Show specific page in yelp

Hi everbody!

I like to define which of all pages is being displayed when my docbook
is opened by Yelp. The docbook will be opened from within applications.
The shown page should match the context of the program. Also the docbook
can be opened without a context. Then my favourite page shall be
displayed.
How do I specify a default page for Yelp? How do I make Yelp display a
specific page?

Thanks a lot,

Timo