A generic fill-in test plugin could be used for all kinds of grammar exercises. To my mind come:

- arrange words to form a correct sentence
- insert proper particles
- ...

The interface for this plugin would consist of two areas: at the top, there would be a text with gaps (or just gaps). At the bottom, there would be a list of words or phrases. The user should be able to drag and drop a word into any gap, replacing the word previously dropped there, if required.

Depending on the exercise, there could be more words than gaps, allowing false entries or multiple solutions.

The exercise data needs to provide a text with gaps to display (the task). A gap could be represented as a single underscore ('_'). It further has to provide the solution, possibly with different alternatives. And it needs to provide a list of words that go into the gaps, maybe with alternatives as well. Latter should be presented in random order to the user. I don't think a hint will be neccessary for this type of exercise.

The exercise data could therefore look as follows:

<?xml version="1.0"?>
<fill-in>
  <entry id="1">
    <task>Sangmin ! Na shinae _ kayo.</task>
    <solution>ssi do e</solution>
    <word>ssi</word>
    <word>do</word>
    <word>e</word>
    <word>i</word>
  </entry>
</fill-in>

(No utf-8 support here, so the example above uses the romanized form instead of proper Korean writing, as it is supposed to)

Note that the solution is a simple, space seperated list of the gaps filled in right order. That means, to verify the solution, all that needs to be done is concatenating what the user dropped into the gaps and comparing it to the solution string with help of TYK's diff class.

Gaps that were filled correctly should be kept, while wrongly filled gaps would be emptied to let the user retry.