Should distinguish bookkeeping, data distribution and data transfer use cases

Bookkeeping.
------------

We are only concerned about data distribution and transfer. The connection to 
  bookkeeping is by mean of dataset.

Data Distrubutions.
-------------------

Operates in terms of data sets. Passes file names down to Data Transfer.
I don't see how use cases for Tier C, A in all directions are different
  from each other, especially given that each tier c will have a bookeeping
 system same as tier a.

General: 

Importer uses "pull" for transferring data from Tier A to Tier C.

Exporter wants to use "push" for transferring data produced locally into Tier A.

Combined use case for selection 1,2,3 and 4,5,6 from Adil's (per Tim)

1) The importer wants to select dataset to copy. Selection creteria may be:

- dataset name, collection names, any physics createria (decay mode etc), 
  group (AWG, Breco etc), type of production (SP, PR), good runs.

- component (micro, mini, navigational etc), time (including variouse time 
  options like since/after)


2) Importer wants to obtain the size of selected data set.

3) Importer wants to split data set into smaller sets for transfer to 
  accomodate to low disk cache space.

4) Importer wants to (dynamically) prioritise transfer of one data set over 
  another, including prioritizing subsets withing the data set.

5) Importer wants to make data available at his site as data is being imported.

6) Importer wants to know where data is coming from.

Data Transfer.
--------------

Doesn't know about data sets. Operates with bare files. The division
  between Data distribution use case and data transfer use cases is
  rather blurry, depends on implementation. Data transfer Module should be
  interfacable with local mass storage and possible implement automatically
  splitting datasets for the purpose of efficient transfer.

1) Importer wants to start/stop/pause/resume data transfer.

2) Importer wants to observ the transfer progress, in regular intervals or on 
  demand.

3) Importer wants to be notified on transfer success/failures.

4) Importer wants full info about complete transfer: what was copied, how long 
  it took, when started, what the transfer rate was.

5) Importer wants the freedom to place data where they see fit.

6) Importer wants to re-copy set of data.