We have the code below. The association is wrong because there is no 'Notitie' on the FactuurEntity. There is a 'NotitieId' present. The association is NOT produced in the DB. The RootEntity contains the Id of the entities and has a HierachyRoot attribute and a key generator.

using Xtensive.Orm;

namespace Fortrus.DataWarehouse.Model
{
    [TableMapping("Notitie")]
    [Index("NotitieId", Name = "IndexNotitieNotitieId")]
    public partial class NotitieEntity : RootEntity
    {
        [Field(Nullable = false)]
        public long NotitieId { get; set; }

        [Association(OnOwnerRemove = OnRemoveAction.Cascade,
             OnTargetRemove = OnRemoveAction.Clear, PairTo = "Notitie")]
        public EntitySet<FactuurEntity> FactuurList { get; set; }
    }
}

using System;
using Xtensive.Orm;

namespace Fortrus.DataWarehouse.Model
{
    [TableMapping("Factuur")]
    [Index("FactuurId", Name = "IndexFactuurFactuurId")]
    [Index("NotitieId", Name = "IndexFactuurNotitieId")]
    public partial class FactuurEntity : RootEntity
    {
        [Field(Nullable = false)]
        public long FactuurId { get; set; }

        [Field(Nullable=false)]
        public long NotitieId { get; set; }
    }
}