notesmachine/server/nm-store/docs/storage.md

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# Storage layer for Notesmachine
This library implements the core functionality of Notesmachine and
describes that functionality to a storage layer. There's a bit of
intermingling in here which can't be helped, although it may make sense
in the future to separate the decomposition of the note content into a
higher layer.
Notesmachine storage notes consist of two items: Zettle and Kasten,
which are German for "Note" and "Box". Here are the basic rules:
- Boxes have titles (and date metadata)
- Notes have content and a type (and date metadata)
- Notes are stored in boxes
- Notes are positioned with respect to other notes.
- There are two positions:
- Siblings, creating lists
- Children, creating trees like this one
- Notes may have references (pointers) to other boxes
- Notes may be moved around
- Notes may be deleted
- Boxes may be deleted
- When a box is renamed, every reference to that box is auto-edited to
reflect the change. If a box is renamed to match an existing box, the
notes in both boxes are merged.
Note-to-note relationships form trees, and are kept in a SQL database of
(`parent_id`, `child_id`, `position`, `relationship_type`). The
`position` is a monotonic index on the parent (that is, every pair
(`parent_id`, `position`) must be unique). The `relationship_type` is
an enum and can specify that the relationship is *original*,
*embedding*, or *referencing*. An embedded or referenced note may be
read/write or read-only with respect to the original, but there is only
one original note at any time.
Note-to-box relationships form a graph, and are kept in the SQL database
as a collection of *edges* from the note to the box (and naturally
vice-versa).
- Decision: When an original note is deleted, do all references and
embeddings also get deleted, or is the oldest one elevated to be a new
"original"? Or is that something the user may choose?
- Decision: Should the merging issue be handled at this layer, or would
it make sense to move this to a higher layer, and only provide the
hooks for it here?