The observer base type is one of two base types (the other being nobserver) for objects whose primary purpose to derive outputs from layers (directly or via other observers) outside of the “natural” computation of that object. observer is the polling type used for model responses, whereas nobserver is triggered by modification events.

some_obs description

The description of some_obs will include the additional Stalkee element.

some_obs target stalkee

Set the observed object of some_obs to be stalkee.

some_obs report 

Print the derived string state of the observed object.