What's the best way to identify key classes and attributes in object-oriented analysis?

1 Use the problem statement

The problem statement is a concise description of the goals, scope, and context of the system or problem you are trying to solve. It can help you to identify the main actors, events, and scenarios that are involved in the system. You can use these elements as a starting point for finding the classes and attributes that represent them. For example, if you are developing a library management system, the problem statement might include actors like librarian, borrower, book, and loan, and events like check out, return, and reserve.

2 Apply the noun-verb technique

The noun-verb technique is a simple and effective way to extract classes and attributes from a textual description of the system or problem. It involves identifying the nouns and verbs in the text and mapping them to classes and attributes respectively. Nouns usually correspond to classes, while verbs usually correspond to attributes or methods of the classes. For example, in the sentence "A librarian can check out a book to a borrower", the nouns are librarian, book, and borrower, and the verb is check out. These can be mapped to classes Librarian, Book, and Borrower, and an attribute or method checkOut of the class Librarian.

3 Use CRC cards

CRC cards are a tool for collaborative modeling of classes and their relationships. CRC stands for class, responsibility, and collaboration. Each card represents a class and contains three sections: the name of the class, its responsibilities (what it knows and what it does), and its collaborators (other classes that it interacts with). CRC cards can help you to identify the key classes and attributes by brainstorming and discussing their roles and behaviors with your team members. You can also use CRC cards to check the consistency and completeness of your model by verifying the interactions and dependencies among the classes.

5 Use diagrams and notations

Diagrams and notations are useful for visualizing and documenting your classes and attributes. They can help you to communicate your model to others and to identify gaps or errors in your design. There are different types of diagrams and notations that you can use for object-oriented analysis, such as use case diagrams, class diagrams, sequence diagrams, and UML (Unified Modeling Language). These diagrams and notations can help you to show the structure, behavior, and interactions of your classes and attributes in a clear and consistent way.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?