Insomecases, relationshipsandevenroles canalsohave subgraphs.
There is also a wide variety of semantics associated with the subgraph links: Iivari
(1992) ?¬?nds ?¬?ve Boolean dimensions, for example whether the subgraph is owned
exclusively by one object, or several objects can all have the same shared subgraph.
The possible uses of subgraphs seem to vary along a scale of howformal the link is.
At the stricter end of the scale an object may only have one subgraph, and that link is
the same wherever the object is reused. At the freer end of the scale the link is more
like a note or hyperlink: an object may link to several different graphs, and that set of
graphs may be different when the object is reused elsewhere.
Explicit Concept of Port Modeling languages for describing hardware often
mimic electronic circuit diagrams in allowing an object to have a set of ports that
connections must attach to. These ports may have different semantics and rules, for
example, a ???power in??? port on one object must be connected to a ???power out??? port on
another object.Aport is thus a feature of an object type in a metamodel, and for ease of
use it is generally associated with a particular visible node on the perimeter of the
object symbol. Ports lend themselves to rules that are expressed over the whole
modeling language: ???in??? ports must always connect to ???out??? ports; a ???5 V??? port cannot
connect to a ???110 V??? port.
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