Things exist (citation needed).

Things are either entities (’objects’) or behaviors (’processes’). Things can relate to one another. Things can relate to one-another in infinitely many ways. However there are multiple takes on categorizing and enumerating the ways in which things can relate to one-another, particularly in the realm of MBSE. Here are some categories that have been used in SysML, OPM, and IDEF to bucket the way things can relate.

Note: OPM contains a graphical representation “OPD”, and a textual one “OPL”

Relationship Categories

Composition: A —composed of→ B

An object is made up of smaller objects. Or a a process is made up of smaller processes.

In	Validity	Related Properties
SysML
OPM
IDEF	Object-to-Object
Process-to-Process	Source & Destination Multiplicity

Representation:

OPD/OPL

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SysML

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IDEF

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Exhibition: A —exhibits property→ B

An object has an attribute. A process has an attribute.

In	Validity	Related Properties
SysML
OPM	Any-to-Any	Unit

Representation:

OPD/OPL

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SysML

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No graphical notation, instead properties are included

Generalization: A —is a→ B

An thing is a more specific version of another thing.

In	Validity	Related Properties
SysML
OPM
IDEF	Object-to-Object
Process-to-Process

Representation:

OPD/OPL

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SysML

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IDEF

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