question about Schema Component Constraint: Particle Valid (Extension)

Hej,

the second part of Schema Component Constraint: Particle Valid (Extension) 
says:

E's {min occurs}={max occurs}=1 and its {term} is a sequence group whose 
{particles}' first member is a particle all of whose properties, recursively, 
are identical to those of B, with the exception of {annotation} properties.

What exactly are the properties of the particles that must be equal?

Ciao,
Tobias