...

• Large delta before the new functionality is usable by courses
  • Need a minimal set of pure XBlocks before one could actually run a course
  • Need to write data bindings for FieldData
    • This could be a port of SplitModuleStore
    • This could be a new data storage format
• Need to update all places in LMS and Studio that use Modulestore to use the new pure runtime
  • Unclear whether all modulestore functionality can even be supported yet by a pure XBlock system

...

Glossary

XModule

The precursor to XBlock. This class is responsible for generating a student-facing HTML rendering of course content. It is bound to a particular student on instantiation.

XModuleDescriptor

The second half of the precursor to XBlock. This class is responsible for generating an HTML rendering for editing course content. It has no associated student information. As part of the backwards-compatibility layer between XModules and XBlocks in edx-platform, this class will actually proxy a number of attributes through to an instantiated XModule, so that edx-platform only has a single object that responds to methods/attributes for both XModule and XModuleDescriptor (this provides an interface consistent with XBlock, which is only a single object for both responsibilities).

DescriptorSystem

This class provides an interface between XModuleDescriptors and the rest of edx-platform. The intention is to abstract the XModuleDescriptor away from the details about how external systems are implemented.

ModuleSystem

As with DescriptorSystem, this class exists to provide an interface between the XModule and the rest of the LMS. It has become a dumping ground for many responsibilities, which will in the future be abstracted as XBlock services instead.

"Pure" XBlock

This is used to mean an XBlock that uses none of the XModule or XModuleDescriptor methods, and access none of the DescriptorSystem or ModuleSystem interfaces to access edx-platform.