How do we apply structural modeling to design?

What will be an ideal response?

The ultimate mission of concrete modeling is to produce blueprints for building the information system and its components. This tasks involves both the refinement of entity classes that originate from the problem domain and the definition of design classes that serve the solution.
Design classes are not abstractions of objects that have counterparts in the problem domain. Therefore, to define their responsibilities, we must parse dynamic models, such as sequence diagrams, that identify services that the solution requires. In other words, we can define design classes by studying the needs that we discover when we re-integrate the flow of use cases with classes from analysis.