Search results
Results from the WOW.Com Content Network
In database design, a lossless join decomposition is a decomposition of a relation into relations , such that a natural join of the two smaller relations yields back the original relation. This is central in removing redundancy safely from databases while preserving the original data. [ 1 ]
A decomposition of R into (X, Y) and (X, R − Y) is a lossless-join decomposition if and only if X Y holds in R. Every FD ( functional dependency ) is an MVD (multivalued dependency) because if X → {\displaystyle \rightarrow } Y, then swapping Y's between tuples that agree on X doesn't create new tuples.
The problem remains NP-complete even if a prime factorization of is provided. Serializability of database histories [3]: SR33 Set cover (also called "minimum cover" problem). This is equivalent, by transposing the incidence matrix, to the hitting set problem. [2] [3]: SP5, SP8 Set packing [2] [3]: SP3
In database theory, a join dependency is a constraint on the set of legal relations over a database scheme. A table T {\displaystyle T} is subject to a join dependency if T {\displaystyle T} can always be recreated by joining multiple tables each having a subset of the attributes of T {\displaystyle T} .
Object-oriented decomposition breaks a large system down into progressively smaller classes or objects that are responsible for part of the problem domain. According to Booch, algorithmic decomposition is a necessary part of object-oriented analysis and design, but object-oriented systems start with and emphasize decomposition into objects. [2]
Database normalization is the process of structuring a relational database accordance with a series of so-called normal forms in order to reduce data redundancy and improve data integrity. It was first proposed by British computer scientist Edgar F. Codd as part of his relational model .
Fourth normal form (4NF) is a normal form used in database normalization. Introduced by Ronald Fagin in 1977, 4NF is the next level of normalization after Boyce–Codd normal form (BCNF). Whereas the second , third , and Boyce–Codd normal forms are concerned with functional dependencies , 4NF is concerned with a more general type of ...
Object–relational impedance mismatch is a set of difficulties going between data in relational data stores and data in domain-driven object models. Relational Database Management Systems (RDBMS) is the standard method for storing data in a dedicated database, while object-oriented (OO) programming is the default method for business-centric design in programming languages.