Final answer:
5NF and DKNF refer to advanced stages of normalization in database design that are not commonly used as they require complex structures, which are often not necessary for many practical scenarios. They are aimed at eliminating redundancy and update anomalies, but may not exist in every relation or be used in every normalization process.
Step-by-step explanation:
The terms 5NF (Fifth Normal Form) and DKNF (Domain-Key Normal Form) refer to specific stages in the normalization process of a relational database design. Both are advanced stages of normalization that are not commonly used in most practical database design scenarios. 5NF is reached when a database is structured in such a way that it is immune to redundancies caused by join dependencies. On the other hand, DKNF is achieved when a database has no modification anomalies and every constraint on the database is a logical consequence of the domain constraints and key constraints.
In practical terms, 5NF and DKNF are not likely to exist in every relation, as not all databases require such complex structures to ensure data integrity and minimize redundancy. Furthermore, they are not commonly used in database design primarily because reaching these forms can be complex and require substantial effort, which may not be justified by the benefits in many situations. Considering the normalization process, while these forms are part of the theoretical framework of normalization, they are not regularly used in the normalization process for everyday database applications. Nevertheless, it is incorrect to say that they are used to eliminate redundancy; in fact, reaching these higher forms of normalization is specifically aimed at reducing or eliminating redundancy and update anomalies in a database system.