BASE interpretation

Rob Hartill (
Tue, 11 Oct 1994 21:35:20 +0100

Hi all,

How is BASE supposed to be interpreted ?

I like the way Xmosaic does it - by replacing the current URL
with that specified by the document. However, other people think
it should just provide a way to resolve relative URLs. One beta
client even allows multiple BASEs to be present in any part of the document.

The HTML 3 spec is ambiguous (to me anyhow), as to how BASE is to
be interpreted.

As a compromise, I'd suggest that if there's a BASE inside the <HEAD>,
then this should be treated as a replacement URL and relative URLs are
relative to it. The client will not attach its own BASE when exporting
the current document, if one exists inside <HEAD>.

If a BASE appears outside the <HEAD> then it doesn't replace the existing
URL, but does affect subsequent relative URLs.

There's an argument that allowing the displayed URL to change can
be used to trick the user into thinking (s)he's at some other site. -
a simple solutions is to display both the original URL and the new URL
if they have different host addresses.

I can provide examples of how useful the Xmosaic interpretation is
if required.


Robert Hartill            (
Los Alamos National Laboratory               T-8 office: (505) 667 5336
Theoretical Division, T-8, MS B285                  Fax: (505) 667 5585
P.O. Box 1663
Los Alamos, NM 87545, U.S.A.