An Instance Specification is a template in a Class Diagram that represents an individual instance of a class or a specific occurrence of an object in the system. Instance Specifications are used to provide concrete examples of how objects of a particular class might look like with specific values assigned to their attributes. They can be helpful for illustrating the behavior of the system in specific scenarios or for testing purposes.
Example: In a Class Diagram for a system that manages customer orders, you might have a class called “Order” with attributes like “orderId”, “customerName”, and “orderTotal”. To demonstrate how an instance of the “Order” class would look like, you can create an Instance Specification with specific values for these attributes, such as “orderId: 1001”, “customerName: ‘John Doe'”, and “orderTotal: 150.50”. This instance represents a particular occurrence of an order in the system with the given attribute values.