Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
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.
Figure: Derived attribute to avoid re-computation
What is meant by data-transfer rate? The data-transfer rate is the rate at which data can be retrieved from or kept to the disk.
Answer SQL Queries to extract data from data tables and questions on mapping conceptual data models into relational data model.
Need for Multiple Access Paths In practice, most of the online information systems need the support of multi-key files. For example, consider a banking database application hav
The Structured Query Language INTRODUCTION Database is an organised set of information about an entity having controlled redundancy and serves numerous applications. DBMS
what is Lossless-join decomposition
What Count function return in SQL? Count function within SQL returns the number of values. (Count function counts all the not null values in the exact column. If we need to cou
What is an ER diagram? Why is it used in Database management system (DBMS)?
er diagram on cosmetics.
Write a program within embedded SQL to associative the total trip expenses of the salesman named ‘John' for the relations. EXEC SQL BEGIN DECLARE SECTION; long total_expenses;
What is the aim of logical schema ? The main motive of the logical schema is to ensure the portability of procedures and models on various physical schemas at runtime.
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!
whatsapp: +91-977-207-8620
Phone: +91-977-207-8620
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd