[glue-wg] Capacity representation

[Sergio Andreozzi]

Burke, S (Stephen) wrote:
> On the Capacity issue, I think one source of confusion is that the
> current document shows a single Capacity with three lines linking it to
> share, MappingPolicy and Environment. That's misleading, because a
> single instance of Capacity can only ever be linked to one of those. 
I totally agree. The current StorageCapacity was concieved mainly as a 
"define once" block for a set of attributes.
The current UML implies that an instance of StorageCapacity can be 
contemporary linked to many different entities.

If we want to keep a common definition for the set of attributes which 
are in the storageCapacity class, then we could do it.
But this should be treated as an abstract class from which other classes 
inherits the common attributes.

I do not see really big advantages for this, therefore your proposal of 
three different/independent classes could be considered.
> For
> this kind of thing I think it would be better to have three separate
> Capacity boxes, each linked to only one other object, to make it clear
> that Capacity is an attribute of some other thing (the Capacity of this
> Share, etc). In fact the link to MappingPolicy shouldn't be there at all
> because it's another example of the same kind of thing: a Mapping Policy
> is an ACL, which has no independent existence, it's also just an
> attribute of something else (Share in this case). There are other things
> in the schema which behave like that, e.g. Location (you can only talk
> about the Location of some other thing).
>   
I understand that this was added to deal with the issue of a "Shared 
Share", i.e., what is the used size by a certain userDomain if different 
userDomains can access the same storageShare?
how would you address this?

- Sergio



>   (You could say that UniqueID is an extreme example of this - many
> things have a UniqueID attribute, but by definition they are all
> different.)
>
> Stephen
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>   


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Sergio Andreozzi
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