How to link to a fragment (aka anchor/bookmark) of a local file (e.g. a TiddlyWiki)?

[Christoph LANGE <ch.lange@jacobs-university.de>]

Dear all,

I know that org-mode supports links to local files via relative file:
URLs, e.g. file:filename.html.  It also supports links to fragments (aka
anchors/bookmarks) in remote files via http: URLs, e.g.
http://www.example.org/filename.html#section2.

Now, is there a way to combine these?  I would like to use something
like file:filename.html#section2 to link to a fragment in a file that is
in the same directory as my org file.  For portability reasons I don't
want to use any other way of linking to that file than a relative file: URL.

Please read on if and only if you are interested in my reasons for
wishing for such a feature :-)

My concrete use case is that before learning about org-mode I managed my
personal knowledge in a TiddlyWiki (http://www.tiddlywiki.com/), and
some of my knowledge I'm still keeping there.  (Why?  See below.)  The
pages ("tiddlers") in a TiddlyWiki can be accessed as fragments of the
TiddlyWiki HTML file, e.g. file:/path/to/tiddly.html#WikiPage.  I have
my TiddlyWiki file in the same directory as my org file and would like
to link to specific pages of it using file:tiddly.html#WikiPage in order
to achieve a tight integration between both knowledge collections.

FYI, and really just FYI, as I don't want to start a flamewar: The one
single thing that I still like better in TiddlyWiki than in org-mode and
that I haven't been able to reproduce in org-mode is that I can organize
my knowledge in a hierarchical and linked way by tagging pages with
other pages.  E.g. I could have a page OrgMode tagged with
ProductivityTool, where ProductivityTool would not merely be a tag, but
the name of another page, which contains general information about such
tools.  That is, to the best of my knowledge, not possible in org-mode,
which treats outline headlines and tags as two completely different things.

Cheers, and thanks in advance for any help,

Christoph

-- 
Christoph Lange, http://www.facebook.com/ch.lange, Skype duke4701