whitehall: Edition Model
This page documents only a subset of the full Document and Edition model world - it is a very complex area and any more detailed documentation risks being too complex to read, and it will rapidly become obsolete. The source code is the primary source of truth!
Note, as a simplification, that concerns are not shown. For instance Attachment is actually linked to an Attachable which is a concern mixed in by Publicationesque
Document
A document represents all iterations of a publishable document in Whitehall. It stores the main document type, the content_id which links it to the Publishing API and the slug, used to locate the document in web pages.
Each document can have multiple editions - they track the various major revisions of the document. One edition will be the latest_edition and one may be the live_edition if the document is currently published.
Edition
Edition is the parent of a whole forest of different classes that implement varying logic depending on the flavours of edition - the diagram only shows one, Publication for simplicity.
Editions have a state - see Edition Workflow for more on the state.
Attachment
Some editions, such as Publication and its siblings, have Attachments. These are either html attachments (created using GovSpeak markup), or files, or external attachments.
HTML Attachments are special, in that they have their own slug and content_id - they are handled separately by the Publishing API - see below.
Relationship to Publishing API model
Note that the Publishing API has its own detailed model documentation
Be aware that Documents and Editions in Whitehall do not always correspond directly with Documents and editions in the Publishing API
A Document in Whitehall has a content_id which corresponts to a content_id in a matching Document in the Publishing API.
However Editions do not match 1:1 - Whitehall editions may go through many drafts and revisions which are never published, so will not be stored in the Publishing API.
Also a HtmlAttachment is handled as a standalone Document - it has its own slug and content_id; when it is published, it becomes a new Document in the Publishing API, with its own editions and workflow.