The terms module and modularity are not part of the technical taxonomy in any of the systems engineering standards, which do not regard a module as a part of the formal system breakdown structure. In this paper, we redefine the term module as a unit composed of a set of components with a set of specific interfaces. This unit serves one or more purely nonfunctional goals, such as flexibility, evolvability, manufacturability, testability, and maintainability. According to this definition, a configuration item, a subsystem, an assembly, a subassembly, or a component can all be regarded as modules as they can serve nonfunctional goals. The important assertion here is that a module's boundaries do not necessarily coincide with those dictated by the functional or spatial system decomposition and hierarchy. The aim of this paper is to lay the foundations for the future standardization of various engineering design processes based on modularity for nonfunctional benefits. A clear definition of the terms module and modularity can assist systems designers and developers to optimize the value of a modular system. This research highlights the present inconsistencies in the field of modular system design and puts forward some critical questions, which will shape the future research into this field.

中文翻译：

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系统工程术语模块和模块化的标准描述

术语模块和模块化不是任何系统工程标准中技术分类的一部分，这些标准不将模块视为正式系统分解结构的一部分。在本文中，我们将术语模块重新定义为由一组具有一组特定接口的组件组成的单元。该单元服务于一个或多个纯非功能性目标，例如灵活性、可进化性、可制造性、可测试性和可维护性。根据这个定义，一个配置项、一个子系统、一个组件、一个子组件或一个组件都可以被视为模块，因为它们可以服务于非功能性目标。这里的重要断言是，模块的边界不一定与功能或空间系统分解和层次结构所规定的边界一致。本文的目的是为未来基于模块化的各种工程设计过程的标准化奠定基础，以实现非功能性优势。术语模块和模块化的明确定义可以帮助系统设计人员和开发人员优化模块化系统的价值。本研究突出了模块化系统设计领域目前的不一致，并提出了一些关键问题，这将塑造该领域的未来研究。