Re: [camp] Use of Cardinality for JSON array attributes

[Anish Karmarkar <Anish.Karmarkar@oracle.com>]

On 02/17/2013 03:41 AM, Alex Heneveld wrote:
> Tom, All-
>
> What about just having a boolean "required" in place of cardinality ?
>
> Where the type is an array it is clear that multiple values might be
> within the array.  But my read is that the "cardinality" is still either
> 0 or 1, so the combo of required + type.isArray gives the same
> information, in a clearer way.  (I also think cardinality >1 could be
> taken to mean that the _attribute_ might be listed twice, which is not
> our intention.)
>
> On a related note, I'd like to see the "mutability" attribute be made a
> boolean (in 5.2.2) rather than having values "immutable" and "mutable".
> Probably change the name of the field to be "mutable" rather than
> "mutability".

See my comment in the issue 
https://tools.oasis-open.org/issues/browse/CAMP-34

The terms mutability and writable are problematic wrt semantics of PUT.
We ought to talk about 'changeability' of attributes.

-Anish
--

> So 5.2.{1,2,3} would now be "Required", "Mutable", and "Writeable", all
> booleans, nice and simple and consistent.
>
> --A
>
>
> On 17/02/2013 05:06, Mr. Tom Rutt wrote:
> > For some reason I could not get access to raise a new Jira issue.
> >
> > I am sending this email for discussion before a formal issue is raised.
> >
> > There are several attributes defined with an array type (e.g, String[]
> > . Link[])
> >
> > These attribute definitions have various cardinality values,
> > including, 1, 0..1, or 0..*
> >
> > It makes no sense for an array attribute to have cardinality 0..*, for
> > this implies multiple arrays in the JSON serialization.
> >
> > In the case of 0..1 cardinality, Is there a difference in having an
> > array present with 0 elements, versus not having the array present?
> >
> > In the case of 1 cardinality, is it allowed to have an array with 0
> > elements present for its serialization?
> >
> > There does not seem to be a way to specify that an array should not be
> > present in the serialization with zero elements.  What is the
> > difference between no attribute in the serialization, verses an array
> > attribute with no elements?
> >
> > Proposal:
> >
> > Lets make the cardinality property of an attribute express the actual
> > semantics of presence.
> >
> > If the cardinality is 1 it should imply that the attribute is always
> > present, and sent as a basic type value.
> >
> > If the cardinality is 0..1, it should imply the attribute may be
> > present, and if present is sent as a basic type value.
> >
> > If the cardinality is 1…*, it should imply that the attribute is
> > alwasy present and sent using an JSON array.  The type in the
> > definition should be the base type (e.g, change Link[] to Link in the
> > definitions of type)
> >
> > If the cardinality is 0..1, it should imply that the attribute may or
> > not be present,  If present it is sent using a JSON array. It could be
> > constrained to not send empty arrays. The type in the definition
> > should be the base type (e.g, change Link[] to Link in the definitions
> > of type)
>
>
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