Extracting an object diagram to a class diagram

Below, is the mapping of class diagram to object diagram correct? I can not seem to find a useful tutorial on object diagrams anywhere!

Here is the image

Technically Your Object Diagram is True

Object diagrams are not used much as class diagrams. [ Although we are doing Object-Oriented not Class-Oriented Design-Programming, that is irony :-) ]

Object Diagram is simple : Just show objects and the connections between them.

And All Diagrams Should Have Purpose

Why to use Object Diagram?

• To make things more explicit? Such as what DataItem can be in real life?

• Or you may start with object diagram, then find-discover classes from those objects?

Why you map Class Diagram to Object Diagram?

Ask, what I will get from drawing object this diagram,if you have good benefit-reason, Then you are on the right track. Go on... :-)

For More Info:

Object Diagrams are simple. Just look at the book:

The Elements of UML 2.0 Style by Scott Ambler

[ Chapter 13: UML Object diagram guidelines (3 guidelines) ]