Information Technology Reference
In-Depth Information
6.6
A Relational View
In the presentation of the Federated GIS+DIS given so far we may have left the
reader with the impression that access to the global information is through a
strict sequence of triples of domain, then type and nally version identiers.
We now lift this seeming restriction to allow for a relational access approach.
Instead of the (d,c,v)-list view so far proposed and formalized:
type
H=D
m
(C
m
(V
m
(M
H
:::
)
:::
)
:::
)
:::
we instead suggest a relational view:
type
rH
RelH = (rH
H)
-set
H=D
C
V
rH
O
Q
rH is like a relation tuple identier.
It is easy to see that any relation RelH can be mapped into either of:
type
H=D
m
(C
m
(V
m
(M
H
:::
)
:::
)
:::
)
:::
H
0
=C
m
(D
m
(V
m
(M
H
:::
)
:::
)
:::
)
:::
H
00
=V
m
(C
m
(D
m
(M
H
:::
)
:::
)
:::
)
:::
etc.
Given a relational representation the user can then determine, at any layer to
view the information base, which ordering of the (d,c,v)'s to select | and the
system can respond by presenting the tables as selected.
Initially the system \sets" the hierarchy layer (H), for example: rhr
0
. Subse-
quently the user sets, in sequence two of either of the D, C, or V \buttons".
7 A GIS+DIS{based DSS for SD
In the decision support system for sustainable development we dealt with re-
sources, with representations of resources, with attributes and indicators, and
with functions over resources and resource representations, attributes and indi-
cators.
7.1
Spatial Resource Maps and Filters
With respect to spatially related resources, we do not record the individual
resources or their representations. Instead we typically, when it comes to for ex-
ample environmental resources, record highly complex aggregations of numerous
such resources in the form of for example remotely sensed images.
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