Explain Class Based Modeling ?

Class based modeling represents the object. The system manipulates the operations. The elements of the class based model consist of classes and object, attributes, operations, class - responsibility - collaborator (CRS) models.

Classes :

Classes are determined using underlining each noun or noun clause and enter it into the simple table.

Identifying Analysis Classes :

The classes can be identified by using the below steps :

1. By performing a grammatical parse of the problem statement or use cases.

2. Classes are determined by underlining each noun or noun clause.

3. A class required to implement a solution is part of the solution space.

4. A class necessary only to describe a solution is part of the problem space.

5. A class should NOT have an imperative procedural name (i.e., a verb).

6. List the potential class names in a table and "classify" each class according to some taxonomy and
class selection characteristics.

7. A potential class should satisfy nearly all of the selection characteristics to be considered a legitimate problem domain class.

Generation Classifications for a potential class :

  • External entities : The system, people or the device generates the information that is used by the computer based system.
  • Things : The reports, displays, letter, signal are the part of the information domain or the problem.
  • Occurrences or events : A property transfer or the completion of a series or robot movements occurs in the context of the system operation.
  • Roles : The people like manager, engineer, salesperson are interacting with the system.
  • Organizational units : The division, group, team are suitable for an application.
  • Places : The manufacturing floor or loading dock from the context of the problem and the overall function of the system.
  • Structures : The sensors, computers are defined a class of objects or related classes of objects.

Attributes :

Attributes are the set of data objects that are defining a complete class within the context of the problem. For example, 'employee' is a class and it consists of name, Id, department, designation and salary of the employee are the attributes.

Defining Attributes of a Class

Attributes of a class are those nouns from the grammatical parse that reasonably belong to a class. Attributes hold the values that describe the current properties or state of a class. An attribute may also appear initially as a potential class that is later rejected because of the class selection criteria. In identifying attributes, the following question should be answered  :
  • What data items (composite and/or elementary) will fully define a specific class in the context of the problem at hand ?

Usually an item is not an attribute if more than one of them is to be associated with a class.

Operations :

The operations define the behaviour of an object. The operations are characterized into following types:

  • The operations manipulate the data like adding, modifying, deleting and displaying etc.
  • The operations perform a computation.
  • The operation monitors the objects for the occurrence of controlling an event.
  • Operations that inquire about the state of an object.

An operation has knowledge about the state of a class and the nature of its associations. The action performed by an operation is based on the current values of the attributes of a class. Using a grammatical parse again, circle the verbs; then select the verbs that relate to the problem domain classes that were previously identified.

We can understand class attributes and operation by the below diagram :


The elements of the class based model consist of classes and object, attributes, operations, class - responsibility - collaborator (CRS) models.

Class-Responsibility-Collaboration modeling :

The Class-Responsibility-Collaboration modeling provides a simple method for identifying and organizing the classes that are applicable to the system or product requirement. Class is an object-oriented class name. It consists of information about sub classes and super class. Responsibilities are the attributes and operations that are related to the class. Collaborations are identified and determined when a class can achieve each responsibility of it. If the class cannot identify itself, then it needs to interact with another class.




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