[glue-wg] Extending GLUE 2.0 for Cloud services

[JP Navarro]

On Dec 4, 2013, at 7:31 AM, <stephen.burke at stfc.ac.uk> <stephen.burke at stfc.ac.uk> wrote:

> <snip>
> I think there are several different things here:
> 
> o Should we call an update GLUE 2.1? I would say yes, because it will be a new version of the complete schema - at least in LDAP we have the whole thing in one file so it gets updated as a unit. Anyway I think it would get messy to keep track of updates otherwise - if the cloud part is separate we will need a separate version for it. And if we did then update the base classes at a later date what would we do with the cloud part, since any inherited attributes could change?

In a change/version summary we can even highlight that the 2.1 introduces Cloud entities and doesn't (significantly) change previous 2.1 entities.

> o Should we put the whole thing in a single document or have an extension/update document? Either would be possible, but it seems cleaner to me to have a single document with a new major section for the cloud entities as we already have for compute and storage. Then you have one place to look for everything. Also we have some known mistakes in the existing document and this gives a chance to fix them, and there may be some places where the language can be improved, e.g. Salvatore wants to change "files" to "data objects". We should of course have a detailed change log.

It is a single schema.

> o Should we change anything in the existing entity definitions? That's probably the hardest thing as it risks opening a big can of worms. On the other hand, there may be some justified changes, e.g. to put back the min and max file - oops, data object - sizes in the StorageShare. Also the schema was mostly defined in 2007 and is untouched since early 2009 - the entire history of GLUE 1 evolution took five years! - so it wouldn't be surprising to have some justified changes as a result of subsequent experience or developments. In general terms it's relatively safe/easy to add new optional attributes to existing objects, as it doesn't affect the existing deployed system - that's what we always did for GLUE 1 evolution. However, we have the usual problem that updates take a long time to be deployed so no-one should expect to use new attributes any time soon, and experience suggests that agreeing even a single attribute can take a lot of discussion. I would therefore suggest that any update should be restricted to at most a handful of new optional attributes with a clear justification which has a broad acceptance.

Agreed, and making sure none of the changes cause incompatibilities with 2.0 based implementations.

JP