UoL CS Notes
Menu

Tutorial 3

COMP107 Tutorials

Designing an ER Schema

You should identify basic components:

  • Entity types, relationship types, attributes:
    • Key attributes.
    • Cardinality and participation constrains of relationships.
    • Different entity types.

There are also weak entities such as tables or chairs. These simple objects don’t need individual identification and should be a child of the strong entity.

The lecture slides have a summary and examples of the ER diagram scheme.

Evolutionary Data Modelling

Evolutionary data modelling is an approach that proceeds in an incremental manner:

  • An initial slim model is created that satisfies some initial requirements.
  • The model is then refines in a set of iterations adding details.

Exercise

Draw an ER model to describe the data need by the conference planner app starting from users stories:

  • 3 iterations with 8 minutes each.

Task 1

  1. As a speaker, I want to upload the details of my keynote.

  2. As a speaker I want to know then my keynote is scheduled.

Screenshot 1

Task 2

  1. As a participant I want to register my attendance to a keynote.
  2. As a participant I want to book a room in a hotel.

Screenshot 2

Task 3

  1. As an organiser, I want to know which conference participants are giving keynotes.

Screenshot 3

Tutor Review

  • Speaker or not is redundant as it is implied by the fact they are presenting or not.
  • This is the same for the list of speakers. As it can be derived as a query
  • The organiser doesn’t need to be represented as they are just querying.

Final diagram after review:

ER Diagram