[Seaside] How to access parameters in url

[Kai-Uwe Pielka]

Hello,

I moved from 2.8.4 to 3.0a
With 2.8 parameters in the URL could be accesses with 'session  
fieldsAt: 'parameterName'.
How does this work in 3.0a ?

Thanks in advance,
Kai-Uwe