The static layers are represented by a grid of images
of a fixed size. These fixed-size images are referred to as tiles.
Dynamic layers are represented by a single image with a transparent
background overlaying the view.
A static layer is not supposed to change during the application
lifecycle and so can be generated once only. Typically, a static layer
is the background of the view, such as a background map.
A dynamic layer contains objects, such as symbols, that
can move and change their graphic representation.
Note
Dynamic layers must be placed on top of a static layer.
Otherwise, they are not displayed.
The advantages of a tiled view are continuous panning
and the capability of caching tiles. On the client side this avoids
a round-trip to the server and gives a better response time. On the
server side it allows the server to receive the request, retrieve
the image, and respond with the image without having to generate it.
Not having to generate the image for the response is especially advantageous
in complex applications.