It looks like you are trying to use a component for a many-to-one mapping. If you have a table of Sections that you are trying to relate with the Id then it is a many-to-one. If however you have Section and all of its properties are stored in the Articles table then component is what you want. Usually components have more than just an Id field.
An example of a component in my project is a Name Class
Code:
<component name="Name" class="Crm.Domain.Objects.Name, Crm.Domain">
<property name="FirstName" column="FirstName" type="String" length="32" not-null="true" />
<property name="LastName" column="LastName" type="String" length="32" not-null="true" />
<property name="MiddleName" column="MiddleName" type="String" length="32" not-null="true" />
<property name="DisplayName" column="DisplayName" type="String" length="32" not-null="true" />
<property name="Prefix" column="NamePrefix" type="String" length="16" not-null="true" />
<property name="Suffix" column="NameSuffix" type="String" length="16" not-null="true" />
<property name="Title" column="Title" type="String" length="32" not-null="true" />
</component>
All fields are stored in the table of the containing class. An example of a many to one.
Code:
<many-to-one name="PickList" access="NHibernate.Generics.GenericAccessor, NHibernate.Generics" class="Crm.Domain.Objects.PickList, Crm.Domain" column="PickListKey" fetch="join" />