How to add a new triple into a named graph in TDB?

[Wang Dongsheng]

Hi, all
   It confused me a lot that when I maintain a named graph.

   I stored many named graph in TDB, I can get the named graph by
dataset.getNamedModel("model name"); or delete the named model by
dataset.removeNamedModel("").

   But when I want to add a new triple, into the named model, it does
not work. For example, Model model = dataset.getNamedModel("model
name"); model.add("a statement");

   The statement is not found in the named model or even in the default model.~