sh:uniqueLang and empty lang tags

https://www.w3.org/TR/shacl/#UniqueLangConstraintComponent says
"for each *non-empty language tag *that is used by at least two value
nodes..."

Why is that? I think that either of these nodes should cause a validation
error:

:Person1 rdfs:label "Alice",    "Bob".
:Person2 rdfs:label "Alice"@en, "Bob"@en.

https://www.w3.org/TR/skos-reference/#S14  does not exclude empty tags from
validation, yet all examples it gives are of non-empty tags.
Yet the intent is clear: to be able to pick a single label based on some
lang preferences.
In the case of two plain strings, you can't pick one of them reliably.

Cheers!
-- 
Vladimir Alexiev, PhD, PMP
Chief Data Architect
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Received on Tuesday, 24 March 2020 08:56:48 UTC