IBM Cognos Model Types

Cognos Model Types:

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

1)Relational model
2)DMR model (Dimensionally modeled relational source)

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1)Relational model:

• A relational model created from the 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.

2)DMR Model:

• This model is created from a 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 too many relationships between the levels
• A DMR model is created with 2 types of dimensions

a)Regular Dimension
b)Measure Dimension

Regular Dimension:

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 dimensions:
• 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 descend to different levels.
Ex: The highest level in the organization is the CEO.
       Level 2 is the vice president and CEO’s Executive Assistant.
The Vice Presidents have subordinates but Executive Assistants don’t have any subordinates.

Related Article: Cognos Interview Questions

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 a city
       Level 4 is street
A country such as Vatican city contains only streets no cities

4)Network hierarchies:

A member of the 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 the hierarchy is automatically defined as all level

Roles:

• 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)

Product(Regular Dimension)

Product(Hierarchy)

Measure Dimension:

Category(level 1)   

         Product_line_code(key)

         Product _lan_en(caption)

Subcategory(Level 2)

        Product_line_code(key)

        Product_type_en(caption)

Productname(Level 3)

       Product_number(key) 

       Product_name(caption)

       Product_description(Description)

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

Scope:

A scope defines a relationship between the regular dimension and the measure dimension.

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