Bundling and other approaches to mapping accessions/logical entities to DRS/ physical objects

[ianfore]

There is a need to explore the use of bundling as an approach to dealing with complex objects in DRS.

Cross referencing to to ga4gh/cloud-interop-testing#104 which has the details of a worked example using SRA.

See also raising this issue at TASC ga4gh/TASC#22

[ianfore]

The difference in approaches has been illusrated in this Jupyter notebook using an SRA example.

An imaging example has been used to illustrate maintaining the logical structure of collections of bundles in an external model. This allows DRS to remain a simple foundational protocol for access to physical objects in the cloud.