Databases Reference
In-Depth Information
OLAP and SDB systems, however, have distinguishing differences. While SDBs tend
to focus on socioeconomic applications, OLAP has been targeted for business appli-
cations. Privacy issues regarding concept hierarchies are a major concern for SDBs. For
example, given summarized socioeconomic data, it is controversial to allow users to view
the corresponding low-level data. Finally, unlike SDBs, OLAP systems are designed for
efficiently handling huge amounts of data.
4.2.6
A Starnet Query Model for Querying
Multidimensional Databases
The querying of multidimensional databases can be based on a
starnet model
, which
consists of radial lines emanating from a central point, where each line represents a
concept hierarchy for a dimension. Each abstraction level in the hierarchy is called a
footprint
. These represent the granularities available for use by OLAP operations such
as drill-down and roll-up.
Example 4.5
Starnet.
A starnet query model for the
AllElectronics
data warehouse is shown in
Figure 4.13. This starnet consists of four radial lines, representing concept hierarchies
for the dimensions
location, customer, item
, and
time
, respectively. Each line consists
of footprints representing abstraction levels of the dimension. For example, the
time
line has four footprints: “day,” “month,” “quarter,” and “year.” A concept hierarchy may
involve a single attribute (e.g.,
date
for the
time
hierarchy) or several attributes (e.g., the
concept hierarchy for
location
involves the attributes
street, city, province or state
, and
country
). In order to examine the item sales at
AllElectronics
, users can roll up along the
location
customer
continent
group
country
category
province
_
or
_
state
city
name
street
item
name
brand
category
type
day
month
quarter
year
time
Figure 4.13
A starnet model of business queries.
