  AdS dynamics for massive scalar field is studied both by solving exactly the
equation of motion and by constructing bulk-boundary propagator. A
Robertson-Walker-like metric is deduced from the familiar SO(2,n) invariant
metric. The metric allows us to present a time-like Killing vector, which is
not only invariant under space-like transformations but also invariant under
the isometric transformations of SO(2,n) in certain sense. A horizon appears in
this coordinate system. Singularities of field variables at boundary are
demonstrated explicitly. It is shown that there is a one-to-one correspondence
among the exact solutions and the bulk fields obtained by using the
bulk-boundary propagator.
