been a prioritized option because it has many advantages, such as “light” client, convenient maintenance, high model reliability, etc. However, how to implement the Web-based collaborative SysML modeling has always been a challenge. In this study, a Web-based collaborative SysML modeling method proposed for model-based systems engineering. First, the architecture of the Web-based collaborative SysML modeling platform is designed, and solutions for two collaborative scenarios of asynchronous collaboration and synchronous collaboration are also given. Secondly, through the application scenario analysis of asynchronous collaboration, the mechanism of authority management and access control which is suitable for the SysML model is proposed to realize security control of the model data. Then, the key technology of the SysML real-time collaborative modeling system is studied, and the problems of graphical collaborative editing concerned graphics concurrency control and consistency maintenance are solved. Finally, a prototype system for Web-based SysML collaborative modeling is implemented and a case study is given to demonstrate the effectiveness of the proposed method.

No abstract

A system of systems (SoS) composes a set of independent constituent systems (CSs), where the degree of authority to control the independence of CSs varies, depending on different SoS types. Key researchers describe four SoS types with descending levels of central authority: directed, acknowledged, collaborative and virtual. Although the definitions have been recognized in SoS engineering, what is challenging is the difficulty of translating these definitions into models and simulation environments. Thus, we provide a goal-based method including a mathematical baseline to translate these definitions into more effective agent-based modeling and simulations. First, we construct the theoretical models of CS and SoS. Based on the theoretical models, we analyze the degree of authority influenced by SoS characteristics. Next, we propose a definition of SoS types by quantitatively explaining the degree of authority. Finally, we recognize the differences between acknowledged SoS and collaborative SoS using a migrating waterfowl flock by an agentbased model (ABM) simulation. This paper contributes to the SoS body of knowledge by increasing our understanding of the degree of authority in an SoS, so we may identify suitable SoS types to achieve SoS goals by modeling and simulation.