This design of the DA protocol allows users to access persistent data through typed attributes. DDL specification appears as an interface with no operations but attributes declarations. So DDL-defined objects have interfaces and therefore Cobra objects have data object references. All these interfaces allow access and creation of associative grouping of objects. One may open, create, and copy a cluster.
Every cluster has a cluster ID, which can be queried and retured as a sequence.
But ODL is used instead of DDL, and it has its own program language mapping. DA and ODMG-93 are so close that they can implement and surport each other. If the data store use DDO protocol, the PDS can delegate directly to the CLI interface. This is always a topic in Distributed Database System. The essential property of the transactional execution model, which is called serializability model, is that it garantees isolation of concurrent transactions.