Information Technology Reference
In-Depth Information
type
D, C, V, Res Typ, Res VAL , N
S=H
DB
Stg
Stack
Stack = DCV
H=(D
m
(C
m
(V
m
(M
H
Q
O))
Q
O)
Q
O)
Q
O
M=L
F
F=Data
!
Data
DB = L
m
Data
Stg = N
m
(Res VAL
Stack
DCV
On)
DCV = D
j
D
C
j
D
C
V
OTup = ((A
C
)
Res Typ)
Q)
!
OFct = (((VAL
Data
)
j
Res VAL )
O=On
m
OTyp
OFct
Q
Yet even the formulas may have to be narrated | and that was done in the
three Sections 6.1|6.3.
6.5
Data Sharing, Viewing and Gluing
The indirect reference, via M, in the database DB to the geographic information
system or demographic information system Data is provided for a number of
reasons:
Local Layering:
For each layer descending M's (i.e. L's) may refer, in fact, to
\overlapping" (probably embedded) Data. At one (say an \upper") layer an L
refers to a \large" spatial area (or a large census table), whereas at a \lower"
the L may refer to an \smaller" area probably properly contained in the \larger"
area. The View functions F therefor serve to sub-locate the right sub-Data!
More concretely: If a domain name at an \upper" layer is `Europe' then
through the recursive decent through some (C,V) designated H we get the do-
main names: `Denmark', etc. The \upper" L designated perhaps a map of Eu-
rope, whereas the \lower" should designate a map of Denmark.
Quite specically: In a Cartographic & Cadestral Service the maps of a city
may be in the database DB as a set of \gluable" sub-maps. These may cover
areas not related to administrative or other domain nameable entities. The vari-
ous layers now \zoom" in on successively \smaller", but administratively \well-
rounded" areas. The purpose of the view functions are to collect from one or
more sub-maps Data covering the located area and \glue" it together.
Global Distribution:
The database may itself be distributed | and across the
globe! Now L's (with their F's, i.e. the M's) also contain for example
Internet
information (etc.) so that the Data can be located \in somebody else's database"!
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