Page Comparison

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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.

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This is used to mean an XBlock that uses none of the doesn't inherit from XModule or XModuleDescriptor methods, and access accesses none of the DescriptorSystem or ModuleSystem interfaces to access edx-platform.