The Kimball model, also known as the dimensional modeling approach, is a popular data architecture used in data warehousing and business intelligence environments. It was introduced by Ralph Kimball and focuses on organizing data into a dimensional model, which is optimized for analytical reporting and analysis.
Here are the key components and characteristics of the Kimball model data architecture:
- Dimensional Modeling: The Kimball model uses a dimensional modeling technique to design the data model. It organizes data into two main types of tables: fact tables and dimension tables.
- Fact Tables: Fact tables contain the numerical measures or metrics that represent the business processes or events being analyzed. Each row in the fact table corresponds to a specific instance of the event or process and contains foreign keys that link to dimension tables.
- Dimension Tables: Dimension tables provide descriptive attributes related to the business processes or events. They contain the textual or descriptive data that provides context to the measures in the fact table. Dimension tables are relatively wide and shallow, with fewer rows compared to fact tables.
- Star Schema or Snowflake Schema: The Kimball model typically adopts a star schema or a snowflake schema for organizing the tables. In a star schema, the fact table is at the center, surrounded by dimension tables radiating outwards. In a snowflake schema, dimension tables are further normalized into multiple related tables.
- Conformed Dimensions: Conformed dimensions are dimensions that are shared across multiple fact tables. They provide consistency and enable easy integration of data across different areas of analysis within the data warehouse. Conformed dimensions help ensure data consistency and accuracy across the organization.
- Slowly Changing Dimensions (SCDs): Slowly Changing Dimensions refer to the dimensions that change over time but at a relatively slow rate. The Kimball model provides techniques for handling different types of slowly changing dimensions, such as Type 1 (overwrite), Type 2 (add new row), and Type 3 (add new attribute).
- Aggregations: The Kimball model supports the creation of pre-calculated summary or aggregate tables to improve query performance. Aggregations store summarized data at different levels of granularity, allowing for faster retrieval of results for common analytical queries.
- Business Processes and Grain: The Kimball model focuses on identifying and modeling key business processes. It defines the grain, which represents the level of detail or transactional level at which data is captured. The grain is a critical concept in dimensional modeling as it determines the level of analysis and reporting possible.
- ETL Processes: Extract, Transform, Load (ETL) processes are fundamental to the Kimball model. ETL processes extract data from various source systems, transform it into the desired dimensional model structure, and load it into the data warehouse.
Overall, the Kimball model emphasizes simplicity, ease of use, and understandability for business users. It aims to provide a flexible and intuitive data architecture that supports efficient querying and analysis in a data warehousing environment.