信息物理融合系统的软件需求分析

摘要

计算过程与物理过程的融合使得信息物理融合系统（Cyber-Physical Systems，CPS）的软件需求分析成为一个具有挑战性的任务。首先，分析人员需要从用户所期望实现的物理实体变化出发，基于对物理实体性质的认识来推理分析软件需求；其次分析人员已不能将 CPS 中的软件看成一个整体去描述它的外部行为，而需要分析 CPS所应包含的各个软件实体和物理实体，描述每个物理实体的性质和软件实体应具有的行为；还有计算过程与物理过程的融合也使得分析人员必须采取一种统一的方式来描述物理实体的性质和软件实体的行为，以方便用户需求的满足性验证。基于问题框架方法和面向目标方法，作者提出了一种适合于 CPS 的软件需求分析方法。该方法采用现象间的因果关系式这一具体形式来统一描述 CPS 中物理实体的性质和软件实体的需求，然后从用户所期望的物理现象出发，遵循面向目标的方法，将 CPS 软件需求的分析过程转化为建立满足用户需求的现象间因果关系链的过程，最后通过基于 Alloy 的目标现象可达性验证来检验用户需求的可满足性；并且用一个自适应巡航控制系统的案例来说明所提方法的可行性。%The integration of computing process with physical process makes the software requirements analysis for Cyber-Physical Systems (CPS)a challenging task.First,software requirements need to be derived from the desired changes of physical entities and the properties of such physical entities.Second,analysts can’t treat the software as a whole and describe its external behaviors. Instead,they need to analyze the software entities and physical entities composing CPS and capture the properties of each physical entity and desired behaviors of each software entity.Finally,a unified way is required to describe the properties of physical entities and the behaviors of software entities to help validate the satisfaction of user’requirements.Based on problem frame and goal oriented approaches,this paper proposes an approach to address this task.It describes the properties of physical entities and the behaviors on software entities in CPS as the causal relations between phenomena.Starting from the physical phenomena desired by users,it then follows the goal based analysis process,transforms the software requirements analysis into building the phenomena causal chains required to meet users’requirements,and finally validates the satisfactions of users’requirements by checking whether the desired phenomena in the causal chains can be reached through describing the causal chains with Alloy.An adaptive cruise control system has been taken as an example to show the feasibility.