2.5.5 Relationship

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2.5.5 Relationship

The <relationship> element is a child of the <entity> element. It has the following attributes:

<relation 
    name                   = ''   -- relation name
    deleteRule = ( 0,DELETE_NULLIFY | 1,DELETE_DENY | 2,DELETE_CASCADE |
                   3,DELETE_NOACTION ) : 0  -- behaviour when object is deleted 
    isClassProperty        = '1'  -- '0' or '1'; relation is also a class property
    multiplicityLowerBound = ( int > -1 ) : 0
    multiplicityUpperBound = ( int > -1 | -1,* ) : 1
                                  -- -1 or * indicate unconstrained upper bound 
    destinationEntity      = ''   -- name of destination entity
    joinSemantic = ( 0,Inner | 1,FullOuter | 2,LeftOuter | 3,Right Outer ) : 0
    displayLabel            = ''  -- text label to use in applications
    comment                 = ''  -- a comment
>
</relation>

All these attributes are described in section 2.3.4.

Here are the possible values for these attributes, and their meaning:

isClassProperty:

code'0': DELETE NULLIFY
'1': DELETE DENY
'2': DELETE CASCADE
'3': DELETE NOACTION

Note: in future it will be possible to enter the real names (such as DELETE_CASCADE), not only their numerical value (defined in module ClassDescription.

isClassProperty:

Default value: '1' (Yes). '0' stands for No.

multiplicityLowerBound, multiplicityUpperBound:

You can enter '*' or '-1' for an unconstrained upper bound.

Default values: '0' for lower bound, '1' for upper bound.

joinSemantic:

Possible values and their respective meaning are:

'0': (default) Inner join
'1': Full outer join
'2': Left outer join
'3': Right outer join

(as defined in module Relationship)

The full definition of a relationship implies that it defines at least one join.