How to define different unstructured grids that share the same points (also for different time steps)

Is it possible to define different unstructured grids that share the same Points, without having to write the points in each file? This is supposing only one time-step.

I imagine that vtkMultiPieceDataSet should do so, but I don’t know how to write that in an XML file. A vtkMultiBlockDataSet groups together the unstructured grids, but the Points are always repeated, wasting space.

Furthermore, if the points are the same during different time-steps, can all of the unstructured grids of each time-step reference the same Points?