## 2 Related Work  
Major software product line engineering methods include software product line engineering [2], RSEB [3] and FAST [4]. Variability is a core issue in the theoretical study of product line technology, and there are mainly FODA [5], FORM [6], and other methods. The modeling of feature variability is an important part of product family domain engineering. For example, [PERSON] [14] proposes a variability-based model that models variability in software product lines through four approaches: parameterization, information hiding, inheritance, and variation points. [PERSON] [15] unifies the modeling of variability across all abstraction layers of a software product family by treating variation points and dependencies as monadic relationships. [PERSON] [16] used variability features to describe the development process of a product line and proposed a unified meta-model that can represent the dependencies of variability features at different stages. In the literature [17], a semi-automatic domain requirement modeling method for software product lines is proposed, based on the idea of separation of concerns, using feature models to represent different aspects of the features information of the products in the software product line, and the construction of the domain requirement model is realized by the comparison and combination of feature models. In [18], the authors propose using Extensible Markup Language (XML) architecture and Extensible Stylesheet Language Transformations (XSLT) files to manage the variability of feature modeling, enabling the complete package from product line engineering to specific product implementation. Researchers have proposed a number of proven methods around feature variability modeling, supported by tools such as Feature-IDE that have provided the industry with usable systematic modeling tools [19]. The tool [20] was originally built for AHEAD as an IDE that integrated all phases of feature-oriented software development, and later researchers refactored Feature-IDE into an open-source framework [21] in order to make it available for other tools and languages. The above approach is mainly for the improvement of the product family variability modeling method and lacks a complete requirement analysis process for the product family model from the feature model to the specification of each product. Some researchers have clarified the functions of each feature in the product family model through feature specification. In the process of feature specification, a clarification of the feature model is provided. In [22], the authors analyze feature functionality from the perspective of functional interactions, a process that achieves intrinsic functional integrity of features and reduces functional coupling. The literature [23] proposes a combined business process analysis and feature analysis approach to assess the quality of software product family models. The literature [24] introduces the role of feature specification through an example of automotive software product line development. The method uses the results of feature specification description to guide structured analysis and development and reduces development costs by reconstructing the product line structure through data flow and state transition analysis. These studies mentioned above used informal language in describing the feature specifications. Inconsistencies can exist between feature specification descriptions, and these are difficult to detect. A non-formal analysis approach also makes it difficult to use tools to automate the checking of problems. Formal specifications can prevent major errors in the early stages of a software project by precisely defining operational behavior and making it easy to build the associated automated support software. There is some work that introduces formal methods into the modeling of product families in the hope of improving the quality of product line engineering models through formal methods.