public class R
    {

        private int Id;
        private string Name;
        private IList W;

        public R()
        {
            Name = string.Empty;
        }

        public virtual void setId(int value) { Id = value; }
        public virtual int getId() { return Id; }

        public virtual void setName(string value) { Name = value; }
        public virtual string getName() { return Name; }

        public virtual void setW(IList value) { W = value; }
        public virtual IList getW() { return W; }
   }
   
public class W
    {
      private int Id;
      private double V;

      public W(double v)
      {
          V = v;
      }

      public virtual void setId(int value) { Id = value; }
      public virtual int getId() { return Id; }

      public virtual void setV(double v) { V = v; }
      public virtual double getV() { return V; }
   }
   
CREATE TABLE W(
  Id int identity primary key,
  V float null
)

CREATE TABLE R (
  Id int identity primary key,
  Name varchar(64) null,
)

CREATE TABLE WR (
  IdR int not null,
  Position int null,
  primary key (IdR)
)
alter table WR add constraint WRFK0 FOREIGN KEY(IdR) references R(Id)

<?xml version="1.0"?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" auto-import="true" namespace="X.Classes" assembly="X">
  <class name="X.Classes.R, X" table="R" lazy="false">
    <id name="Id" access="field" column="Id">
      <generator class="native" />
    </id>
    <property name="Name" access="field" column="Name" type="String" length="64" not-null="false"/>
    <list name="W" table="WR" lazy="true">
      <key column="IdR"/>
      <index column="Position"/>
    </list>
  </class>
</hibernate-mapping>

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" auto-import="true" namespace="X.Classes" assembly="X">
  <class name="X.Classes.W, X" table="W" lazy="false">
    <id name="Id" access="field" column="Id">
      <generator class="native" />
    </id>
    <property name="V" access="field" column="V" type="Double"/>
  </class>
</hibernate-mapping>