A Cyber–Physical System (CPS) comprises physical as well as software subsystems. Simulation-based approaches are typically used to support design and Verification and Validation (V&V) of CPSs in several domains such as: aerospace, defence, automotive, smart grid and healthcare.

Accordingly, many simulation-based tools are available to support CPS design. This, on one side, enables designers to choose the toolchain that best suits their needs, on the other side poses huge interoperability challenges when one needs to simulate CPSs whose subsystems have been designed and modelled using different toolchains. To overcome such an interoperability problem, in 2010 the Functional Mock-up Interface (FMI) has been proposed as an open standard to support both Model Exchange (ME) and Co-Simulation (CS) of simulation models created with different toolchains. FMI has been adopted by several modelling and simulation environments. Models adhering to such a standard are called Functional Mock-up Units (FMUs). Indeed FMUs play an essential role in defining complex CPSs through, e.g., the System Structure and Parametrisation (SSP) standard.

Simulation-based V&V of CPSs typically requires exploring different simulation scenarios (i.e., exogenous input sequences to the CPS under design). Many such scenarios have a shared prefix. Accordingly, to avoid simulating many times such shared prefixes, the simulator state at the end of a shared prefix is saved and then restored and used as a start state for the simulation of the next scenario. In this context, an important FMI feature is the capability to save and restore the internal FMU state on demand. This is crucial to increase efficiency of simulation-based V&V. Unfortunately, the implementation of this feature is not mandatory and it is available only within some commercial software. As a result, the interoperability enabled by the FMI standard cannot be fully exploited for V&V when using open-source simulation environments. This motivates developing such a feature for open-source CPS simulation environments.

Accordingly, in this paper, we focus on JModelica, an open-source modelling and simulation environment for CPSs based on an open standard modelling language, namely Modelica. We describe how we have endowed JModelica with our open-source implementation of the FMI 2.0 functions needed to save and restore internal states of FMUs for ME. Furthermore, we present experimental results evaluating, through $934$ benchmark models, correctness and efficiency of our extended JModelica. Our experimental results show that simulation-based V&V is, on average, $22$ times faster with our get/set functionality than without it.

网络物理系统（CPS）包括物理子系统和软件子系统。基于仿真的方法通常用于支持航空航天，国防，汽车，智能电网和医疗保健等多个领域的CPS的设计以及验证和确认（V＆V）。

因此，许多基于仿真的工具可用于支持CPS设计。一方面，这使设计人员可以选择最适合其需求的工具链；另一方面，当需要模拟其子系统已使用不同工具链设计和建模的CPS时，则提出了巨大的互操作性挑战。为了克服这种互操作性问题，2010年，功能性模型接口（FMI）被提议为开放标准，以支持使用不同工具链创建的仿真模型的模型交换（ME）和协同仿真（CS）。FMI已被多个建模和仿真环境采用。遵循这种标准的模型称为功能模型单元（FMU）。实际上，FMU在通过以下方式定义复杂的CPS中起着至关重要的作用：，系统结构和参数化（SSP）标准。

CPS的基于仿真的V＆V通常需要探索不同的仿真方案（即，正在设计的CPS的外部输入序列）。许多此类方案都有一个共享的前缀。因此，为了避免多次仿真这样的共享前缀，共享前缀末尾的模拟器状态将被保存，然后还原并用作下一个场景的模拟的开始状态。在这种情况下，重要的FMI功能是按需保存和恢复内部FMU状态的功能。这对于提高基于仿真的V＆V的效率至关重要。不幸的是，此功能的实现不是强制性的，仅在某些商业软件中可用。结果，当使用开源仿真环境时，FMI不能完全利用FMI标准支持的互操作性。这激发了为开源CPS仿真环境开发此类功能的动机。

因此，在本文中，我们重点介绍JModelica，它是一种基于开放标准建模语言Modelica的CPS开源建模和仿真环境。我们将描述我们如何为JModelica赋予FMI 2.0功能的开源实现，该功能为保存和还原FMU的内部状态提供了必要。此外，我们通过$934$扩展JModelica的基准模型，正确性和效率。我们的实验结果表明，基于仿真的V＆V平均而言$22$ 使用获取/设置功能要比不使用它快一倍。