I agree with Jasper. He explains clearly when you need a third entity
between two entities having a ManyToMany relation. But I always put much
emphasis on giving the right names to those entities, otherwise your model
becomes very messy. RelationType indeed looks better to me than Relation;
but there might be other even more descriptive names.
On Tuesday, 1 April 2014 10:48:22 UTC+2, Jàπ (Jasper N. Brouwer) wrote:
>
> About the 3rd point:
>
> The `Relative` entity in this case is representing the ManyToMany
> association between 2 `User` entities. This associations needs additional
> data, so it becomes a OneToMany/ManyToOne association (hence the entity).
>
> I do agree that the name `Relative` might not be the best choice. I agree
> that it's the User that's a relative of another User. So maybe it could be
> called `Relation`, because the association represents the _relation_
> between 2 Users.
>
> I think the current `Relation` entity should be named `RelationType`, as
> it's metadata about the `Relation` (currently named `Relative`). If I
> understood correctly it's going to contain values like "brother/brother"
> and "father/son".
>
> So the complete picture would look like this:
>
> User <- OneToMany -> Relation <- ManyToOne -> User
>
> Relation <- ManyToOne -> RelationType
>
>
> A final suggestion:
>
> Give `Relation` the properties `$id`, `$user`, `$relatedToUser` and
> `$relationType`.
> You have a `invitedby_id` in the table, but I'm not sure this is needed. I
> think you want to store the user that initiated the relation, but that's
> always the user in `$user` (never `$relatedToUser`), I'll get to that in a
> moment.
>
> Have `RelationType` contain values like "father" and "son", not
> "father/son".
>
> Now, say you have User(1) and User(2), and $user1 wants $user2 to be his
> son. You can create a `Relation` entity like so:
>
> $id = 123
> $user = User(1)
> $relatedToUser = User(2)
> $relationType = RelationType("son")
>
> Now you app knowns User(2) is the son of User(1) (from User(1)'s
> perspective), but it doesn't know that User(1) is the father of User(2)
> (from User(2)'s perspective). If you do want your app to know the latter,
> create a second relation:
>
> $id = 456
> $user = User(2)
> $relatedToUser = User(1)
> $relationType = RelationType("father")
>
> If you always want to have these 2 `Relation` entities for a single
> father/son -like relation, have something like a RelationManager service
> create (and remove) those entities.
>
> The reason I suggest using 2 `Relation` entities is because using this
> throughout your app will be much easier. When you need to know all the
> relatives of User(1), you can simple query all `Relation::$relatedToUser`
> users where `Relation::$user` is User(1).
> When using only one `Relation` entity, you would have to query for all
> `Relation::$relatedToUser` users where `Relation::$user` is User(1) OR all
> `Relation::$user` users where `Relation::$relatedToUser` is User(1).
>
> I hope this helps!
>
> --
> Jasper N. Brouwer
> (@jaspernbrouwer)
>
>
> On 1 Apr 2014, at 10:06, Herman Peeren <[email protected] <javascript:>>
> wrote:
>
> > On Tuesday, 1 April 2014 07:12:49 UTC+2, Swapna V wrote:
> > (...) that model could be improved, definitely would like to get
> suggestions (...).
> >
> > First thing I would do: to name all entities in singular, not plural.
> You don't have a "Users" entity, but a User. That its data is based on a
> users-table (named in plural) is OK, but the entity itself is a User, not a
> Users. It seems trivial, but it will help you in thinking in objects
> (entities) instead of tables.
> >
> > Second: what is your Relation-object? Do you need it? What is it that
> you try to model? Easier is not to start with the tables, but first have a
> look at what your "domain" is that you want to model. See next point too.
> >
> > Third: I doubt if a Relative is something else than a User. Probably
> relatives are other users. In that case it is a User entity with a
> ManyToMany association to itself: a User can have many other users as
> relatives and a User can be the relative of many other users. I always
> start with sentences like that.
>
>
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