SYSML — Section: Blocks - Definition of part properties

Definition of part properties. In Blocks, BlockProperty, 8.3.2.2, Description, second paragraph, it says: "A property of a block may refer to another element of a system that is required to exist for the system to exist. Such properties are called part properties." This means the minimum multiplicity of the property is always greater than zero. I assume part properties can be optional, ie, not required to have a value. Was this sentence meant to say that part properties are strong compositional? That would be consistent with UML's definition of the term "part property". If so, the spec should read: "A property of a block may refer to another element of a system, and when instances of the block are destroyed, instances of the other element will be destroyed. Such properties are called part properties." Same comment on another sentence in the same paragraph: "While referenced by the part property, however, these instances cannot cease to exist unless the owning system also ceases to exist." This isn't UML destruction semantics (see above) or consistent with a multiplicity of 0..1, as indicated in the paragraph. Is this intended?

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