@Carl Love 

Yes, I thougt that too. After playing the setting, I get nowhere.

I am using Maple in Chinese Win 7. Maybe that's why. Just guess.

@ecterrab 

I simply followed the  "An Overview of General Relativity computations with DifferentialGeometry"

http://www.maplesoft.com/support/help/Maple/view.aspx?path=DifferentialGeometry/OverviewOfGeneralRelativity

and typed the commands interactively.

->with(DifferentialGeometry); with(Tensor); with(Tools);

->DGsetup([t, r, theta, phi], M1, verbose);
 
The following coordinates have been protected:
[t, r, theta, phi]

The following vector fields have been defined and protected:

Error, (in Typeset:-Tdisplay[true]) `alias` does not evaluate to a module

Since I am learning GR now, I 'd like to use maple to help me to calculate (varify my own calculation) the various tensors, like killing. Later, to solve the classical GR problems.

Thanks