Attribute Closure
Attribute closure of an attribute set can be defined as set of attributes which can be functionally determined from it.
How to find attribute closure of an attribute set?
To find attribute closure of an attribute set:
- Add elements of attribute set to the result set.
- Recursively add elements to the result set which can be functionally determined from the elements of the result set.
Using FD set of table 1, attribute closure can be determined as:
(STUD_NO)+ = {STUD_NO, STUD_NAME, STUD_PHONE, STUD_STATE, STUD_COUNTRY, STUD_AGE}
(STUD_STATE)+ = {STUD_STATE, STUD_COUNTRY}
Advantages of Attribute Closure
- Attribute closures help to identify all possible attributes that can be derived from a set of given attributes.
- They facilitate database design by identifying relationships between attributes and tables, which can help to optimize query performance.
- They ensure data consistency by identifying all possible combinations of attributes that can exist in the database.
Disadvantages of Attribute Closure
- The process of calculating attribute closures can be computationally expensive, especially for large datasets.
- Attribute closures can become too complex to manage, especially as the number of attributes and tables in a database grows.
- Attribute closures do not take into account the semantic meaning of data, and may not always accurately reflect the relationships between data elements.
Functional Dependency and Attribute Closure
Fundamental ideas in database management and design are functional dependency and attribute closure. They are essential to maintaining data integrity and building effective, organized, and normalized databases.