Databases Reference
In-Depth Information
•
Case 2:
Else if (
α
is disjoint with
N
)
∨
(
α
→
is disjoint with
N
→
)is
true, overlaying process is stopped.
Case 3:
Else if (
α
overlaps
N
)
(
α
→
overlaps
N
→
) is true, the over-
laying strategy is different depending on the level of
N
.If
N
is a non-leaf
node, traversal to each of
N
's children node
C
is done, and the same com-
parison between
α
and
C
is performed. If
N
is a leaf node,
α
is overlaid
on
N
.
•
∨
α
1
⊃
st
α
1
N
1
,N
2
,N
3
V
1
V
2
V
3
α
1
→
∩
p
α
1
→
⊃
p
α
1
→
ⓧ
p
→
N
1
N
2
N
3
N
1
α
1
α
1
→
V
1
V
2
V
3
V
1
V
2
V
3
→
N
3
N
2
V
1
V
2
V
3
V
1
V
2
V
3
V
1
V
2
V
3
V
1
V
2
V
3
Fig. 4.
Authorization Overlaying Process in S
STP
-tree
Figure 4 presents the overlaying process in the S
STP
-tree. It shows that a
node
N
1
is a root node of the tree, and
N
2
,
N
3
are the children nodes of
N
1
.
Consider an authorization
α
1
to be overlaid on the S
STP
-tree.
α
1
cannot be
overlaid on the node
N
1
since
α
1
∩
p
N
1
, which belongs to the case 3 above.
Therefore, we need to traverse down to
N
1
's children nodes
N
2
and
N
3
.The
first traversal path is to
N
2
,and
α
1
can actually be overlaid on
N
2
because
α
1
⊃
st
N
2
and
α
1
⊃
p
N
2
, which is case 1 above. Another traversal path to
N
3
is stopped because
α
1
⊗
p
N
3
, which belongs to the case 2 above.
The user access request evaluation process is very similar to that of
s
TPR-
tree. A user request typically is of the form of requesting objects in the area
of interest that satisfy a certain profile criteria. For example, a merchant
is interested in sending promotion deals to mobile customers who are near
a mall and whose salary is greater than $52,000. However, such promotion
deals should be reached to only to the customers who are willing to reveal their
salary information to that merchant (specified in the authorization) to receive
the promotion deal. In the following, how such a request can be processed is
discussed while enforcing the specified authorizations.
We discuss the request type of SMR only because the application of
PV
B
to the request type of MSR is straightforward. Observe that SMR includes
spatiotemporal extent condition as well as profile condition. The profile con-
dition of SMR is represented as
PV
B
and denoted as
SMR
→
. The evaluation
process starts with the root node by comparing the spatiotemporal extents
