A report definition file specifies the RDL namespace for the version of the report definition schema that is used to validate the rdl file. When you open an .rdl file in a report authoring environment such as Report Designer in SQL Server Data Tools (SSDT), Visual Studio, or Report Builder. If the report was created for a previous namespace, a backup file is automatically created, and the report is upgraded to the current namespace. If you save the upgraded report definition, you have saved the converted .rdl file. This is the only way to upgrade a report definition. The report definition itself is not upgraded on a report server. The compiled report is upgraded on a report server. For more information, see Upgrade Reports.
How to: Identify the RDL schema version on the Report Server
<xsd:schema xmlns:xsd=”http://www.w3.org/2001/XMLSchema” xmlns=”http://schemas.microsoft.com/sqlserver/reporting/*year*/01/reportdefinition” targetNamespace=”http://schemas.microsoft.com/sqlserver/reporting/*year*/01/reportdefinition” elementFormDefault=”qualified”>
The report definition namespace is specified by the following URL: