OWL and Vocabularies

Hello

I want to use the Dublin core vocabulary to describe classes within a schema. By importing the vocabulary into a schema am I saying that classes mentioned in the 
importing schema can be annotated using DC terms?
If importing is not the solution, do I need to declare each DC element within my ontology?
Currently, my data files (a-boxes) contain individuals from a schema 
(t-box). Some of the individuals contain DC properties that are not 
mentioned or imported in the schema. Is this bad practice?


Regards Rory.