Using Caché Objects - InterSystems Documentation

Relationships
14.1 Relationship Basics
The fundamental aspects of using relationships are relationship keywords and the action of
defining a relationship.
14.1.1 Relationship Keywords
There are three keywords or modifiers required to define a relationship property:
TYPE
The type (class name) of the related class. This must be a persistent class.
INVERSE
CARDINALITY
The name of the corresponding relationship property in the related class (the “other
side” of the relationship).
The cardinality of this side of the relationship. This is either “ONE” , “MANY” ,
“PARENT” , or “CHILDREN” — where the class' inverse has the complementary
cardinality, such as MANY with ONE or PARENT with CHILDREN
Because each relationship is defined using a relationship property, which is a particular kind
of property, some other property keywords are available for use in them, including
“DESCRIPTION” , “FINAL” , “REQUIRED” , “SQLFIELDNAME” and “PRIVATE” .
Some property keywords, such as “MULTIDIMENSIONAL” , do not apply. See the Property
Keywords section of the Class Definition Reference for more information.
14.1.1.1 About Cardinality
The value of “CARDINALITY” defines how the relationship “appears” from this side as
well as whether it is an independent relationship (ONE-MANY) or dependent relationship
(PARENT-CHILDREN).
For example, suppose we have a Book object that is related to MANY Chapter objects:
The relationship Book.Chapters has cardinality of MANY. Each Chapter is related to ONE
Book so the Chapter.Book relationship has cardinality of ONE.
In the case of a dependent relationship, such as an Invoice object with dependent LineItem
objects,
126 Using Caché Objects