When is the concept of weak entityused in data modeling?

The concept of a weak entity is used in data modeling when an entity cannot be uniquely identified by its own attributes alone and relies on a "strong" or owner entity for identification. Weak entities typically have a partial key that, combined with the primary key of the strong entity, creates a composite key. This is common in scenariOS where the existence of the weak entity is dependent on the strong entity, such as in relationships like "Order" and "OrderItem," where an OrderItem cannot exist without an associated Order. Weak entities are usually represented with a double rectangle in Entity-Relationship diagrams.