Data Modelling

1
Data Modelling

• Tutorial 1, DT211 Stage 2

2
Modelling data

• All real-world things, or Entities can be
  described.
• Write a description of the following items
• 4 Books you know
• 4 Students you know
• 4 Houses you know
• 4 College courses you know

3
Relevant data

• When modelling real-world things, we need to
• Decide what type of data is important
• Decide how that data can be represented
• Formulate a model for the entity.
• Return to your descriptions
• Decide what type of data you have described
• How can it be represented.
• Formulate a model for it.

4
Data abstraction

• When looking at a group of items, it is often
  possible to categorise them.
• What are these?

5
What are these?
6
And what are these?
7
Abstraction

• This is where you group entities by their similar
  attributes
• Even within the grouping, it is obvious that each
  entity is an individual
• What are the common attributes of these things
  (entities)?
• What are the differences between them?
• Can you put the differences under headings, so
  that they can be compared?

8
Exercise

• Pick out attributes of the pictures described in
  the previous slides.
• Go back to the second slide. Pick out attribute
  headings that you would use to describe a
• Book
• Student
• House
• course