Accessing local files to launch helper progam using \useURL and \from

[Matthias Weber <matweber@indiana.edu>]

Dear all,

I am trying to us \useURL and \from with mixed success to access a  
local file so that it will be
opened by a helper program. Both the program and the file to be  
opened by it
reside in my local file system. Here is a small example:

\setupcolors[state=start]

\setupinteraction
[state=start,color=blue]


\useURL[cycloids][{file://3dxm/cycloids.stng}][][3DXM]

\starttext

\inmargin{\from[cycloids]}
In this section, we study curves that are obtained by tracing a point  
on a fixed circle while it is rolling  along another circle.

\stoptext



cycloids.stng is a file, that, when double-clicked, starts a program  
it is associated with.
For trying, you can replace it by any other file that uses a special  
application to go with.

Unfortunately, this *only* works with the pdf viewer in TeXShop (I am  
on a Mac).
Preview doesn't do anything but beep, and Acrobat 6 offers a few  
choices, none of which is to
open a helper application. Does anybody know if there is another way  
of launching helper
applications when accessing documents?

Also, while at it: When accessing local files, the URL appears to be  
absolute. Is there a way to use
URLs relative to the location of the PDF that is referencing the URL?

Thanks,

Matthias