Databases Reference
In-Depth Information
Name
Department
Salary Home Town Profile Vector
Doe
Human Resource
$63,000 Newark, NJ
10
,
001
,
10
James Other Departments $45,000 Chicago, IL
01
,
100
,
01
Robert
Human Resource
$53,000 Chicago, IL
01
,
010
,
01
Table 2.
User Profile Information
All the different profile attribute representations are concatenated to form
a profile vector, which is used to represent the profile of a mobile user. Because
the same discretization is applied to all the mobile users, the length of profile
vector is the same for all mobile users.
The idea of profile bounding vector,
PV
B
, is to represent a set of users'
profiles by applying bitwise 'OR' operations of the profile vectors. For example,
suppose that the set of profile attributes is department, salary, and home town.
Consider three profile vectors,
pv
Doe
=
10
,
001
,
10
,
pv
James
=
01
,
100
,
01
,
. Then,
PV
B
and
pv
Robert
=
01
,
010
,
01
of two users, Doe and James is
,and
PV
B
.
Given a set of
PV
B
s, hierarchical structure can be formed, also. Suppose
we have three
PV
B
s.
11
,
101
,
11
of all three users is
11
,
111
,
11
PV
1
=
11
,
011
,
10
PV
2
=
10
,
010
,
10
PV
3
These
PV
B
s can be organized in a hierarchical structure with
PV
2
and
PV
3
as the children of
PV
1
.Each
PV
B
bounds
PV
B
s of all of its children. There-
fore, the root of the hierarchy covers the set of
PV
B
s of all of its descendants.
The S
STP
-tree is constructed similar to that of
s
TPR-tree, but
PV
B
is also
updated accordingly during the insertion of new objects. Each moving object
is represented with its spatiotemporal and profile attributes. Thus, each node
in the S
STP
-tree includes a TPR and a
PV
B
for specifying the spatiotemporal
and profile conditions, respectively. When a new moving object is inserted into
S
STP
-tree, the first operation is to find a leaf node that enlarges the TPR of
the node smallest among all the other leaf nodes. After inserting the object
into the target leaf node, the TPR and
PV
B
of the target leaf node are
updated if necessary. If TPR or
PV
B
of the parent node does not enclose
all of its children as a result of inserting a new object into the leaf node,
the parent node is updated accordingly. The same operation is applied to its
parent node until the root node is reached recursively.
Given an authorization
α
and a node
N
, the following different cases of
spatiotemporal and
PV
B
=
01
,
001
,
10
relationships between
α
and
N
arise. The
PV
B
of
an authorization and a node are denoted as
α
→
and
N
→
, respectively.
•
Spatiotemporal Relationship
-
α
⊃
st
N
: Spatiotemporal extent of
α
encloses that of
N
.
