Explain saving derived attributes to avoid re-computation, Database Management System

Assignment Help:

Saving Derived Attributes to Avoid Re-computation  

As discussed, "redundancy means duplication of exact data". But, if multiple copies of same data are present in the system, then it can increase chance of availability of data, but the problem of computing overhead is also associated with it.

To overcome this difficulty we can "cache" or store the redundant data in its computed form and classes or objects might be defined to retain this information. The class which contains cached data must be updated if any of objects that it depends on are changed.

Figure shows use of derived object and derived attribute in OMTool. Each class box contains an ordered list of operations and attributes, each represented as text string (left of diagram). Given the location of the class box itself, the location of each attribute can be computed by adding up the size of all the elements in front of it. Since location of each element is required frequently, location of each attribute string is computed and then stored. The region containing entire attribute list is also computed and saved. In this way, you can avoid the testing of input points against the attribute text element. It is shown in the right side in Figures. If a new attribute string is added to list, then locations of the ones after it in list are simply offset by size of the new element.

 

728_Derived attribute to avoid re-computation.png

                                                                       Figure: Derived attribute to avoid re-computation


Related Discussions:- Explain saving derived attributes to avoid re-computation

Determine bcnf-dcnf and key relation, (A) For the relation; CarSales (R...

(A) For the relation; CarSales (RegNo, BuyerName, Address, SalesPerson, Make, Model, Commission) The following functional dependences hold, RegNo _ID à Make, Model Reg

Explain the fourth normal form, Fourth Normal Form (4NF) When attribut...

Fourth Normal Form (4NF) When attributes in a relation have multi-valued dependency, further Normalization to 4NF and 5NF are needed. Let us first find out what multi-valued d

Concurrency control, discuss the purpose of the concurrency control?

discuss the purpose of the concurrency control?

Data replication, Data Replication "If a relation R has its copies kept...

Data Replication "If a relation R has its copies kept at two or more sites, then it is considered replicated". But why do we replicate a relation? There are several advan

Oracle, List and explain the memory constructs of the Oracle 12c databases?...

List and explain the memory constructs of the Oracle 12c databases?

What are the benefits of decomposing a system, What are the benefits of dec...

What are the benefits of decomposing a system? The benefits of decomposing a system into subsystems are that after decomposition, each individual component become smaller and e

Project, I need help in doing my dbms project

I need help in doing my dbms project

Relational database management, For this application, we will consider IBM ...

For this application, we will consider IBM DB2 catalog data (i.e., metadata) for IBM's enterprise-class servers running the z/OS (formerly OS/390 or MVS) operating system.  One of

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