Recently the new SKOS Reference (2009) was released after two rounds of world-wide comments.  However, most of the questions related to the specific issues of classification systems raised by the authors resulted in no change to the SKOS specification. Realizing the differences between the underlying models of what SKOS and OWL (Web Ontology Language)  intended to support, the authors has been studying OWL 2 (2009) to explore issues and opportunities.  This paper will summarize a number of situations found in three general enumerative or partly enumerative classifications.  The authors bring together evidence of using OWL to resolve major issues related to classification systems and discuss the differences of SKOS and OWL that mainly support two different kinds of models underlying thesauri and classification systems.