DocBook Publishers Schema

Hi folks

I've just come back to DocBook after about a year away and I'm doing some work that's going to involve using the Publishers Schema. I've come across an inconsistency that I'm unsure about. 

The spec for the schema lists <toc> as an included element. However, publishers.rnc does not include toc.rnc either directly or indirectly as far as I can tell. Have I missed something or not? 

cheers

nic
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Nic Gibson
Director, Corbas Consulting Ltd
Editorial and Technical Consultancy and Training
http://www.corbas.co.uk, +44 (0)7718 906817