Database Reference
In-Depth Information
4. At the end of this algorithm we obtain a path-term
f(t
RA
)
, where
f
is a path
of unary operations (different from _
), with the unique leaf
t
RA
∈
T
RA
X
: this path-term is represented in
RA
by the arrow
f
a,name,e
f(t
RA
)
.
This algorithm above defines the
normalization
function
Nrm
t
RA
→
:
:
T
RA
X
→
Mor
RA
.
5.2.2 RA versus DB Category
As we have demonstrated, all the terms of the “select-project-join+union” (SPJRU)
Σ
R
algebra which is used to define the views
q(
x
)
(introduced in basic database
concepts, Sect.
1.4
) and basic SOtgds in the inter-schema database mappings (in-
