For unidirectional relations no annotations at all are
necessary for re motion to automate the mapping to the
database in a meaningful way. re-motion simply takes a
.NET declaration in the Person class like
...
to mean "there is a unidirectional relationship between
Person and Location", and there will be a foreign key in
the Person table to its Location row in the Location table.
Things are not as easy for bidirectional relationships,
as we will see shortly.
If domain objects were not persisted in database tables
we'd have difficulty finding all Person objects belonging
to a given Location, because the .NET Location object
can't be asked for it. Since domain objects are always persisted
in a database, however, we can query the Person table for
a given location and wrap up the query in a member function
for the Location class. For bidirectional relations, re-motion
generates such queries for keeping the .NET properties in
sync with the database for you, and makes sure they work
correctly at both ends of the relation. A unidirectional
relation, however, lacks this automation in the other
direction, in this case the query for getting the persons
belonging to a location.