For clarity, a Notice is eg a Wedding, Birth or Death announcement which appears in a newspaper. This is (an excerpt of) what my DB looks like:

   Table: object (generic object)
   ------------------------------
    id
    type_id
    status
    parent_id
    creator_id
    created
    last_modified

  Table: notice (adds notice specific fields to the object table)
  ---------------------------------------------------------------
    id (1 to 1 relationship with object.id)
    notice_type (ie wedding, funeral, birth etc)
    title
    content
    etc

  Table: charity (adds charity specific fields to the object table)
  -----------------------------------------------------------------
    id (1 to 1 relationship with object.id)
    name
    description
    url
    etc
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The editor of a notice can choose a number of charities to link to, so a notice can have many charities. This is stored in the members table:

   Table: members  (link table)
   ----------------------------
    set_id    (in this example, the notice ID)
    member_id (in this example, the charity ID)
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Notices can have many Comments, Images, Charities, Editors. So my question really boiled down to, should I have

• separate List/Set/Container objects for each list of items, so that you create a new ImageList, which is a child (not a subclass) of the Notice, and the members.set_id == ImageList.id
• or set_id == notice.id, and then you filter the set members you want by object type (ie image/comment etc)

After discussion in the CB with bart and castaway, I think i've abandoned both of those, and now what I'm going to do is the following:

• A Set does not live in the database as an object, neither does Notice inherit from the Set
• Instead, I can create a Set object as follows:

     $set = Set->new({
          set_id      => $notice->id,
          name        => 'imagelist',  # combined with set_id to provide
  + an ID for caching
          selectors   => {
              type       => 'image'
          },
     });
  [download]

  ... which is really just a glorified array, with methods to check membership, and to add / delete members from the list, almost like an SQL view.

Technically your 1:1 are really 1 to many because 1:(0or1) is implemented in practice as a 1 to many inthat order. The set/notice is in theory a many-to-many which is more normally implemented as member -< member-notice >- notice with member-notice as the link table, so that the "set" is really a view on member-notice for a given notice.

What I'd be doing about sets is making a container object "set" that requires an instance variable to have a particular notice filled in so it can go retrieve all member-notice pairs for that notice, thereby populating the container class.

__________________________________________________________________________________

^M Free your mind!

I understand your second para, and yes, that is what I'm doing.

But would you mind explaining your first para? Why is the 1:1 actually 1 to many? Are you refering to the Object/Notice join, or to the Members table? I realise it is a many-to-many relationship, with a link table giving you many-to-one and one-to-many for notice and charity respectively. Is that what you're talking about?

I'm not familiar with the terminology, which is probably why I'm missing something here (eg 1::Oor1).

thanks moron

clint