According tO the features of engineering domains．this paper presents a semantic hypergraph model based on relation and network，in order to express many tO many relations of different semantic classes．The management mechanism expressed by the model and the basic data of databases are managed and run in main memory，thus the access efficiency of engineering data is increased．C language interface which includes general and spacial functionalities is proposed for meeting requirements of engineering applications．The EDBMS(engineering database management system)with above research results is implemented and has been actually used for engineering domains．