Association

Associations are structural relations between classes. Netsilon handles only binary associations but supports class-associations. An association links classes through its endpoints. An association or an endpoint may or may not be named. An endpoint must be named to remove an ambiguity in a Xion expression.

Properties

Name	Name of the association. Can be omitted.
Role name - endpoint	Name of the role – endpoint. Can be omitted unless there is an ambiguity, for example, two or more associations between the same classes whose endpoints are not named. Xion: if omitted, the name of the role is the name of the class linked to the endpoint with the first letter set to lower case. If the name of the class is not capitalized, the endpoint is not visible in Xion.
Multiplicity - endpoint	The number of instances of the class on this side of the association that can be linked to an instance of the class on the other side of the association. 1: after creation, one object should always be linked to the other object 0..1: an object is or is not linked to the other one 1..*: at least one object is linked to the other one 0..*: no restriction on the number of objects linked to the other one
Aggregation - endpoint	An aggregation is a nonsymmetrical association in which an endpoint plays a dominating role compared to the other. An aggregation relates to only one role of an association. none: symmetrical association aggregation: nonsymmetrical association – no special treatment in Netsilon composition: nonsymmetrical association – in Netsilon, objects linked to an other one by a composition are deleted automatically when the latter is deleted
Navigable - endpoint	It indicates whether an association is navigable from the other object to this one
Classifier - endpoint	The classifier associated to this endpoint
Stereotype	Ignored

Class-association

A class-association can be seen either as a class or as an association. A class-association presents hidden associations 0..1-0..1 towards the classes it links together. When an instance of a class-association is created, the links between the instance of the class-association and the two instances that should be linked together must be set to materialize the link. Since an association between classes is a set, a non initialized instance of a class-association (both references to the end classes set to null) will prevent any new creation of an other instance.