A music library, soccer system, or course catalog can be represented in several ways.
Two useful structural models are:
Both can show kinds of things, information about them, and relationships.
They are not the same diagram.
The easiest way to distinguish them is to ask:
An ERD is primarily concerned with organized data.
For a soccer dataset, it might represent:
The ERD represents that data relationship.
A UML class diagram may show:
Player -------- Teamto express that Player and Team objects are structurally related in the software model.
The exact implementation of that software relationship is not the main concern of this FIT activity.
These questions can lead to similar-looking models without producing identical artifacts.
You can also compare both diagrams to the actual data table.
P001 | Jordan | 7 | T001
P002 | Casey | 1 | T001This shows current records and values.
Player entity
Team entity
identifiers
attributes
relationshipThis shows data structure.
Player class
Team class
typed attributes
software relationshipThis shows software structure.
Three representations can describe the same general domain from different viewpoints.
Do not assume:
Do not assume:
Do not assume:
Those conversions may sometimes be appropriate, but the model's purpose must guide the decision.
Choose an ERD when the main concern is:
Choose a UML class diagram when the main concern is:
Use the spreadsheet when the main concern is:
The strongest model is the one whose representation matches the question being answered.