EDIT

    @ManyToMany(fetch = FetchType.LAZY)

    @JoinTable(name = "PolytomousKey_NamedArea")

    @NotNull

    private Set<NamedArea> geographicalScope = new HashSet<NamedArea>();

    @XmlElementWrapper(name = "ScopeRestrictions")

    @ManyToMany(fetch = FetchType.LAZY)

    @JoinTable(name = "PolytomousKey_Scope")

    @NotNull

    private Set<DefinedTerm> scopeRestrictions = new HashSet<DefinedTerm>();

    @XmlElement(name = "Root")