Concepts in relational database design referat

The relation database design is based on the relational concept approach which describes the information in the manner of predicate logic and truth statements. The relation between this concept and the relational database design is the following: when needing stored information in a database, information about selection criteria must be provided. These are in the form of a logic model, underlying truth axioms about the world. Taking the logic model into consideration, the relational database provides derived truths to the requester in the form of the needed information. For allowing a logic communication format between requester and requestee the relational model is described through a series of terms, like relation, tuple, domain and database. Their definition is given below:

o Relation : it refers to a truth predicate, that is delivered with attributes
o Attribute: identifies the part in the relation and specify also the domain from which it comes from
o Domain: it specifies data type
o Tuple: is truth statement in the context of a relation; the tuple is composed by a series of attributes
o Relation value: is a composition between a heading relation and a set of tuples
o Relational variable: is referred by a single relation value at any point in time, but it can change its value, depending on the input. Also referred as table
o Database: is a collection of relation variables, forming a definite informational model; its state can be changed by modifying the relation variables

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