Dependency preservation, Database Management System

Assignment Help:

Dependency Preservation

It is obvious that the decomposition must be lossless so that we do not lose any information from the relation that is decomposed. Dependency preservation is another main requirement since a dependency is a constraint on the database. If each attributes appearing on the left and the right side of a dependency appear in the similar relation, then a dependency is considered to be preserved. Therefore, dependency preservation can be checked simply. Dependency preservation is important, because as stated previously, dependency is a constraint on a relation. Therefore, if a constraint is split over more than one relation (dependency is not preserved), the constraint would be complex to meet. We will not talk about this in more detail in this unit.  You may refer to the more readings for more details. Though, let us state one basic point:

"A decomposition into 3NF is lossless and dependency preserving whereas a decomposition into BCNF is lossless but may or may not be dependency preserving."

 


Related Discussions:- Dependency preservation

Need for distributed database systems, Need For Distributed Database System...

Need For Distributed Database Systems A distributed database is a set of database kept on multiple computers that appears to applications as a one database. As a result, an app

Explain the timestamp ordering protocol, Timestamp Ordering Protocol A ...

Timestamp Ordering Protocol A timestamp is a tag that can be attached to any transaction or any data item, which indicates a specific time on which the transaction or data item

What is authorization graph, What is authorization graph? Passing of au...

What is authorization graph? Passing of authorization from single user to another can be shown by an authorization graph.

Development of an ER diagram and database implementation, i want answers th...

i want answers this assignment now if yiu can maket for me now ?

Linked list, what is difference between circular inked lust and grunded lin...

what is difference between circular inked lust and grunded linked list

Implementing a distributed database system, A distributed database is defin...

A distributed database is defined as "a collection of multiple logically interrelated database which are physically distributed over a computer network" (a) Give any three advan

Normalization, Consider a bank that has a collection of sites, each running...

Consider a bank that has a collection of sites, each running a database system. Suppose the only way the databases interact is by electronic transfer of money between one another,

Define query by example, Define Query by Example QBE is a query languag...

Define Query by Example QBE is a query language relies upon domain calculus and has two dimensional syntax. The queries are written in the horizontal and vertical dimensions of

State the data flow diagram of functional model, State the data flow diagra...

State the data flow diagram of functional model Any action initiated by transition in the state diagram can be extended into an entire data flow diagram in functional model. Th

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd