A synonym for LiskovSubstitutionPrinciple, but with a wider application. It applies not only to objects and classes, but to all entities that may be substituted for each other.

This includes:
	- Use Cases ("Buy Gas With Credit Card" <is a> "Buy Gas")
	- Relationships (Composition <is a> Aggregation <is a> Association)
	- Others 

-- DanRawsthorne
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Programmers, for example ;-)