.. _openedx-tagging-adr-0002: 2. Tagging App structure ======================== Status ------ Partially accepted, partially obsolete (see note under "ObjectTag"). Context ------- We want the openedx_tagging app to be useful in different Django projects outside of just openedx-learning and edx-platform. Decisions --------- The openedx_tagging data structures and code will stand alone with no dependencies on other Open edX projects. Classes which require dependencies on other Open edX projects should be defined within a ``tagging`` module inside those projects. Taxonomy ~~~~~~~~ The ``openedx_tagging`` module defines ``openedx_tagging.models.Taxonomy``, whose data and functionality are self-contained to the ``openedx_tagging`` app. However in Studio, we need to be able to limit access to some Taxonomy by organization, using the same "course creator" access which limits course creation for an organization to a defined set of users. So in edx-platform, we will create the ``openedx.core.djangoapps.content_tagging`` app, to contain the models and logic for linking Organization owners to Taxonomies. Here, we can subclass ``Taxonomy`` as needed, preferably using proxy models. The APIs are responsible for ensuring that any ``Taxonomy`` instances are cast to the appropriate subclass. ObjectTag ~~~~~~~~~ Similarly, the ``openedx_tagging`` module defines ``openedx_tagging.models.ObjectTag``, also self-contained to the ``openedx_tagging`` app. But to tag content in the LMS/Studio, we need to enforce ``object_id`` as a CourseKey or UsageKey type. So to do this, we subclass ``ObjectTag``, and use this class when creating content object tags. Once the ``object_id`` is set, it is not editable, and so this key validation need not happen again. Note 2026-04-02: In 2024, `we simplified this `_, and ObjectTags are no longer subclassable. Instead, Django ``rules`` permissions hooks allow openedx-platform to extend the ``can_change_object_tag`` permission rule as needed. Rejected Alternatives --------------------- Embed in edx-platform ~~~~~~~~~~~~~~~~~~~~~ Embedding the logic in edx-platform would provide the content tagging logic specifically required for the MVP. However, we plan to extend tagging to other object types (e.g. People) and contexts (e.g. Marketing), and so a generic, standalone library is preferable in the log run. Changelog --------- 2026-04-02: * Added "Status" * Updated references to module paths