A flexible and pluggable versioning system for schema-oriented documents
Project description
zopyx.versioning
zopyx.versioning is a generic versioning system for schema-oriented content-objects (zope.schema, Archetypes, Dexterity etc.).
Why another versioning system?
Existing versioning approaches in the Zope world are:
CMFEditions
widely used
very monolithic
too tight integration with CMF
fragile implementation
doing “too much”
doing “too much” in a very intransparent way
no backend serialization format other than Python pickles
only ZODB-based backend
backend not pluggable
Basic concepts
golden rule #1: keep it simple, keep it small
pluggable storage API (storing the versioned data)
using JSON as data exchange format between objects to be versioned and versioner and between versioner and backend storage (the storage may use a different serialization format (e.g. ‘pickle’ for a ZODB based backend or ‘json’ for a typical noSQL backend like MongoDB)
making use of the Zope Component Architecture for adopting arbitrary content objects to the storage API
the solution does not claim to store and restore the complete state of an content object. Instead we focus on dealing with the metadata and the content itself. If an object uses a complex internal data model then it is in responsible to serialize and deserialize the data to JSON.
leave complex functionality (likely handling of references, object relations etc.) out of the core versioning engine - this might be handled through adapters implementing IVersionSupport.
Open points
should de-duplication be handled on the storage layer or the versioning layer (I assume on the storage layer as an optional feature in order to keep the overall complexity low)
all versionable objects must provide a unique ID (UID for Archetypes-backed content). How about Dexterity? How about ZTK/zope.schema-based content?
how deal with “large” content. E.g. a MongoDB-based backend has by default a 4MB limit for embedded documents (usually enough for standard content but not for binary content like images)
Changelog
0.1.0 (2010-07-09)
Initial release with MongoDB-based version storage
