MDAC 2.5 SDK - OLE DB Programmer's Reference
Chapter 22: OLE DB for OLAP Objects and Schema Rowsets
The command object supports text commands in the MDX syntax by using the OLE DB ICommandText interface. Consumers use the ICommandText::SetCommandText method to specify the command and the ICommand::Execute method to process the command. For commands that may be used several times, consumers can prepare the command with the ICommandPrepare::Prepare method. For a complete discussion of the OLE DB command object, see "Command Objects" in Chapter 1, "Overview of OLE DB." For additional information about the MDX syntax defined by OLE DB for OLAP and its use, see "Datasets and Multidimensional Expressions" in Chapter 21, "OLE DB for OLAP Concepts." Also see Chapter 24, "Multidimensional Expressions."
OLE DB for OLAP defines a GUID that denotes the MDX syntax: MDGUID_MDX. This GUID is used in ICommandText::SetCommandText to notify the provider that the query language being used is the MDX syntax defined in Chapter 25, "MDX Grammar."