# Integration of EMU Overall Design Model Based on Ontology-Knowledge Collaboration
## 3 Integration of EMU Requirement Models
### Construction of Requirement KG  
After completing the construction of the requirement ontology, it is further instantiated and expanded through the KG. Serving as the formal specification of knowledge, the ontology defines the overall concepts, relationships, and attributes of the requirements, forming the structural and semantic foundation of the graph. Combined with graph technology, specific information about the requirements is integrated and shared with other relevant domain knowledge, achieving the instantiation representation of requirements. By incorporating the requirement ontology into this framework, richer and more accurate information can be provided to the KG, making the expression of the entire KG more comprehensive and precise. Therefore, the combination of the requirement ontology and the KG can fully leverage the role of the ontology in KG construction, enhancing the expressive power and application value of the KG, thus providing greater impetus for domain research and practical applications. The KGs are represented in the form of triplets, i.e., (Entity1, Relationship, Entity2) or (Entity, Relationship, Attribute), where entities and attributes are nodes and relationships  
Figure 8: Conversion between ReqIF model and ontology. Figure 7: Requirements ontology visualization. are directed edges connecting the two nodes. Triplets link entities or attributes and their relationships to form a KG with a network structure [41]. Commonly used large-scale KGs include Freebase, Google KG, DBpedia, and YAGO [42]; commonly used graph databases include Neo4j [43], Amazon Neptune, and Onto text Graph DB. In recent years, KG technology, with its ability to integrate data and efficiently query, visualize, intelligently infer, and easily maintain and update, has been applied in various fields such as smart education [44], aviation KG [45], smart healthcare [46], and smart e-commerce [47],achieving significant results. In smart education, the previous knowledge model about extracting knowledge from digital textbooks has been expanded [44]. Knowledge management of natural language text through knowledge graphs in the Aviation Assembly Domain [45]. The methods for constructing knowledge bases typically include automated construction, semi-automated construction, and manual construction. In the field of EMU, due to the high requirements for KGs, simple automated construction methods result in poor subsequent application effects in regard to the KG. To ensure the high-quality construction of the knowledge base, the seven-step method proposed by Stanford University for domain ontology construction [48] was adopted on the basis of manual construction of the knowledge base to construct the KG model of EMU requirements. The data of EMU overall design are mostly semi-structured and unstructured, and the knowledge corpus is complex. To meet the requirements of high accuracy and visualization of the KG, the EMU overall design adopts a combination of \"top-down\" based on ontology and \"bottom-up\" based on KGs for construction. The construction process of the EMU requirement KG involves obtaining requirement entities and extracting requirement relationships. Through this step, we obtained a series of triplets of entities and entity relationships. These triplets are stored in the Neo4j database in an ordered manner according to the type of relationship, forming a knowledge base related to requirement engineering. The Neo4j database, as the storage engine of the knowledge base, has the advantages of a graph database. This storage method helps to effectively handle complex relationships between entities and supports flexible query operations, making the knowledge base efficient and available. Through the front-end display function of Neo4j, the EMU architecture KG can be intuitively displayed. This provides the project with an intuitive visual display, allowing users to delve into the knowledge structure and relationships of the EMU overall design domain.