[Rd] Formulas in gam function of mgcv package

[Corrado]

Dear R-experts,

I have a question on the formulas used in the gam function of the mgcv 
package.

I am trying to understand the relationships between:

y~s(x1)+s(x2)+s(x3)+s(x4)

and 

y~s(x1,x2,x3,x4)

Does the latter contain the former? what about the smoothers of all 
interaction terms? 

I have (tried to) read the manual pages of gam, formula.gam, smooth.terms, 
linear.functional.terms but could not understand properly.

Regards
-- 
Corrado Topi

Global Climate Change & Biodiversity Indicators
Area 18,Department of Biology
University of York, York, YO10 5YW, UK
Phone: + 44 (0) 1904 328645, E-mail: ct529 at york.ac.uk