Connected Data Objects

Connected Data Objects (CDO) is a free implementation of a Distributed Shared Model on top of the Eclipse Modeling Framework (EMF).

With CDO, programmers can easily enhance existing EMF models in such a way that they can be stored and subsequently maintained in a central model repository. While object relational mapping against a JDBC data source on the server side is the shipped default, CDO provides for pluggable storage adapters that allow you to develop and use different mappers (like Hibernate- or OODB-based). On the client side, CDO provides a default integration with EMF, the Eclipse Modeling Framework, although other model integrations on top of the CDO protocol are imaginable as well.

Model integration features

 * EMF integration at model level (as opposed to the edit level)
 * Support for generated models (just switch two .genmodel properties)
 * Support for dynamic models (just load .ecore file and commit to repository)
 * Support for legacy models (for compiled models without access to .genmodel)
 * Support for the Ecore meta model and descendants

User interface features

 * Eclipse view for working with CDO sessions, transactions, views and resources
 * Package Manager dialog per session
 * Eclipse editor for working with resources and objects

Client side features

 * Multiple sessions to multiple repositories on multiple servers
 * Multiple transactions per session
 * Multiple read-only views per session
 * Multiple audit views per session (an audit is a view that shows a consistent, historical version of a repository)
 * Multiple resources per view (a view is always associated with its own EMF ResourceSet)
 * Inter-resource proxy resolution
 * Multiple root objects per resource
 * Object state shared among all views of a session
 * Object graph internally unconnected (unused parts of the graph can easily be reclaimed by the garbage collector)
 * Only new and modified objects committed in a transaction
 * Transactions can span multiple resources
 * Demand loading of objects (resources are populated as they are navigated)
 * Partial loading of collections (chunk size can be configured per session)
 * Adaptable pre-fetching of objects (different intelligent usage analyzers are available)
 * Asynchronous object invalidation (optional)
 * Clean API to work with sessions, views, transactions and objects
 * CDOResources are EObjects as well
 * Objects carry meta information like id, state, version and life span
 * Support for OSGi environments (headless, Eclipse RCP, ...)
 * Support for standalone applications (non-OSGi)

Network protocol features

 * Net4j based binary application protocol
 * Pluggable transport layer (shipped with NIO socket transport and JVM embedded transport)
 * Pluggable fail over support
 * Pluggable authentication (shipped with challenge/response negotiation)
 * Multiple acceptors per server

Server side features

 * Pluggable storage adapters
 * Multiple repositories per server
 * Multiple models (packages) per repository
 * Multiple resources (instance documents) per repository
 * Expressive XML configuration file
 * Configurable storage adapter per repository (see below)
 * Configurable caching per repository
 * Clean API to work with repositories, sessions, views, transactions and revisions
 * Support for OSGi environments (usually headless)
 * Support for standalone applications (non-OSGi)

DB store features

 * Supports all optional features of the CDO Server
 * Pluggable SQL dialect adapters
 * Includes support for Derby, HSQLDB, MySQL and Oracle (TBD)
 * Pluggable mapping strategies
 * Includes horizontal mapping strategy (one table per concrete class)
 * Includes vertical mapping strategy (TBD, one table per class in hierarchy)
 * Supports different mapping modes for collections