In general:
<set> maps to ISet
<bag> and <list> map to IList
<map> maps to IDictionary
Using <bag> will allow you to map to an IList without creating an index column. From the paragraph after the one you cite:
Quote:
A bag is an unordered, unindexed collection which may contain the same element multiple times. The
.NET collections framework lacks an IBag interface, hence you have to emulate it with an IList. NHibernate
lets you map properties of type IList or ICollection with the <bag> element. Note that bag semantics are not
really part of the ICollection contract and they actually conflict with the semantics of the IList contract
(however, you can sort the bag arbitrarily, discussed later in this chapter).
Also, I would definitely read section 15.5:
http://www.hibernate.org/hib_docs/nhibernate/1.2/reference/en/html/performance.html#performance-collections
Others may have suggestions about French language resources.