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

The natural join is equal to which product, The natural join is equal to wh...

The natural join is equal to which product? The natural join is equal to Combination of projection and Cartesian product

Optimistic concurrency control, Optimistic Concurrency Control Is locki...

Optimistic Concurrency Control Is locking the only way to stop concurrency related problems? There exist some other ways too. One such way is known as an Optimistic Concurrency

What is a primary index, What is a primary index? A primary index is an...

What is a primary index? A primary index is an index whose search key also explains the sequential order of the file.

Describe the concept of aggregation, Aggregation Aggregation is strong...

Aggregation Aggregation is stronger form of association. It represents the "has-a" or "part-of" relationship. An aggregation association depicts a complex object which is comp

What is advantage of two-way association, What is advantage of two-way asso...

What is advantage of two-way association? Two-way association advantages are following: a) Independent of the classes. b) Useful for existing predefined classes that are

Sql, sql is relationally complete-justify

sql is relationally complete-justify

Example of sequences, Example : Create a sequence named SEQSS that starts a...

Example : Create a sequence named SEQSS that starts at 105, has a step of 1 and can take maximum value as 2000.  CREATE SEQUENCE SEQSS START WITH 105 INCREMENT BY 1 MAX VA

Security-data fragmentation, Security: Data not needed by local applicatio...

Security: Data not needed by local applications is not stored at the site, therefore no unnecessary security violations may exist. But how can we carry out fragmentation? Fragm

Dbms, You are managing the following database system: • DBMS: Oracle 11g ...

You are managing the following database system: • DBMS: Oracle 11g • OS: Sun Solaris • System architecture: Web-based application using ASP.Net • Purpose of Server: HR managem

What is meant by log-based recovery, What is meant by log-based recovery? ...

What is meant by log-based recovery? The most widely used structures for recording database changes is the log. The log is a sequence of log records, recording all the update a

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