VOSpace 2.1 issues

[Matthew Graham]

Hi,

Mike Fitzpatrick and I were reviewing the VOSpace spec last week specifically for capability stuff and realized that there are a couple of elements missing that we would like to see included in VOSpace 2.1:

(1) At the moment you get all-or-none with the capabilities on a node whereas there should be a way to specify which capabilities you would like on a node so we would like to propose two additional methods to work a specific node: attachCapability and detachCapability.

(2) There is also no specific route for an error in a capability execution to be reported back to a user. For example, suppose a node has the capability that a VOTable uploaded to it will automatically be converted into a database table somewhere. In theory, the data transfer should complete only when the capability has successfully executed rather than just when the byte transfer component has completed. However, if there is an issue with converting the VOTable to a database table then the transfer should indicate that it failed but with what error message? Internal server issue? We would like there to be an additional error message for capability issues.

Really, it is quite surprising that these have not been thought of before but maybe now is when we are beginning to think about the capability aspects of the spec properly for the first time.

	Cheers,

	Matthew