1. Online analytical processing (OLAP) is a category of software technology that enables analysts, managers, and executives to gain insight into data through fast, consistent, interactive access to a wide variety of possible views of information that has been transformed from raw data to reflect the real dimensionality of the enterprise as understood by the user.
This presentation provides a good visualization of what OLAP does. In particular, it illustrates slicing and dicing data and drilldown and rollup.

2. Kinds of OLAP
ROLAP- relational OLAP using relational databases; a star schema is used
MOLAP- multidimensional OLAP using multidimensional databases
DOLAP- desktop OLAP
Other variations
OLAP comes in many “flavors.” The most common is ROLAP, because organizations typically prefer to use relational database technology. In this case, a star schema data model is used. For performance reasons, special purpose database technology, such as Essbase, is used. When this is the case, the data model is a multidimensional cube. Multidimensional vendors sometimes jokingly refer to ROLAP as SLOWLAP. Students are typically only familiar with relational databases and do not know that there are other technologies.

3. Example: Olap Usage of an Automobile Marketer
The Story
An automobile marketer wants to improve business activity. Therefore he wants to view sales figures from different perspectives.
The Data Needs
Sales by model
Sales by dealership
Sales by color
Sales over time
etc.
The dimensions in this example are the car’s model, color, and dealership.
A Question
What is the trend in sales volumes over a period of time for a specific model and color across a specific group of dealerships ?

4. Example: The Multidimensional View of the Data
Sales Volumes
Van
MOD E L
Coupe
Smith
Here the data is represented in a cube. The cells in the cube contain the number of cars sold that correspond to the specific measures of the dimensions; for example, the number of blue sedans sold at the Miller dealership.
Sedan
Clyde
Miller
Blue
Red
White
DEALERSHIP
COLOR

5. OLAP Features: “Slicing and Dicing“ the Data
Choosing a range out of each dimension:
Color: Blue and White
Model: Coupe only
Dealership: Clyde only
Sales Volumes
Clyde
Blue
White
Coupe
“Sliced and Diced“ Data
Van
MOD E L
Coupe
Smith
Sedan
The sum of the numbers in the two cubes gives the number of blue and white coupes sold at the Clyde dealership.
Clyde
Miller
Blue
Red
White
DEALERSHIP
COLOR

6. OLAP Features: Rotating the Data
Different users will require different views of the multidimensional cube – OLAP allows easy rotation of data
View of the Product Manager
View of the Account Manager
Sales Volumes
DEALERSHIP
Sales Volumes
Miller
Smith
Clyde
Van
Coupe
Sedan
MOD E L
Rotate the data cube by 90°
Van
MOD E L
Coupe
Different users may want to slice and dice the data differently, depending on their needed perspective. In the second example, the account manager is primarily interested in how the different models are selling in the various dealerships.
Sedan
Blue
Red
White
COLOR

7. Sales Volumes by Organization Dimension - three level hierarchy -
OLAP Features: Drill-Down and Roll-Up
Data can be disaggregated and aggregated along a dimension according to their natural hierarchy
Roll-Up
Sales Volumes by Organization Dimension - three level hierarchy -
Georgia
State
Region
Atlanta
Athens
Dealership
In OLAP software, drill-down and roll-up are performed with a single mouse click.
Miller
Smith
Clyde
Lucas
Gleason
Drill-Down