private Junction <User, Item> GetAssessments(IEnumerable <User> users, IEnumerable <Item> items)
        {
            var usersMap = users.ToDictionary(user => user.Name);
            var itemsMap = items.ToDictionary(item => item.Name);

            var assessments = _assessmentsSource.GetSourceEntries()
                              .Select(entry => new Assessment(usersMap[entry.Property("UserName")],
                                                              itemsMap[entry.Property("ItemName")],
                                                              entry.Property <double>("Rating")));

            var junction = new Junction <User, Item>(u => u.Name);

            junction.AddRange(assessments);

            return(junction);
        }