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Comment: Mention ContentLibraryTransformer


  1. Split Modulestore, which was modified to support content libraries. Instead of just storing "course" structures, Split Modulestore now has the concept of a "course-like" structure, which is either a course or a library.
    • Courses and libraries are implemented similarly, each with a directed acyclic graph (DAG) of XBlocks, and a history of all changes made. The graph of blocks for both courses and libraries are stored in the "structures" MongoDB collection.
    • Split's "active_versions" MongoDB collection stores a list of all course-like objects (courses and libraries). Each one has an ("org", "course", "run") triplet which is the unique ID of that course-like object. In that triplet, "org" is the organization that published the course-like object, and "course" is the field that stores the name ID value of the course-like object, which may be a library name; e.g. if the library's ID is "library-v1:UniversityX+LIB100", then "org" is "UniversityX" and "course" is "LIB100". Since libraries do not have the concept of "runs", the "run" value of a library is always set to "library." The other difference between courses and libraries in this collection is that courses have a "version" object that contains a "draft-branch" and/or "published-branch" entries (that point to the current version of the course DAG in the "structures" collection), whereas libraries only have a "library" entry (which points to the current version of the library DAG in the same "structures" collection).

      Screenshot of an "active_versions" collection, showing MongoDB documents for both a library and a course:
    • Any XBlock's Scope.content field values will be stored in split's "definitions" collection. A single definition document may be shared among any uses of that same XBlock in libraries and courses.
    • Documents in the split modulestore are considered immutable; any changes to content in a course or library result in a new version of the definition and/or structure object being created, and the active_versions record is then updated to point to the new versions. (This is just a note - this aspect of the modulestore was not changed when content libraries were added.)
  2. The Library Root XBlock, a simple structural XBlock analogous to the "course" XBlock. This XBlock is the root of each content library. It is found in the platform code at common/lib/xmodule/xmodule/ This block is just a container and does not have any user-visible functionality.
  3. "LibraryLocator" and "LibraryUsageLocator" opaque keys, which are identifiers used to uniquely identify libraries and the XBlocks that are contained within a content library. -
  4. Studio support for editing content libraries
  5. Studio Import/Export code allows exporting and importing content libraries as XML -
  6. The Randomized Content Block, an XModule that is used to show content from a library to students. In the code, the block is called the Library Content Module because the original intention was for it to support two "modes": randomized content and manually selected content. Since the latter mode was never implemented, the module's display name was changed to "Randomized Content Block."
  7. LibraryToolsService, an XBlock runtime service that provides some functionality that the Randomized Content Block (LibraryContentModule) needs in order to function, such as:
    • list_available_libraries(): used in the Randomized Content Block settings UI to allow the user to select which content library to draw content from.
    • get_library_version(): given a library ID, returns the current version number of that library.  Used to determine when new/updated content has been added to a library.
    • update_children(): described below in "How Components Are Copied Into the Course"

  8. ContentLibraryTransformer, a block transformer which allows Library Content modules to work with the Course Blocks API.

How Components Are Copied Into the Course