document: The existence condition of gamma - acyclic database schemes with MVDs constraints It is very important to use database technology for a large-scale system such as ERP and MIS . A good database design may improve the performance of the system . Some research shows that a gamma - acyclic database scheme has many good properties , e.g. , each connected join expression is monotonous , which helps to improve query performance of the database system . Thus what conditions are needed to generate a gamma - acyclic database scheme for a given relational scheme ? In this paper , the sufficient and necessary condition of the existence of gamma - acyclic , join-lossless and dependencies-preserved database schemes meeting 4NF is given
doc_bio_tags: O B I O O O O O O O B I O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I I O O O O O O O O O O O O O O O O O
extractive_keyphrases: existence condition database technology connected join expression query performance sufficient and necessary condition mvds constraints
abstractive_keyphrases: large-scale system gamma -acyclic database schemes