What does the ERD shown below depict?

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Question: What does the ERD shown below depict?

Option 1: An Associate entity.
- This option is unlikely because the diagram labels Building and Room as two separate entity boxes with their own attributes, and the relationship between them uses identifying markings (double lines). An Associate entity typically refers to a weakly linked or intermediary type, which isn’t indicated here by the given boxes.

Option 2: An Entity Cluster.
- An Entity Cluster usually represents a collection of entities treated as a single logical unit, often in older or specific modeling styles. The diagram, however, shows two distinct entities (Building and Room) connected by an identifying relationship, not a cluster consolidation. This makes the cluster interpretation inappropriate for the visual cues given.

Option 3: An Entity Instance.
- An Entity Instance would refer to a single occurrence of an entity (e.g., one particular Building or one particular Room). The diagram, in contrast, depicts the schema structure with keys and attributes, not a single instance of data. Therefore this option is incorrect.

Option 4: A Strong and Weak Entity.
- The key clue is the presence of an identifying relationship marker (double line) between Building and Room, which is characteristic of an identifying (owner-dependent) relationship in ER diagrams. The Building entity has its own primary key (BuildingID), while the Room side is connected via the identifying relationship, indicating that Room (or part of the room’s identity) depends on Building. This combination is the classic depiction of a strong (Building) and a weak (Room) entity pair in an ER model, where the weak entity’s primary key is partially derived from or tied to the strong entity.

Summary:
- The diagram shows two entities (Building and Room) connected by an identifying relationship, with BuildingID as a key and RoomNum as a key within Room, fitting the pattern of a strong-weak entity pair. The other options misinterpret the diagram: it’s not an associate entity, an entity cluster, or a single entity instance, but a strong and weak entity relationship.

What does the ERD shown below depict?

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