CHAU-DT

CHAU-DT (also stylized as CHAU DT) is a mnemonic used in the realm of data modeling and database design, specifically in the context of understanding and analyzing business requirements for database normalization. It represents a structured approach to documenting and understanding the attributes associated with an entity. Each letter stands for a key aspect of an attribute:

• C - Calculated: Indicates whether the attribute's value is derived or calculated from other attributes. A calculated attribute does not typically need to be stored directly but can be computed on demand.

• H - History: Signals whether a history of values for the attribute needs to be maintained over time. If historical data is needed, special considerations must be given to how this history will be stored (e.g., using a separate history table).

• A - Alternate Key: Denotes if the attribute serves as an alternate or secondary key for the entity. This helps identify if the attribute can uniquely identify a record within the entity, aside from the primary key.

• U - Unique: Indicates that the attribute values must be unique across all instances of the entity. This is similar to an alternate key, but an attribute flagged as "unique" might not necessarily be used as an actual key.

• D - Derived: Synonymous with Calculated; Indicates the attribute's value is derived. The use of both C and D might be due to specific conventions or dialects within certain data modeling methodologies.

• T - Triggered: Signifies that a change in the attribute's value might trigger other events or actions within the system. This consideration is important for understanding data dependencies and potential side effects of data modifications.

By systematically applying CHAU-DT to each attribute of an entity, data modelers can ensure a more thorough understanding of the data requirements, leading to better database design and normalization.