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

Define 3nf normal form, 3NF Normal Form A relation schema R is in 3NF ...

3NF Normal Form A relation schema R is in 3NF if it is in 2NF and for each FD X A either of the following is true X is a Super-key of R. A is a prime attribute of R

Normalize table 3nf , Normalize the following tables upto and including the...

Normalize the following tables upto and including the 3NF. Submit a 1 page printout of only the final set of normalized tables in Data Architect. Just use Data Architect to do the

Describe the storage structure of indexed sequential files, Describe the st...

Describe the storage structure of indexed sequential files and their access method.  Ans:   Storage structure of Indexed Sequential files and their access: To achieve fast rand

Accounting and external reporting, List the internal controls that should b...

List the internal controls that should be in effect solely because a EDP system is employed, classifing them as (1) Those controls pertaining to input of information and (2) All ot

Oracle, comparison of oracle RDBMS with MySQL

comparison of oracle RDBMS with MySQL

Describe the terms ‘database'' and ‘data warehouse'', Problem: ‘Users a...

Problem: ‘Users and Information system specialists need to spend inordinate amounts of time locating and gathering data' (Watson and Hal, 1998) Recent developments in the ar

Explain the timestamps for read operations, Timestamps For Read operations:...

Timestamps For Read operations: If TS (T) If TS (T) >= W-timestamp (Q), then the transaction T is trying to read a value of data item Q which has been written and committed

I want simple visual basic script, I want a script that will run, and updat...

I want a script that will run, and update my virtual machine's LAN settings (proxy server and port), and also re-configure the Firefox User Agent. I want a script that will run,

Appointment systems with sms and voice call feedback, Automated system for ...

Automated system for appointment with sms and call confirmation with service providers and user has to be initiate automatically. After selecting time and date to use service, s

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