Types of models: Relational/DMR model
Types of models:
A model is a collection of metadata that includes physical information and business information for one or more data sources. (Have a quick glance at Define the model in the project)
There are 2 types of models defined in cognos10.1 BI
2)DMR model (Dimensionally modeled relational source)
- A relational model created from relational database as a source
- A relational model supports ROLAP and users cannot perform multi dimensional analysis such as drill up and drill down
A multi dimensional analysis is a technique to modify the data so that users can view the data at different levels of details
The following are the multidimensional techniques
a)Drill down: It is a process of navigating the data from highest level to lowest level details. A user can view the detailed information.
b)Drill up: It is a process of browsing the data from lowest level to highest level. A user can view the summary data.
- This model is created from relational model as a source
- A DMR model is created with the hierarchies
- A hierarchy is an ordered series of related dimensions grouped together to perform multidimensional analysis
- There should be one to many relationships between the levels
- A DMR model is created with 2 types of dimensions
A dimension is a broad group of descriptive data about the major aspects of a business.
A regular dimension contains descriptive and business key information and organizes the information in a hierarchy from the highest level of granularity to the lowest
- It usually contains multiple levels
- Each level requires KEY and CAPTION Hierarchies for regular dimension:
- A hierarchy is an ordered list of levels
- A regular dimension is created with hierarchies
Following are the types of hierarchies:
1) Balanced hierarchy:
Each path in the balance hierarchy descends to the same depth.
Ex: The highest level is productline
2nd level is the productype
3rd level is the product
2) Unbalanced hierarchy:
The branches in the unbalanced hierarchy descends to the different levels.
Ex: The highest level in the organization is CEO.
Level 2 is the vice presidents and CEO’s Executive Assistant.
The Vice Presidents have subordinates but Executive Assistant don’t have any subordinates.
3) Ragged Hierarchies:
At least one path in the hierarchy skips at least one level.
Ex: Highest level could be continent
Level 2 is County
Level 3 is city
Level 4 is street
A country such as Vatican city contains only streets no cities
A member of hierarchy has more than one parent
Levels for regular dimension:
- A level is a collection of attributes typically of common granularity.
- Each level needs an item that is defined as a KEY and another item that is defined as a CAPTION
- The first level of hierarchy is automatically defined as all level
- A role defines what appears in the member tree.
- A role determines how to present the data to the users.
Regular dimension— Hierarchy— Levels—- Attributes— Roles(Key,Caption)
It is defined as a collection of facts.
You can create a measure dimension for one or more query subjects that have a valid relationship between them.
Model measure dimensions should be composed of only quantitative items.
Ex: Key performance indicators like Sales, Net profit
A scope defines a relationship between regular dimension and measure dimension.