Assign a name to a data table by sending it the Set Name message. The argument is a filename in quotation marks, or something that evaluates to a filename.
dt = Open( "$SAMPLE_DATA/Big Class.jmp" );
dt << Set Name( "New Big Class.jmp" );
s = "New Big Class";
dt << Set Name( s );
To retrieve the name, send a Get Name message to the data table:
dt << Get Name();
"New Big Class"