Submitting problems to the OPL

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One of WeBWorK's most attractive features is the Open Problem Library, a collection of over 20,000 problem files contributed to the project by faculty from a wide variety academic institutions. The procedures outlined here are intended to encourage others to contribute problems to the OPL, but also to maintain high standards for the problems contributed.

Note the National Problem Library, or NPL, was renamed the Open Problem Library, or OPL in 2012.


Who can contribute to the OPL?

Anybody can contribute to the OPL. Typically, contributors are familiar with WeBWorK and have a reasonably good understanding of the PG language and the MathObjects framework.

If you have already written a collection of WeBWorK problems and want to share them with other WeBWorK users, we will gladly include the collection to the problems distributed with the Open Problem Library. A collection of problems can be submitted all at once, when the collection is complete, or the collection can be built over time in a dedicated subdirectory of the OPL. Initially, problems are put in the Contrib portion of the OPL. Selected problems may then be copied to the part of the OPL which gets indexed by the Library Browser.

Overview of contributing to the OPL

There are two parts of the OPL confusingly named "OpenProblemLibrary" and "Contrib". When users install the OPL, they get both parts. The differences are

  • problems in OpenProblemLibrary are tagged and indexed in a database on the webwork server so users can search for them with the Library Browser based on a three-tier taxonomy (Subject/Chapter/Section).
  • Contrib problems can be tagged, but they are not indexed. Individual sites can make them visible in the Library Browser where they are browsed by subdirectory.
  • problems in OpenProblemLibrary are maintained by a group of OPL editors. They may modify problems so that they conform to stylistic guidelines, or removed problems which are too similar to other OpenProblemLibrary problems.
  • Contrib problems are maintained by their original contributors. Problems in Contrib will not be changed or removed by editors.
  • OpenProblemLibrary editors review problems in Contrib, and copy selected problems into the OpenProblemLibrary.
  • Problems offered to Contrib are accepted as is.

So, problems can be added to Contrib for two purposes. If a problem author wants to share their work with other WeBWorK instructors, they can have them added to Contrib, all WeBWorK sites will get the problems when they update their copies of the OPL, and the problems will always be exactly as the problem author wants them. Secondly, problems in Contrib can be considered for addition to the OpenProblemLibrary. If the problems are copied in the OpenProblemLibrary, they will be more visible to users, but they may be modified over time by the OPL editors.

The mechanics of contributing to the OPL and Contrib

The basic process is

   git clone
   cd webwork-open-problem-library
   git remote add upstream
  • add and edit your problems to the Contrib subdirectory of webwork-open-problem-library
  • do not delete other problems in the repository (even if they are not needed for your site)
  • commit (if you have added files, git commit -a -m 'Descriptive message here' will add all new files which have appeared in your copy of the OPL)
  • push your changes back to YOUR github copy git push
  • issue a pull request to which asks the OPL maintainers to review your problems
    You do this from the web by visiting and looking for the pull request icon.

When adding problems, do not remove other parts of the OPL, even if you don't think they are relevant to you. If you do, removing the files becomes part of the pull request.

This procedure sounds more complicated than it is in practice. Once you have set up the accounts new problems can be added to your local file, uploaded to your github and submitted for consideration by the openwebwork OPL maintainers with just a few commands.

Identifying your contributions

The way github works you appear to be cloning and resubmitting the entire library although behind the scenes software is transmitting only your changes. This ensures that if you change both a macro file and a problem then they will both be uploaded and everything will stay in sync. It is also the reason why you should not delete other portions of the OPL which you are not touching. If you have changed other parts of the OPL your pull request will not be accepted.

For most contributors your best practice is to create a directory under Contrib (Contrib/myNewProblems) in your downloaded clone and add your problems there. "myNewProblems" is often the name of your institution but it could be your own name or handle if you prefer that. Inside Contrib/myNewProblems, please add a text file named README stating who is contributing the problems, and which github usernames are allowed to modify problems in Contrib/myNewProblems. This file should also contain any special information (if any) which sites should know when using these problems.

Problems submitted in the Contributor's directory are accepted quickly and not extensively checked for tagging, duplication and other editorial requirements. It is a good way to get your questions quickly viewed by the general public. Those curating the Open Problem Library will often select and possibly modify items in the Contrib directory for inclusion elsewhere in the OPL hierarchy. Editing and curating is not a quick process however so placing your contributions in the Contrib directory will get them "published" faster. They will also remain exactly as you uploaded them, while the copies moved into the other directories of the OPL may be modified to conform to editorial practices.

