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

Equijoin, When every condition appears with equality condition (=) only. c)...

When every condition appears with equality condition (=) only. c)   Natural join (denoted by R*S) When two join attributes have the similar name in both relations. (Tha

State about the tables- DBMS, State about the Tables- DBMS Data is sto...

State about the Tables- DBMS Data is stored in columns and rows (much like a spreadsheet -main difference is how data is organised). Every row in a table is known as a record

What is ocr, What is OCR? OCR (Optical Character Recognition) is a tech...

What is OCR? OCR (Optical Character Recognition) is a technology that enables you to change different types of machine-readable documents, like scanned paper documents, PDF fil

What is meant by software and hardware raid systems, What is meant by softw...

What is meant by software and hardware RAID systems? RAID can be executed with no change at the hardware level, using only software modification. Such RAID implementations are

Describe the two alternatives for specifying structural, Describe the two a...

Describe the two alternatives for specifying structural constraints on relationship kinds? Relationship kinds have certain constraints in which limit the possible combination o

Explain degree of relation, Explain degree of relation? Degree of a Re...

Explain degree of relation? Degree of a Relation - The degree or arity of a relation is the number of attributes n of its relation schema.

Explain data dictonary on oracle, Explain data dictonary on oracle ? Da...

Explain data dictonary on oracle ? Data Dictionary - Data dictionaries are the system tables in which contain descriptions of the database objects and how they are structured.

Explain er model, Question 1 Explain ER model Question 2 What are the...

Question 1 Explain ER model Question 2 What are the characteristics of a computer provided information? Question 3 What are facts and guidelines to be considered when se

Determine the method of choosing algorithms, Determine the method of Choosi...

Determine the method of Choosing Algorithms In general, most of operations are easy and have a satisfactory algorithm since description of what is to be done also shows how i

Database Management System, Assume that you are responsible for selecting a...

Assume that you are responsible for selecting a new DBMS product for Sohar Hospital

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