entity and value objets (ddm)

[totoliso]

Hi, im trying to implement a domain driven model and i am having problems identifying "entity and value objects",i don't understand very well the concept of "identity", and life cycle.
P.Ex:
I have an objecto University that is organized in departments, and each department can have others department (sub-department).
Clearly the university is an "entity object", but departmens ...,? both are identified by its names, but 2 departments with the same name can't exists in the same university, so the identity of department is attached to the university's identity. Is department an entity object? or a value object? what is the identity?

Anyone could help me...

by

[Alarmnummer]

Hi, im trying to implement a domain driven model and i am having problems identifying "entity and value objects",i don't understand very well the concept of "identity", and life cycle.
P.Ex:
I have an objecto University that is organized in departments, and each department can have others department (sub-department).
Clearly the university is an "entity object", but departmens ...,?

I think the departments are entities as well.

An entity is an object where you are interrested in the identity and not in the properties. You girlfriend is an entity: doesn't matter if she grows a long nose, colors her hair brown, or gains ten pounds, it is still your girlfriend.

But if I replace her with an identical version, you will complain because it is not your girlfriend.

So with an entity you are interrested in the identity and not in the properties.

With a value object you are interrested in the properies. For example money: you don't care if you receive one euro coin or a different one.. as long as you get one..

[dlaidlaw]

See this, it may help...
http://lostechies.com/blogs/joe_ocam...e-objects.aspx