How to rearrange classes and operations, Database Management System

Assignment Help:

Rearrange Classes and Operations

Sometimes, the similar operation is defined across different classes and can easily be inherited from a familiar ancestor, but more often operations in several classes are similar, but not the same. By slightly altering the definitions of operations or classes, the operations could often be made to match so that they could be covered by a single inherited operation. The following types of adjustments can be made to increase chance of inheritance:

  • We will find that some operations can have fewer arguments than others. The missing arguments can be added but normally ignored. Such as, a draw operation on a monochromatic display does not require a colour parameter, but parameter can be accepted and ignored for uniformity with colour displays.
  • Some operations can have fewer arguments since they are special cases of more common arguments. In this case, you can implement special operations by calling general operation with appropriate parameter values. Such as, appending an element to list is a special case of inserting an element; here the insert point just follows the last element.
  • Same attributes in different classes can have different names. Give attributes the same name and move them to a common ancestor class, then operations that access attributes will match better. Also, watch for same operations with different names. You should note that a reliable naming strategy is significant to avoid hiding similarities.
  • An operation can be defined on many different classes in a group, but be undefined on other classes. Define it on a common ancestor class and declare it as a no-op on classes which do not care about it. For instance, in OMTool the begin-edit operation places some figures, for example class boxes, in a special draw mode to authorize rapid resizing while the text in them is being edited. Other figures do not have special draw mode, so begin-edit operation on these classes has no effect.

 


Related Discussions:- How to rearrange classes and operations

Deletion anomalies-data redundancy, Deletion Anomalies: Loss of important ...

Deletion Anomalies: Loss of important Information: In some cases, useful information may be lost when a tuple is deleted. For instance, if we delete the tuple corresponding to stu

State the meaning of object representation, State the meaning of Object Rep...

State the meaning of Object Representation  The term object representation means "to represent object with the help of objects model symbols". Implementing objects is too simp

Normalization, a project based on normalization with first, second and thir...

a project based on normalization with first, second and third normalization. There need to be a diagram also

Remove partial dependancy, , write the relational schema, and draw the new ...

, write the relational schema, and draw the new dependency diagrams. Identify the normal forms for each table structure you created

What is database utility, What is database utility? Database utility is...

What is database utility? Database utility is the interface among the ABAP/4 Dictionary and the underlying the SAP system.

The second normal form (2nf), The Second Normal Form (2NF) Definition: ...

The Second Normal Form (2NF) Definition: A relation is in 2NF if it is in 1NF and each non-key attribute is fully dependent on each candidate key of the relation. Some of th

What is d command work in the respect of qbe, What is D command work in the...

What is D command work in the respect of QBE? D: It is the command inside QBE to delete tuple(s) from the relation.

RDBMS, why data in an RDMS need to be normalised

why data in an RDMS need to be normalised

Define the basic operations of the relational algebra, Define the basic ope...

Define the basic operations of the relational algebra?     Ans: Basic operators of relational algebra are: 1. Union (∪) - Selects tuples which are in either P or Q or in bot

Nested query, what is correlation in nested query

what is correlation in nested query

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