First the danger and the security zones must be defined. This is done by using the
well-known GIS base function "Buffer", which is available as a WPS process. In
order to calculate the number of persons to be evacuated, population numbers are
available per building block. The building block information has to be clipped with
the danger zone and then the population information has to be summed up. This is
achieved by using the WPS process PolygonIntersectsPolygonJoinAggregation.
Additionally the number of persons within the security zone who are inside buildings
of special interest must be calculated. These building and respectively the number of
people inside are provided by a WFS. Using the WPS process PointInPolygonJoin all
the buildings of special interest inside the security buffer zone are determined. Then,
by using the WPS process Aggregation, the number of persons inside those buildings
is calculated [14] (we assume here that the needed data is available or can be found
through a search in the CSW and retrieved from a WFS). On top of this, a WFS