The requirements analysis phase of the design process reveals the real world objects and their attributes that the database must represent as well as the relationships among them.
The logical database design phase formalizes the objects, or entities, and their relationships. Another primary task of logical design is normalization to ensure, for example, that the modeled entities are modified by attributes that uniquely pertain to them.
See Semantic Data Modeling and The Normalization Process for more information about logical database design.