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Unique ID implementation for Zope Content Mangement Framework (CMF) content
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CMFUid introduces a simple unique id implementation.


The supplied tools attach the unique ids to the objects. The objects do not have to be aware of unique ids.

The current implementation depends on the portal catalog to find an object of a given unique id. The interfaces do not imply the use of the catalog (except the IUniqueIdBrainQuery).

Which Tool does What?

The 'portal_uidgenerator' tools responsibility is to generate unique ids. The 'portal_uidannotation' tool is responsible to attach unique ids to a content object, and enforce rules about what happens on object move/create/delete. The 'portal_uidhandler' manages registering and accessing unique ids.

This design was chosen to allow users replacing only parts of the functionality without having to understand the whole thing.

Unique Id API

'portal_uidhandler' implementing 'IUniqueIdHandler' is the main API for playing with unique ids.


'portal_uidhandler' fully implements IUniqueIdHandler (IUniqueIdSet for registering/unregistering unique ids, IUniqueIdQuery for queries and IUniqueIdBrainQuery for more efficient queries by returning catalog brains instead of objects).

The current implementation of get/queryBrain and get/queryObject do not return invisible objects (and brains of invisible objects). By invisible objects, we mean objects that would be filtered out by portal_catalog.searchResults due to expiry/effective date and/or user roles.

It is often necessary to avoid this filtering in an application. To do this, use the unrestrictedGet/QueryBrain and unrestrictedGet/QueryObject as this will avoid 'None' results.

Have a look at the interfaces.

CMFUid's functionality is used by CMFDefault's favorite content type to follow linked objects. The favorite content type works as before if CMFUid is not installed.

Update 2007-03-30

The annotation code has been updated to use events for assigning/removing uids. The settings for this live in the portal_uidannotation tool.

The default behaviour is:

  • uids are NOT assigned when an object is created (it is assumed that other code is responsible for this)
  • when an object is moved, a UID is not changed
  • when an object is imported, any EXISTING UID is removed (this can be controlled via the 'remove_on_add' property)
  • when an object is copied, any EXISTING UID is removed (this can be controlled via the 'remove_on_clone' property)

A more natural behaviour is for UIDs to be assigned automatically on creation. To enable this feature:

  • tick the 'assign UIDs on add' tickbox (uids will now be assigned when content is added or imported and any EXISTING uid will be replaced)
  • tick the 'assign UIDs on copy' tickbox (objects will get a NEW uid when they are copied which will replace any EXISTING uid)

In order to preserve the original behaviour of the tool, automatic assignment of uids is NOT enabled by default - it must be turned on in the uidannotation tool.

The behaviour is hooked in based on object creating/deletion/move events for any IContentish objects. The event handlers live in the UniqueIdAnnotation tool.

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