CCK reference filter enhances the user experience and ensures data integrity in a number of common use-cases involving node references:
o from an originating node to a destination node
o from an originating node to a destination user

What does it do?

When using a CCK reference field to link the originating node to one or more other nodes or users, this package will restrict the nodes or users available for selection to those that have not yet been referenced from any other origination node.

When would I use it?

Here are some typical scenarios of users and nodes that must be referenced from no more than one originating node.

• a CMS containing a directory of companies and organisations, each referencing a contact person who is a registered/authenticated user on the site; each user may be a contact for one company or organisation only
• a site featuring nodes of type meeting, each of which reference one agenda node and one meeting-minutes node; both agenda and minutes belong to that one meeting only
• a repository of financial reports whereby each company's financial annual report (node) references up to 12 monthly report nodes belonging to that company only
• a site with teams of some kind whereby the members/players have logins on the site; each player can be in one team only

In general: any one-to-one or one-to-many parent-child relationship whereby a parent may have multiple children, but each child belongs to only one parent. In other words: child selection is mutual exclusive.

Put another way, this package makes sure that the UI offers only 'orphan' nodes and users as valid destination references.

The CCK reference filter project page contains all installation instructions, as well as answers to some frequenctly asked questions.