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);
}