Final answer:
In an E/R (Entity-Relationship) model, attributes are indeed associated with both entity sets and relationship types, which means option a. is true. Other options have conditions that are not necessarily accurate descriptions of the E/R model.
Step-by-step explanation:
The E/R model, which stands for Entity-Relationship model, is a conceptual tool for designing databases. Looking at the options provided in the question:
- Attributes are associated to both entity sets and relationship types: This statement is true. In an E/R diagram, attributes can be associated with both entities and relationships. For example, an entity 'Person' may have attributes like 'Name' and 'Age', while a relationship 'Employment' connecting 'Person' and 'Company' entities might have 'Salary' as an attribute.
- Attributes cannot have the same name in the same entity set: In general, within the same entity, attributes should have unique names to avoid confusion. However, this statement does not hold true if interpreted as an absolute rule for every case in the model, such as when dealing with different entity sets or between entity sets and relationship types.
- Attributes are very simple types, e.g., integers or character strings: While it is true that attributes often are simple data types like integers or strings, this statement is misleading because attributes can also be more complex data types, and this is not an inherent restriction of the E/R model.
- All of the others: This is not true since not all the provided statements are correct.
Therefore, the correct answer is a. Attributes are associated to both entity sets and relationship types, as they play a crucial role in defining the characteristics of both entities and the relationships between them in an E/R model.