skos:prefLabel without language tag

Dear all

The SKOS specification about language tags has only the restriction.
"A resource has no more than one value of skos:prefLabel per language tag"
It does says otherwise that the language tag is optional for labels, but all
ex

-- 
Bernard Vatant
Senior Consultant
Vocabulary & Data Integration
Tel:       +33 (0) 971 488 459
Mail:     bernard.vatant@mondeca.com
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