A company is consuming parts in the manufacturing of other products. Each part is either manufactured within the company or purchased from external suppliers or both. For each part, partnumber, partname is maintained. Attribute batchnumber is maintained if the consumed part is manufactured in the company. If a part is purchased from an external supplier, then the supplier name is maintained. Which of the following constraints need to be considered when modeling class/subclass concepts in ERD for the given problem?

Correct option is A

For the given problem, the Entity-Relationship Diagram (ERD) must ensure that every part (entity) is either manufactured internally, sourced externally, or both. This requires total specialization and overlapping constraints in the class/subclass relationship.
Information Booster
1. Explanation of Constraints:
· Total Specialization:
· Ensures that every part in the superclass (Parts) must belong to at least one of the subclasses (Manufactured or Purchased).
· This is necessary because the problem specifies that a part is either manufactured, purchased, or both.
· Overlapping Constraints: Allows a part to belong to both subclasses (Manufactured and Purchased) simultaneously. This is needed as the problem states that some parts can be both manufactured internally and purchased externally.
2. Other Constraints:
· Disjoint Constraint: Ensures that an entity in the superclass belongs to only one subclass. This is not applicable here as parts can belong to both subclasses.
· Partial Participation: Allows some entities in the superclass to not belong to any subclass. This is not suitable because every part must be either manufactured, purchased, or both.
3. Practical Representation in ERD:
· Superclass: Parts.
· Subclasses: Manufactured and Purchased.
· Relationships: Attributes like batchnumber (for Manufactured) and supplier name (for Purchased) are specific to the respective subclasses.
· Constraints:
· Total specialization ensures all parts are accounted for.
· Overlapping ensures flexibility for parts that fall into both categories.
Additional Knowledge
· Total Specialization: Represented by a double line from the superclass to the subclasses.
· Overlapping: Represented by an "O" in the subclass relationship.
Example: For a company managing parts:
· Part A: Manufactured only.
· Part B: Purchased only.
· Part C: Both manufactured and purchased. This setup confirms the need for total specialization and overlapping constraints.