Dimensional Modelling

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Terminologies used in Multi-Dimensional Data Modeling (MDDM)

Grain

Lowest level at which members of an attribute are stored.

Hierarchies

Arranging Attributes in different levels

Ragged Hierarchies

Whichever path you may traverse the number of levels remains the same however nodes may not be present at every level(except root and leaf nodes)

Natural Hierarchies

Every child has a single parent

Dimensions

Descriptive objects used to view the fact

Role Playing Dimension

A dimension represented more than once in the fact table

Slowly Changing Dimension

one or more attributes changes over time

Members

Labels of the attributes

Attributes

Detailed Information about dimensions

Facts

Numeric values used for analysis

Types

Non-Additive fact

Not Additive across any dimension

Factless Fact

Intersection of dimensions indicative of a fact

Semi-Additive fact

Additive across most dimensions

Additive fact

Additive across all dimensions