Database Server Models for WMS and WFS Geographic Web Services - Geographical Information Systems: Trends and Technologies - page 166

the spatial analysis process, a new Operational Lattice of Concepts is
generated.
The semantic component represents the position in the lattice. The user
specifi es her/his semantic requirement: asking enhanced data for a specifi c
theme or indicating a theme and applying a closure operator on the graph
modeling the lattice. This allows, for each query, the localization of the
treatment(s) associated with the dynamic construction of a view into the
end-users' side. This construction is completely transparent to geographic
data servers.
In order to simplify the presentation, let us consider that the Instantiated
Lattice of Concepts (Fig. 7) also corresponds to the Operational Lattice of
Concepts. The application of the GetFeatureInfo or GetFeature operations
will be applied to an instance (of a map or an object in a given map). The
problem is now transformed into the defi nition of the data model associated
with this operation.
The GetFeatureInfo operation (from a WMS service) will require
the traversal of links typed by RLintA-M and by RLextA-A in order to
defi ne relevant attributes to be added to the initial schema. The standard
GetFeatureInfo operation provides the whole schema associated with the
result. The RLintA-A typed links are useful to determine attribute(s) to
be taken off from the initial schema. To take into account the typed links
RLintA-M and RLextA-A, the defi nition of a theme is essential. Based on
the RLintA-M link, the defi nition of the theme “Economic” will lead to
only traverse the link {“L7”}. The defi nition of the theme “Economic” with
recursive application will lead to traverse the links {“L7”} * {“L3”, “L4”}.
Based on the RLintA-A link, the defi nition of the theme “Economy” will
lead to only traverse the link {“L6”}. The source and destination attributes
involved in this link and the source attributes of the links typed RLintA-M
and RLextA-A will be considered as relevant and will be kept in the fi nal
schema. All other attributes will be removed (except the key attribute(s) if
this last one is not already present in the fi nal schema).
Table 9 illustrates an example of interactions of RL in a query based on
the class “Town” with the theme “Economic”.
To deal with the GetFeature operation (from a WFS service), we provide
two approaches. In the fi rst approach, we suggest automatically generating a
schema from the user query and to limit the result to the theme and the key
attributes. In this case, the GetFeature operation will lead to the traversal of
RLintA-A, RLintA-M or RLextA-A typed links. Within the same defi nition
of a theme (e.g., “Economic”), links {“L6”, “L7”} will be traversed. The fi nal
schema will be composed of the different attributes involved in the traversed
links. In a second approach, named standard, the user selects attributes
that should be involved in the fi nal schema. The GetFeature operation will
require the traversal of links typed “RLintA-A”. This traversal is performed