- ERD is a structral and static representation of the system = not expected to change later
- Memories in DFD are to be found in ERD
- ERD only represent objects (and their attributes) that we do store information about (unlike UML Class diagram)
- Go back to the verbal description of your system to seek objects mentioned by your client - do we store information about them?
- Data fields in your Screen wireframes must be consistent with entity sorts and their attributes in ERD
Domain Understanding and Modeling
Week 6 - Entity Relationship Diagram
- Purpose of making ERD
- ERD Notation
- How to make ERD
- Normalization rules - 1st to 3rd
Slides in English:
Chyba: Odkazovaný objekt neexistuje nebo nemáte právo jej číst.
https://is.muni.cz/el/fi/podzim2024/PA116/um/en/DUM_07_ERD-ENG.pdf
Recorded lecture in Czech:
Chyba: Odkazovaný objekt neexistuje nebo nemáte právo jej číst.
https://is.muni.cz/el/fi/podzim2024/PA116/um/vi/84982684/
Seminar briefing in English:
Chyba: Odkazovaný objekt neexistuje nebo nemáte právo jej číst.
https://is.muni.cz/el/fi/podzim2024/PA116/um/seminar_briefings/Data_Dictionary___ERD.mp4
Things to remember regarding ERD
How to model inheritance in ERD?
Things to remember regarding Data dictionary
- Data dictionary is a different way how to store information about the data we collect
- DD reminds of grammar (check slides to refresh the notation)
- Usually, it is more understandable for layman than ERD
- We do it to make sure what people mean when they mention some object (e.g. a "client" mentioned by an accountant department may not be the same as "client" mentioned by sales department --> does it have the same attributes?)
Seminar tasks:
- Create a data dictionary for 5 objects [1 pt]
- Create an ERD for your system [4 pts]
Do not forget
- Apply 1st - 3rd normalization rules
- Get rid of M:N relationships
- Get rid of 1:1 relationships