Database Reference
In-Depth Information
connection with
=
a
R
≤
=
a
∈
W
|∀
b
b
∈
S
implies
(a,b)
∈
R
−
1
≤
λ(S)
∈
W
|∀
b
∈
S.(b,a)
∈
=
a
b
(a,b) /
S
R
−
1
≤
|∀
∈
implies
b/
∈
=
a
b
(a,b)
K
R
−
1
|∀
∈
∈
does not imply
b
φ
≤
=
a
b
(a,b)
M
|=
b
φ
R
−
1
|∀
∈
does not imply
≤
={
a
|
M
|=
a
R
−
1
≤
¬
c
φ
}=
R
−
1
≤
¬
c
φ
K
.
Thus, the modal additive algebraic negation
λ
is represented by a composition
R
−
1
≤
¬
c
of the universal modal operator
R
−
1
≤
and classic (standard) logical nega-
tion
¬
c
. Analogously,
=
a
R
≤
ρ(S)
∈
W
|∀
b
∈
S.(a,b)
∈
=
a
b
b
R
≤
∈
W
|∀
∈
S
implies
(a,b)
∈
=
a
b
(a,b) /
S
|∀
∈
R
≤
implies
b/
∈
=
a
|∀
b
(a,b)
∈
R
≤
does not imply
b
∈
φ
K
=
a
b
(a,b)
M
|=
b
φ
|∀
∈
R
≤
does not imply
={
a
|
M
|=
a
R
≤
¬
c
φ
}
=
R
≤
¬
c
φ
K
.
Thus, the modal multiplicative algebraic negation
ρ
is represented by a composition
R
≤
¬
c
of the universal modal operator
R
≤
and classic (standard) logical negation
¬
c
.
Consequently, the closure operator
Γ
=
ρλ
is represented by the composition
(
R
≤
¬
c
)(
R
−
1
≤
¬
c
).
That is, from the fact that
¬
c
R
−
1
≤
¬
c
is equal to the existential modal operator
R
−
1
≤
,
R
≤
R
−
1
≤
we obtain that
Γ
is represented by modal composition
.
In fact, it is easy to verify that the Kripke semantics of the closure operator
Γ
corresponds to
b
∀
b
,
M
|=
a
R
≤
R
−
1
≤
∀
M
|=
c
φ
implies
c
≤
≤
φ
iff
c(
b)
implies
a