You can see the current organization of the Contrib directory here:

Indicating that you want your problems to be considered for the OPL

All new problems are submitted to the Contrib directory. If the person submitting problems wants their contribution to be considered for the OPL,

  • say that you want the problems considered for the OPL in your pull request
  • be sure that your problems are tagged. An editor will need to review the problems, and this helps us match problems with editors.
  • if a problem is similar to other problems in the OPL, add a MLT tag so the problem will be associated to a more-like-this group (to match the MLT tag in the similar problems)
  • give a brief explanation as to why these problems provide something not already present in the OPL

Note, improvements of existing OPL problems should be submitted by changing the current problem and making a pull request through github, rather than by creating a new problem.

Standards for problems contributed to the OPL

This section focuses purely on the technical standards for problems contributed to the OPL. We also hope that the problems contributed to the OPL will adhere to very high pedagogical standards as well. However, problems contributed to the OPL are not evaluated from that point of view. We leave it to the instructors using WeBWorK to determine which OPL problems will have the most pedagogical value in their particular circumstances.

Firstly, authors should make every effort to ensure that the problems they contribute have no bugs. In particular, authors should test problems using multiple seed values, and in hardcopy. Ideally, the problems contributed will actually have been used in a live class for a semester or more.

Secondly, authors should adhere to best practices for problem authoring. This includes use of MathObjects for defining and manipulating the mathematical objects in the problem and the use of PG language constructions for display constants and other formatting issues. In particular, authors should generally avoid direct use of HTML to format problems since this makes it impossible to print hard copy versions of the problems. The authoring documentation in this wiki has extensive information about this, including a very helpful index of problem techniques which illustrate best practices.

Thirdly, problem collections submitted to the OPL must be properly tagged.

Fixing bugs

If you plan to also use your git fork to contribute bug fixes for OPL problems, you can fix a bug and issue a pull request. If you are fixing a bug reported in Bugzilla, refer to the bug number in your pull request so the maintains can close the bug report.

Be careful of having multiple commits in a pull request. If you make a pull request, fix a bug somewhere else and try to issue another pull request before the first one gets merged, the two end up in one pull request. If the changes are connected, this makes sense. If they are unrelated, you will want to make the second set of changes in a branch. Pull requests from separate branches are automatically kept separate. This is most important if one of the pull requests is for the addition of problems since those take longer to check than bug fixes in problems.

Syncing your branch with the trunk

When using your branch to fix bugs in the OPL, you will want to make sure that your branch stays in sync with any changes to the trunk so you don't fix bugs that were already fixed. Also, new changes to the trunk will not automatically filter into your branch. To sync your branch with the trunk proceed as follows:

First, commit any recent changes to your branch. If your branch has any uncommitted local modifications, then the merging will fail. Then make sure you are in the root directory of your branch

$ pwd

and run

$ git pull upstream master

After running this, your branch working copy now contains new local modifications, and these new local modifications are duplications of all of the changes that have happened on the trunk since you first created your branch or since your last merge. Usually this will complete without any trouble and you can then commit the new changes to your branch. However, if you changed an OPL problem in your branch before the merge, and somebody else committed a change to that same problem in the trunk, then you will probably have to resolve a conflict.

Once you have resolved any conflicts you now have a working copy of the software on your machine which incorporates your changes and the changes in the trunk. The final step in the process is to commit your working copy to update your branch in the repository.

git commit -m "Merged latest trunk changes to my_branch."

It's a very good idea to do this regularly, and especially to do this immediately before fixing a bug in an OPL problem.

Reporting bug fixes

When you do fix a bug, be sure to say in the commit message "Fixed bug #XYZW". In fact, that is all you need to say. Then, find the bug again in Bugzilla, and add a comment on the bug to inform the assignee and anyone subscribed to that bug that you committed a fix. Be sure to indicate that the fix was committed in your branch and give the revision number. Once the fix is merged back into the trunk, the assignee will then close out the bug in Bugzilla.

Using Git

The use of Github is currently being tested. Users on MacOS may want to consider downloading the free SourceTree app from the App store. SourceTree is free. With GitHub, you can push changes for WebWork to your repository there and make these changes available to others. Once uploaded to github, you can request that WebWork management pull your change into the source code.

  • Go to and set up an account. You can choose the free open source option.
  • Follow the "Set up Git" instructions on the github site for setting up a ssh key. This is how you will authenticate when transferring files.
  • On the github site, search for "webwork" and select openwebwork. Select the component you want to work on (webwork2, pg, libraries, etc.) and then click on "Fork"--an icon in the upper right portion of the page.
  • When your fork has been created, you can choose to "Clone" a copy to your local computer using some git-compatible app (such as SourceTree).
  • Make your modifications on your local computer
  • When you are ready to submit your modifications "push" them to your private repository
  • From your repository choose the "pull request" button and ask that your contribution be incorporated into the repository for use by the WeBWorK community

See also

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