Geoscience Reference
In-Depth Information
Generalisation is considered in CollaGen as a four step operation: geo-
metry changes (e.g. area-to-point collapses), selection, cartographic and
graphic generalisation (Harrie and Sarjakoski 2002). The processes are
described as contributing to one or more of these steps and can be used
only during the right steps. The scheduling component chains these steps
according to the rules.
Figure 7:
Interactions of the scheduling component with other components and resources.
Moreover, the scheduling component provides state management to allow
local and global corrections (
Figure 8
). When a generalisation is badly
evaluated, the scheduling may cancel it and go back to previous states of
data. To allow this try/error mechanism, as in (Zhou et al. 2008), the initial
state stores the attribute data while all the geometry states are kept linked
to the generalisation pair (space/process) that led to the following step.
Figure 8:
UM=L class diagram of the state management system of the scheduling compo-
nent.
