Excercises, randomly generated and automatically checked

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I've been authoring excercise questions for students using Maple T.A.. These questions are randomly generated, and answers checked online, which gives immediate feedback to students. Students like this service, but I as an author was severely annoyed by the workflow, and thought that it should be possible to achieve something better using Sage.

Is there any project underway which attempts to use Sage to generate questions and check answers in a web-based setup? If so, how mature is it?

If you want an example question, I'd be particularly interested in a question asking students to find an orthogonal basis for a vector space spanned by a given set of vectors. As that basis isn't uniquely defined, a fixed answer won't work, so the provided answer has to be checked using custom code. As the dimension of that vector space might vary between randomizations, a fixed input form doesn't seem a good idea, so I'd prefer either some JavaScript tool to manually adjust the number of vectors in the HTML page, or some way to enter a set of vectors as a single expression. The latter is the approach I currently take with Maple T.A., but it requires students to not only worry about their computations but also about the syntax for entering the results. And it raises the question of how to restrict the set of possible inputs, as executing arbitrary user-entered Python code would be a road to disaster, unless some reasonable sandbox were available.