How to: View the Report Definition Language Source (Reporting Services)
In Report Designer in Business Intelligence Development Studio, you can view the underlying XML structure of a report definition. A report definition is saved as a Report Definition Language (.rdl) file. When you switch from Design to Preview in Report Designer, changes you made to the report on the report design surface are translated to RDL elements and properties, validated against the report definition schema, and saved in the .rdl file.
To access Report Definition Language (RDL)
In Solution Explorer, open the report.
On the View menu, click Code.