group = {                                        product_field = {
    id : integer                                     product_id : integer
    name : string : not null                         field_id : integer
}, {                                                 value : string not null
    id : primary key                             }, {
    name : unique key                                product_id, field_id : unique key
}                                                }, {
                                                     product.id <- product_id
division = {                                         field.id <- field_id       
    id : integer                                 }                   
    group_id : integer                                    
    name : string : not null                     product = {
}, {                                                 id : integer    
    id : primary key                                 ...  
    group_id : key                               }, {
    name : unique key                                id : primary key
}, {                                                 ...
    group.id <- group_id                         }
}

field = {
    id : integer
    division_id : integer
    name : string : not null
}, {
    id : primary key
    division_id : key
    name : unique key
}, {
    division.id <- division_id
}
