To: gopher@complete.org
Subject: [gopher] Links to URL
References: <200202120132.RAA11190@stockholm.ptloma.edu>
From: John Goerzen <jgoerzen@complete.org>
Date: 12 Feb 2002 14:19:46 -0500
In-Reply-To: <200202120132.RAA11190@stockholm.ptloma.edu>
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I think it is best to start small with modifications to the protocol.
Therefore, I propose the following:

Method to link to URLs from Gopherspace
---------------------------------------

1. Protocol issues

Links to URLs from a gopher directory shall be defined as follows:

 Type -- the appropriate character corresponding to the type of the
 document on the remote end; h if HTML.

 Path -- the full URL, preceeded by "URL:".  For instance:
         URL:http://www.complete.org/

 Host, Port -- pointing back to the gopher server that provided
 the directory for compatibility reasons.

 Name -- as usual for a Gopher directory entry.

2. Conforming client requirements

A client adhering to this specification will, when it sees a Gopher
selector with a path starting with URL:, interpret the path as a URL.
It will ignore the host and port components of the Gopher selector,
using those components from the URL instead (if applicable).

3. Conforming server requirements

A server with Gopher URL support will not, in most cases, need to take
extra steps to provide this support beyond those outlined in
Compatibility below.  Servers not implementing those steps outlined in
Compatibility will be deemed to be not in compliance.

4. Authoring compliance

The use of URL: selectors should be avoided wherever possible.  In
particular, it should be avoided when pre-existing gopher facilities
exist for the type of content linked.  The following URL types are
explicitly prohibited by this specification:

  gopher
  telnet
  tn3270

Authors should avoid links to any document not of HTML type whenever
possible.  Linking to non-HTML documents will break compatibility with
Gopher browsers that do not implement this specification.  The ranks
of these browsers include most Web browsers, so that is a significant
audience.

5. Compatibility

Links to HTML pages may be accomodated even for non-comforming
browsers by providing additional capabilities in the server.

When a non-conforming browser is instructed to follow a link to a URL,
it will contact the Gopher server that provided the menu (since these
are specified per section 1).

When a conforming Gopher server receives a request whose path begins
with URL:, it will write out a HTML document that will send the
non-compliant browser to the appropriate place.  One such conforming
document is:

  <HTML>
  <HEAD>
  <META HTTP-EQUIV="refresh" content="2;URL=http://www.acm.org/classics/">
  </HEAD>
  <BODY>
  You are following a link from gopher to a web site.  You will be
  automatically taken to the web site shortly.  If you do not get sent
  there, please click
  <A HREF="http://www.acm.org/classics/">here</A> to go to the web site.
  <P>
  The URL linked is:
  <P>
  <A HREF="http://www.acm.org/classics/">http://www.acm.org/classics/</A>
  <P>
  Thanks for using gopher!
  </BODY>
  </HTML>

This document may be any desired by the server authors, but must
adhere to these requirements:
 * It must provide a refresh of a duration of 10 seconds or less
 * It must not use IMG tags, frames, or have any reference whatsoever
   to content outside that particular file -- other than the link
   to the real destination.
 * It must not use JavaScript.
 * It must adhere to the W3C HTML 3.2 standard.

When a non-conforming Gopher client finds a reference to a HTML file
(type h), it will open up the file via Gopher (getting the redirect
document) but using a web browser.  The web browser will then be
redirected to the actual link destination.  Conforming clients will
follow the link directly.

END


Comments?