The document discusses using a mediator-based architecture and web services to provide uniform access to distributed heterogeneous air quality data sources. Key points include: - A mediator server can homogenize data coding/formatting from various sources, allowing users to access data through a simple universal interface while minimizing changes to data providers. - Services like Dvoy use mediators and wrappers to resolve technical and logical heterogeneity across sources and provide multidimensional querying of spatial-temporal data cubes. - This approach facilitates data sharing and integration for improved analysis to address challenges from secondary pollutants and more participatory management of air quality.