First Normal Form Support

In a model, each entity or attribute is identified by its name. Any name for an object is accepted, with the following exceptions:

• A second use of an entity name (depending on your preference for unique names) is flagged.
• A second use of an attribute name is flagged, unless that name is a rolename. When rolenames are assigned, the same name for an attribute may be used in different entities.
• You cannot bring a foreign key into an entity more than once without unifying the like columns.

By preventing multiple uses of the same name, you are prompted to put each fact in exactly one place. However, there may still be second normal form errors if you place an attribute incorrectly, but no algorithm would find that without more information than is present in a model.

In a data model, erwin� Data Modeler cannot know that a name you assign to an attribute can represent a list of things. In the following example, erwin� Data Modeler accepts �children's-names� as an attribute name. So erwin� Data Modeler does not directly guarantee that every model is in first normal form.

However, the DBMS schema function does not support a data type of list. Since the schema is a representation of the database in a physical relational system, first normal form errors are also prevented at this level.