How Can I Lock Cells to Keep Them From Prying Eyes?

[Gregory]

Hello everyone,

Well, I guess the subject header to this post says it all. I'm trying to develop a workflow for a large number of assignments for various courses in financial economic theory. I want an exercise cell or cells followed immediately by an answer cell or cells. When the assignment is distributed, I want the answer cells closed and locked; after it has been graded, I want to redistribute the same document with the answer cells now open. The documents will be distributed as CDF and PDF, but students do have access to the full version of Mathematica, so I need to make sure that they cannot use the full version to open locked cells. Any way to do this?

The alternative would be to have duplicate documents: one with only exercises and the other with exercises and answers. It's doable but pain.

Regards,

Gregory

[Michael_Morrison]

Hi, Gregory,

I don't know of a foolproof way to do this. For example, when I develop materials, I sometimes create cells with certain tags so that I can use front end commands like NotebookLocate to select the tagged cells and then hide them by setting things like CellOpen->False and Selectable->False, and then I can use the same commands to find them and change those settings so that they reappear. I do this so often, in fact, that I have a pair of buttons that I use over and over to toggle those cells between hidden and shown, depending on what I'm doing. This is easily reversible by a recipient of the file, however, if the recipient knows how to use the Cell Tags menu item in the front end, or if they just do a Select All and then then play with toggling Cell Properties > Open. If this is not a concern, then using an approach like this might be good enough.

You can take things a step further and set the entire notebook as Selectable->False (this disallows the Select All/Cell Properties->Open trick), but this is still able to be undone by someone who knows his or her way around the Option Inspector.

If you want to be absolutely sure that the content for your answer cells is not viewable until you want it to be, then I think your best option is to keep two separate sets of files: one with answer content, and one without. This doesn't need to be as tedious as you might think, however. You could set up a stylesheet so that you use a specific style for answer cells. Then, you author the master copy (with questions and answers included) of your document. Finally, when you want to create the version without answers, you can Alt+click (or Option+click on Mac OS) the cell bracket of a single answer cell, and Mathematica will select all cells of that same style in your notebook. Then you can hit the Delete key once, Save As with a new filename, and you're done.

You could do a similar approach by using cell tags (instead of a special cell style) for the answer cells, use NotebookLocate to select all of those cells, and then hit the Delete key to wipe out all the answers at once. I might lean towards this method because you could write a single command that would select the answer cells, delete them, and open the File > Save As dialog screen for you to save the "distribution" version of your document with a new filename. Yes, it's an extra step, but it helps minimize the effort required to create two different versions of each document.

If you'd like to see an example of any of these ideas, I'm happy to put something together for you.

Regards,
Michael

[bsyehuda]

Unfortunately I have to support Michael's answer which is complete (to my best knowledge). The options are interpreted by the front end, and as such, are controlled by it.
One comment though. If the course material is not about Mathematica programming, I assume that the "secrete" (and maybe "secret") knowledge of cell options is not easily revealed (if one allows to be fully optimistic).

yehuda

[Tom_DeVries]

Hi, I teach for an online school and I am doing pretty much exactly what you are doing. Students use CDFPlayer to view the files I create.

I use the method given above. I tag all "answer" cells with the cell tag answer (seemed logical!).

I create a test by pulling questions in from various question banks, save the file with a name that has "q" in it, then use NotebookLocate to locate the answer cells, delete them, and resave with a name that has "a" in it. It works quickly and easily and at present, I think is the only way to be sure students can't get at the content.

TOM

[Gregory]

Hi Tom,

Thanks for the tip. Seems like a good approach.

Gregory

Hi, I teach for an online school and I am doing pretty much exactly what you are doing. Students use CDFPlayer to view the files I create.

I use the method given above. I tag all "answer" cells with the cell tag answer (seemed logical!).

I create a test by pulling questions in from various question banks, save the file with a name that has "q" in it, then use NotebookLocate to locate the answer cells, delete them, and resave with a name that has "a" in it. It works quickly and easily and at present, I think is the only way to be sure students can't get at the content.

TOM