# Formal¶

Directed
no
Source end
Multiplicity
0 - *
Target end
Multiplicity
0 - *
Binary properties

## Definition¶

The name «Formal» is short for Domain Comparative Formal Relation. This construct is used to represent relations that can be reduced to the comparison of the quality values that characterize the related individuals, like heavier-then, younger-then or cheaper-then. Here are some examples in OntoUML:

To specify how the relation can be reduced, use an OCL derivation rule:

context Person::lighter : Set(Person)
derive : Person.allInstances()->select(x | self.weight > x.weight)


Tip: Due to its ontological, the «Formal» relations have no constraints in OntoUML. Nonetheless, make sure the relation you are modeling is indeed a comparative one. Think about how to reduce the relation to a comparison between values and represent the necessary properties.

## Common questions¶

Ask us some question if something is not clear …

## Examples¶

EX1: Fragment from OntoEmerge, an ontology about Emergency Plans (see more):