The spec is very clear, <foreignObject> can be used inside other elements than <switch>

Each element definition said specifically if it can contain <foreignObject> or not.
for example, see : http://www.w3.org/TR/SVG/struct.html#SVGElement

So it seams that the RelaxNG file is flowed :-/

All the following elements can contain <foreignObject> (according to SVG 1.1 2nd Edition)

svg
g
defs
desc
title
symbol
switch
style
marker
mask
a
script
glyph
missing-glyph
metadata

This changed in SVG 1.1 Second Edition...

http://www.w3.org/TR/2010/WD-SVG11-20100622/changes.html#WholeDocument

There is also no official RelaxNG supplied by the Working Group for SVG 1.1 Second Edition.  Sounds like this is just a bug that needs fixing in the validator.

(In reply to comment #3)
> There is also no official RelaxNG supplied by the Working Group for SVG 1.1
> Second Edition.

The validator.nu backend uses the schema from http://www.w3.org/Graphics/SVG/1.1/rng/

> Sounds like this is just a bug that needs fixing in the validator.

The "bug" is that the validator.nu backend is using a schema that apparently has not yet been updated to incorporate the changes made for the second edition of SVG 1.1. That's kind of expected since validator.nu has had SVG 1.1 support for several years now, and SVG 1.1 second edition only became a Rec two months ago... 

If the SVG WG is not officially maintaining the http://www.w3.org/Graphics/SVG/1.1/rng/ schema, then I'd suggest the group consider doing that, and updating it with the changes for the second edition.

It would seem very odd to me for the group to provide an updated DTD but not an updated RelaxNG schema.

(In reply to comment #2 from Robert Longson)
> This changed in SVG 1.1 Second Edition...
> 
> http://www.w3.org/TR/2010/WD-SVG11-20100622/changes.html#WholeDocument

Thanks -- I was confused about where the discrepancy came from. Now it's clear.