Define functions in R in uninstalled packages?

I know that there are several ways to define the functions in a given package in R if the package is already installed. For example, to search for functions associated with the XML package, you can use any of the following functions:

lsf.str("package:XML")

help(package="XML")

ls(pos = "package:XML")

But I want to find all the functions for a package that are listed in a format similar to how one of these 3 methods represents them in R, without actually installing the package. I know that the PDF manual for this package contains a list of functions; but I need something more dynamic (for example, which can be accessed in R or on a web page, for example). And I do not find anything like it on the CRAN website. Here is an XML site, for example: http://cran.r-project.org/web/packages/XML/index.html

And ideally, I need this to summarize any / all (or at least most) of the 5,000 + existing R. packages.

Is it possible?