Relations with Alex Mitchell


This tool lets you establish relationships between any two object types in Zope. The problem is that it is functionally duplicating with Zope/ZODB what relational databases give for free. (Danny 07/05/2011)

What is zc.relationship?

  • A low level ZODB index for querying relationships
  • Highly optimized for simple relationships across large data
  • Default confi allows relations between arbitrary persisten objects
  • index can be confired to index complex relationships including non-ZODB objects
  • provides transitive searches
  • con: hard to use in Plone

What is Plone.relations?

  • A local utility built on zc.relationship, which is application to a wide variety of relationship models
  • A relationship class that models many-to-many contentl relationships
  • Some options aspects of the relationship are also indexable

What is

  • higher level API
  • Content object for UML
  • A set of optional adapters and subscribers
  • DC workflow for relationships
  • “Holding” relationships
  • Relationships which are copied when their source is copied.
  • example Plone code:
src = IRelationshipSource(obj)

Relationship Source

  • IrelationshipSource

    • Create (createRelationship), supports multiple targets
    • Query (getTargets, isLInked, getRelationshipChains, getRelationships)
    • Modify (deleteRelationships)

Relationship Targets

  • IRelationshipTarget

    • Same query methods and parameters as IRelationshipSource + getSources
    • ISymmetricRelation

    -Query (isLinked, getRelationships, getRelations)

Code Samples

stuff from the presentation:

>>> class IFriendship(IDCWorkflowableWorkship):
      """A friendship"""
>>> source = IRelationshipSource(obj)
>>> rel = source.createRelationships(obj, relation='friend', interfaces=(IFriendship)
>>> list(source.getRelationships(relation='friend')
<lazy list response>
>>> list(rel.targets), list(rel.sources)
>>> list(source.getTargets())
>>> target.isLinked()

What can you do with it?

  • Model non-container relationships you might need
    • Social networking
    • User favorites
    • Placeless content
    • taxonomies or complex vocabularies

What has been done with it