A simplistic, Datomic inspired, SQLite backed, REST influenced, schemaless auditable facts storage.

Fun, buzzwordy and possibly useful!

Data + Atom = Datom

A datom has 4 properties:

• entity: the thing you want to record information about (akin to primary key).
• attribute: a label for the information you want to record.
• value: the information itself (JSON serializable).
• time: when datom was stored.

Lets begin:

>>> from datoms import Datom
>>> datom = Datom('entity', 'some/attribute', 'value')
>>> datom.time is None
True

A datom (a fact) is immutable!

>>> try:
...     datom.entity = 'immutable' #doctest:+ELLIPSIS
... except AttributeError, e:
...     pass
>>> e.message
"can't set attribute"

Datoms

Datoms is where you store datoms.

>>> from datoms import Datoms
>>> datoms = Datoms()

With no argument the datams are stored in memory only, with a filename they are persisted to disk.

>>> datoms = Datoms('persisted.datoms') #doctest:+SKIP

POST

To store a datom you post it.

>>> datoms.post(datom)

If the datom had its time property set it will be replaced in storage by the UTC time at insertion.

You can think of Datoms as an append only collection of facts.

GET

To retrieve data from a Datoms you use get.

The bare minimum is to call get with an entity which returns a list of datoms belonging to entity. It returns the latest known facts about entity i.e. the latest value of every attribute attached to entity.

>>> datoms.get('entity') #doctest:+ELLIPSIS
[Datom(entity=u'entity', attribute=u'some/attribute', value=u'value', time=datetime.datetime(...)]

get returns an empty list if the entity is not known or all its attributes have been deleted.

When called with en entity and and attribute it returns the latest matching Datom.

>>> datoms.get('entity', 'some/attribute') #doctest:+ELLIPSIS
Datom(entity=u'entity', attribute=u'some/attribute', value=u'value', time=datetime.datetime(...)

get returns None if there is not matching Datom.

DELETE

Immutably! What?

You cannot ever delete a fact from a Datoms instance, but you can void it i.e. make it not show up when calling get.

>>> datoms.post(Datom('entity', 'void/soon', True))
>>> len(datoms.get('entity'))
2

To void just delete:

>>> datoms.delete('entity', 'void/soon')
>>> len(datoms.get('entity'))
1

You can also void an entire entity.

>>> datoms.delete('entity')
>>> len(datoms.get('entity'))
0