In some traditional methods focussed on the database, the models produced by the design process are very different from those produced by analysis. These methods require the designer to re-interpret the analysis models with tools closer to the physical design, which can sometimes be a source of confusion. If you are using this sort of method, the key is traceability - using careful, systematic methods to interpret the analysis, and making sure that you can always identify which design aspects relate to which requirements, and vice-versa.

The problem is less significant in modern object-oriented methods. Here, the design model is derived from the analysis model by a process called elaboration - the same model is progressively made more elaborate by adding design level detail:

• Design and implementation detail for the business classes identified in analysis,

• A data structure for class data you need to store (persist), and a defined mapping between the analysis level view of the data and the physical structure. You will typically also define classes which interface between the business classes and the data structure supporting complex queries, updates, and data-intensive processing,

• Implementation-specific classes such as collections to manage one-to-many relationships between classes, and Key mechanism elements such as data access and error handling. You may need to add members to business classes, and add standard supporting classes to the model,

• User service classes, which define the interface between the user and the...