Mapping Publishing and Mapping Adaptation in the Middleware of Railway Information Grid System

When adopting the mediator architecture to integrate distributed, autonomous, relational model based database sources, mappings from the source schema to the global schema may become inconsistent when the relational source schema or the global schema evolves. Without mapping adaptation, users may access no data or wrong data. In the paper, we propose a novel approach the global attribute as view with constraints (GAAVC) to publish mappings, which is adaptive for the schema evolution. Also published mappings satisfy both source schema constraints and global schema constraints, which enable users to get valid data. We also put forward the GAAVC based mapping publishing algorithm and mapping adaptation algorithms. When we compare our approach with others in functionality, it outperforms. Finally the mapping adaptation tool GMPMA is introduced, which has been implemented in the middleware of railway information grid system.