I would like to know whether it a migrant group or host society to determines whether an individual migrant is assimilated, integrated, marginalized or separated?
That's an interesting question. I imagine that its difficult to find a complete answer because there are many authors, organizations, and agents that would give their own opinion based on specific (local, time, culture) experiences. So, if you intend to study a definition, maybe it would be a good idea to research different points of view about this issue.
I will give you some suggestions for reading, hope it helps you.
Integrating refugees What works? What can work? What does
not work? A summary of the evidence, second edition.
Thanks for this interesting topic. I think there should be a good discussion about this topic.
First of all, as a matter of principle, I think the migrant person must be able to decide whether he/she has been assimilated or neglected. In reality, this is not always the case. The issue is complex. So I think the question can be handed over to researchers who can examine the data, the situation in the field and then decide on this issue.