The Existence Condition of r-Acyclic Database Schemes with MVDs Constraints

It is very important to use databasetechnology for a large-scale system such as ERP and MIS. A good databasedesign may improve the performance of the system. Some researches showthat a g-acyclic database scheme has many good properties, e.g., eachconnected join expression is monotonous, which helps to improve queryperformance of the database system. Thus what conditions are needed togenerate a g-acyclic database scheme for a given relational scheme?In this paper, the sufficient and necessary condition of the existenceof g-acyclic, join-lossless and dependencies-preserved databaseschemes meeting 4NF is given.