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the chosen modelling for the warehouse.
The latter is closely related to those of the
sources as well as the applicability domain.
For instance, when the sources are belong-
ing to different categories and the applica-
bility requires a frequent exchange of data
between various systems, the XML repre-
sentation can be chosen for the DW.
Most of the time, types corresponding to a
component and those which are bound to it by the
relation S (an equivalence class β) are compatible.
Let T y be the set of these types. Thus, for each
equivalence class β, there exists a type t' such
that∀ t i ∈Ty, t i * t'.
In this case, the type associated with the se-
lected representative is t'. In the same way, all types
corresponding to an ordered set α of components
(according to the ordered relation I) in L' are com-
patible. Let Typ be the set of these types. Thus,
for each ordered set α of components in L', there
exists a type t' such that ∀ t i ∈Typ, t i t i * t'. Note
that t' is the type associated with the component
corresponding to the maximum of α.Example
11:The following results are obtained by applying
the algorithm using example 10:To built W 1 two
queries are generatedSource DB 1 : Q = {x 2 , x 3 ,C
ompNull 1 ,CompNull 2 ,CompNull 3 , CompNull 4 }
Source DB 2 : Q' = {CompNull 1 ,CompNull 2 , y 1 ,
y 8 , y 9 , y 10 }
To built W 2 two queries are generated:Source
DB 1 : Q = {x 5 ,CompNull 1 ,CompNull 2 {CompNull1,
l 3 , CompNull 4 }Source DB 2 : Q' = {CompNull 1 ,
y 1 , y 8 , y 9 , y 10 }
Then the structure of the DW is described
as:W 1 ={ x 2 , x 3 , y 1 , y 8 , y 9 , y 10 } and W 2 ={ x 5 , y 1 ,
y 8 , y 9 , y 10 }
Algorithm ConstrView (W)
for each k D do Q := empty view /*
initialization of an empty view*/
W:= empty viewW 0 := ( L' k
) ∩ W /*
W0 is the set of the components of
W belonging to DB k
*/
W ' := W − W 0 /* W' is the set of
the components of W not belonging
to DB k
*/
y := |W 0| /* y is the cardinality
of W' */
for each w' W do
SI w' := (S'(skl(w'), w',k)
I'(skl(w'), w',k))
/* skl function to identify the
source */
/* SIw'contains the set of the syn-
onymous components of w' in DB k
and
the set of the components of DB k
in-
cluded in w'*/
end for
for each (a 1 ,…,a y ) w' W' (SI w' ) do
Q :=W0 {a 1 ,…,a y }
/*Q contains the set of the compo-
nents to extract from DB k
A META-SCHEMA FOR
TWO POSSIBLE PHYSICAL
ARCHITECTURES
*/
Q := Q (union) Create_View(Q)/* Q
contains the partial result from
DB k
Let us note that the DW obtained by our follow-
ing integration process is independent of any
architecture. Indeed, the returned views are logi-
cal and have no information about their physical
structure. Thus, they can be implemented in any
model such as relational, object-relational or XML.
Moreover, we have the possibility to implement
our warehouse under two different architectures:
the classical star architecture (called Ws) and the
flat architecture (called Wp). In the Wp archi-
*/
end for
W := W (union) Q
end for
The procedure Create_View(Q) gives the pos-
sibility to create a view. Types are associated
to the various components of the view. These
types associated to the DBMS are used.
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