categorization scheme for dublin_core Subject

Hello

I tried to find in the Web the Dewey Decimal Code for library science .
This is just one possible categorization scheme for Dublin Core Subject
property. What about other Web-accessible categorization schemes?

Thanks

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<person>
  <first_name>Jean-Marc</first_name>
  <name>Vanel</name>
  <project>Worlwide Botanical Database - making available botanical data
on Internet
    <a href="http://jmvanel.free.fr/" >site</a>
  </project>
  <a href="mailto:jmvanel@free.fr">mail</a>
</person>