What are the key elements defining the prototypical or classical diaspora?

Shifts in the homeland–diaspora nexus: the case of decolonization

What are the key elements defining the prototypical or classical diaspora?
Examine the list of ‘common features of a diaspora’ (Table 1.1). Discuss
whether it is useful to gain an insight into a social phenomenon by
producing a list of this kind. Are there other features of a diaspora that
you think are missing?
Sökefeld argues that groups need particular opportunity structures, mobilizing
practices and frames if they are to construct themselves as diasporas. What
does he mean by these expressions and is he right?