IODMs

Immutable, content-addressable, reusable

##Definitions

##Objects

DataObjects are immutable and therefore must have a unique, non-reusable "identifier". This differs from the DataObjects current "key" accessed via a collection which can be reused. The key is used to reference the DataObjects identifier, thereby providing immutability constraints. Hashes are preferred because they can be consistently generated from the data itself; this also (TODO: hashes are ideal). For two IODMs to be compliant, the namespace of the algorithms used to generate the identifiers must not conflict.

For example, if I have a "BlogEntries" collection that stores the text of my blog posts, I might have one DataObject with a key that is the blog post title (e.g., "My Summer Project"_ with an identifier equal to the hash of the data in that entry (e.g., "My summer project was making a bla bla bla"). In this way, I can re-associate the key with a new DataObject (and therefore new identifier; i.e., editing the blog post but keeping the old version) or a new key with the same identifier (i.e., renaming the title of the blog post).

##OpLog

OpLog
  ref/uid

  object_key
  object_ref
  timestamp
  collection_ref
  operation
  operation_parameters

##Collections

A Collection is the interface to access a uniquely namespaced group of DataObjects. It access its state via snapshot, history via operation logs, and

Collection
  ref/uid
  name (Optional but recommended)
  create(key, data)
  read(key)
  update(key, data)
  replace(key, data)
  delete(key, data)
  rename(old_key, new_key)
  create_snapshot()
  rename_collection(name)
  get_identifier(key)

Operations

create
update
replace
delete
snapshot
rename
rename_collection

##Snapshot

Snapshot:
  get(key: str) -> ???
  list() -> ???
  apply_oplogs(*logs: Oplog) -> null
  load(snapshot: Snapshot) -> Snapshot (Classmethod)

A snapshot is an interface (and optionally datastructure) that stores the state of a collection at a given point in time. Most simply this is a list of keys and DataObject identifiers.

Store get set

Collection id get(key)

Object id data

Snapshots

Operations

fabianvf/iodm

IODMs

Operations