DTA(M) Database Theory & Applications
Lab 1 Tasks
Task 1: Draw & Query Entity-Relationship Diagrams
About E-R Diagram
ER Modelling is used for conceptual design
• Entities – objects or items of interest
• Attributes – facts about, or properties of, an entity
• Relationships – links between entities
Entities could represent people, places, items, events, or concepts, etc.
Attributes could represent an entity’s characteristics, e.g., name, age, etc.
Relationships could represent the relationship between two or more entities.
Guidelines: Since entities are things or objects, they are often nouns in the description Attributes
are facts or properties, and so are often nouns. Verbs often describe relationships between entities.
Textual Description of a World
Description: Our aim is to store information in a database about dogs (name, breed), their owners
(name, address, phone) and the shows that their dogs have attended over the years (recording the
specific start and end dates of each show and the show’s name). Moreover, the dogs are meant to
compete in these organised shows, where at each show the participated dogs receive a rank
(place/degree of achievement: 1: gold, 2: silver, 3: bronze, 4: none). We assume that an owner can
have more than one dog, while a dog has only one owner. Your tasks are:
• Identify the Entities, Attributes, Relationships, and potential Relationship Entities from the
provided description. Avoid redundant entities and/or relationships.
• Draw the E-R diagram based on the elements you have derived and indicate the cardinality
ratios of your relationships.