Extending the Org syntax by a custom exporter - how to do it?

[Marcin Borkowski <mbork@wmi.amu.edu.pl>]

Hi list,

I'd like to extend the LaTeX exporter to be able to prepare tests with
Org-mode.  Four basic kinds of tests I'm thinking about are: single
choice test, multiple choice test, cloze test and an "open" question
(where the expected answer is, say, at most 5 lines of text).  It
would enable the user to typeset both the test for students and an
answer sheet for the teacher to facilitate grading. (If - and when - I
succeed in doing this, next logical step is preparing HTML/Javascript
tests from the same Org-mode source.)  I have a few questions, though.

1. Is it possible to employ syntax like ____{noon|midday} to denote a
cloze with two possible answers?  It might get translated to LaTeX as
e.g. \cloze{{noon},{midday}} or similar, and a LaTeX package would
take care to typeset this correctly.  Is there any similar thing (i.e.,
an exporter built on some existing one) so that I can look at an
example of code doing such thing?

2. What would you suggest as the input format on the Org side of
things?  My suggestion for the cloze syntax is shown above (let us
assume that at least two or three underscores are needed to
distinguish this from subscript, and some form of escaping the pipe
symbol and braces might be necessary.  Alternatively, it might be
configurable to use e.g. ____[noon/midday] (or other characters).

What about SCTs/MCTs?  My idea would be to employ plain lists with
checkboxes - they seem to be pretty useless outside Org-mode anyway,
and I imagine that it could be something like this:

#+<SOME MAGICAL LINE MEANING: THIS IS A MULTIPLE CHOICE TEST>
- [ ] wrong answer
- [X] good answer
- [X] another good answer
- [ ] a completely stupid answer

As for "open" questions, I have no good idea.  Maybe something like

#+LINES: 5

but what about example answers (for the teacher grading the test)?
Maybe it would be better to say:
#+BEGIN_ANSWER
(Here goes the right answer.)
#+END_ANSWER,

but is it possible to pass a parameter (number of lines) to
#+BEGIN_ANSWER?

3. Bonus question: would there be any demand (apart from myself) for
such an exporter?

What do you think?

-- 
Marcin Borkowski
http://octd.wmi.amu.edu.pl/en/Marcin_Borkowski
Adam Mickiewicz University