Third Party Product Integration: Relations

Prerequisites

To enable Relations install the Product ("code-location":http://plone.org/products/relations/).

Basics

As an option on command line, up to a tagged-value on model-level or on a single UML-Association you just define the
'relation_implementation' and set it to 'relations'. A directed Assoziation results in one Relation.

**Give the association and its assoziation ends names.** They'll be used as the names for the RelationField. If you dont want a field turn it off by setting a tagged value 'generate_reference_fields' on class (or package, model) level to '0'.

Inverse Relation

If the association is not directed (navigable on both association ends) an inverse relation will be created.

The tagged-value 'inverse_relation_name' will be used for the back-relation on undirected associations. It defaults to a relation named 'toend_fromend', where these are the lowercased versions of the association ends. If the two ends are named the same, then the relation will be named 'association_inv', where 'association' is the name of the association. (Finally, if the option 'old_inverse_relation_name' is set, then it defaults to the association name postfixed by '_inverse'.)

Cardinality

You can use the Multiplicity on in UML to define the cardinality of an Relation.
You can use the minimum and maximun value here using the syntax '1..5' which means at least one relationrelated objects but not more than five.

Constraints

type-constraint -- as described above an association between two portal-types will be created.

interface-constraint -- an association between an archetypes class and an interface will create an interface-constraint. the relation is allowed to all classes implementing this interface.

Association classes

Association classes can be used to store data on the relation as an object. You can model it using the UML association class or using a tagged value 'association_class' on the association.