The definition for an internal state of the system is given in class models. The class modelling elements include classes themselves, attributes and operations of classes, associations, aggregation and composition, and generalization. A class diagram provides a combined visual representation for these modelling elements. Class models can lead to discovery of overlooked use cases. Following the approach taken in finding actors and use cases, construct a table that assists in finding classes from the analysis of function requirements. Think what access paths between these classes are required by the use cases. Add associations and compositions to the class model. Consider your model and think how you can extract any common attributes in the existing classes into a higher-level class. Add generalizations to the class model.
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