A cloud-oriented two-layer database model and itsalgebraic operations

Abstract

The existed cloud data models cannot well meet the management requirements of structured data including a great deal of relational data, therefore a two-layer cloud data model is proposed by referencing the relation data model, Hierarchical data model and key value data model. In the representation layer, the concepts of composite class and composite object are proposed to represent nested data structure and its instance. In the storage layer, two different triples are proposed to represent non-nested data structure and its instance. The conception of Rule is proposed to represent the relations of the data, and the conception of CAO (Component-Attribute-Object) is proposed to represent the data in non-nested data instance. The proposed model is fit for the management requirements of structured data in the cloud for using nested data to avoid join operation and using key-value model to store data. Algebraic operations including set operations and query operations are defined by referencing the algebraic operations of relation data model based on the proposed model. The conception of simple nested object is proposed to be the operation operand for set operation and selecting operation; therefore these operations have simple expression and ensure a correct result. The conception of attribute tree is proposed and is applied in the query operation to offer attributes selection. Theoretical analysis and example validation show that the proposed database model is effective and its algebraic operations are correct.