OGSA-DAI通过数据服务对后端单个数据源查询，将整串SQL语句推送给后端数据库执行查询。而在面向分布式数据源的DQP查询中，组合查询在中间层被解析为针对不同数据源的子查询，子查询通过DAI数据服务获取查询结果，并在DQP中间层对不同数据源返回的结果进行组装，并返回给请求用户。-OGSA-DAI data services through a single back-end data source query, push the whole string of SQL statements sent to the back-end database, execute the query. In the distributed data sources for the DQP query, combined query is resolved in the middle layer for different data sources for the sub-query, sub query DAI data services through access to query results, and the middle layer in the DQP return different data sources The results were assembled, and returned to the requesting user.