Database Reference
In-Depth Information
Symbol
Description
Function
Returns
tg
TripleGroup
tg
.props()
Set union of property types in
tg
Set of TripleGroups
tg
.triples()
Set union of triples in
tg
TG
tp
Triple pattern
tg
.triples(
p
i
)
Triples in
tg
with property type
p
i
ntg
.root
Root of the nested TripleGroup
tg
.λ()
Structure label for
tg
based on
tg
.props()
δ(
tp
)
A triple matching the triple pattern
tp
ntg
.child()
Children of the nested TripleGroup
?
v
tp
A variable in the triple pattern
tp
(a)
δ(?
v
tp
)
A variable substitution in the triple matching
tp
(b)
Operator
Definition
TG_Load(
{
t
i
}
)
{
tg
i
|
tg
i
.triples() =
t
i
, and
t
i
is an input triple
}
TG_Proj
?
v
tp
(
TG
)
{
δ
i
(?
v
tp
) | δ
i
(
tp
)
Î
tg
i
,
tg
i
Î
TG
and
tp
.λ()
tg
i
.λ()
}
TG_Filter
Θ(?
v
tp
)
(
TG
)
{
tg
i
|
tg
i
Î
TG
and
$
δ
i
(tp)
Î
tg
i
such that δ
i
(?
v
tp
) satisfies the filter condition Θ(?
v
tp
)
}
TG_GroupFilter(
TG
,
P
)
{
tg
i
|
tg
i
Î
TG
and
tg
i
.props() =
P
}
Assume
tg
x
Î
TG
x
,
tg
y
Î
TG
y
,
$
δ
i
(
tg
x
)
Î
tg
x
, δ
2
(
tg
y
)
Î
tg
y
, and δ
1
(?
v
tp
x
) = δ
2
(?
v
tp
y
)
if O-S join, then {
ntg
i
|
ntg
i
.root =
tg
x
, δ
1
(
tp
x
).Object =
tg
y
} else {
tg
x
È
tg
y
}
TG_Join(?
v
tp
x
:
TG
x
, ?
v
tp
y
:
TGy
)
tg
.flatten()
{
tg
.triples(
p
1
)
tg
.triples(
p
2
)...
tg
.triples(
p
n
) where
p
i
Î
tg
.props()
}
ntg
.unnest()
{
t
i
|
t
i
is a non-nested triple in
tg
.root
}
È
{
(
s
,
p
,
s
´) |
t
´ = (
s
,
p
, (
s
´,
p
´,
o
´)) is a nested triple in
tg
.root
}
È
{
ctg
i
. unnest() |
ctg
i
tg
.child()
}
(c)
FIGURE 6.7
NTGA quick reference: (a) symbols, (b) functions, and (c) operators.
Search WWH ::
Custom Search