[OASIS Issue Tracker] Commented: (CAMP-32) CAMP needs to say something about the serialization of null attribute values and empty arrays

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    [ http://tools.oasis-open.org/issues/browse/CAMP-32?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=31906#action_31906 ] 

Tobias Kunze  commented on CAMP-32:
-----------------------------------

I am not sure I understand the need for this issue, perhaps because I disagree with the suggestion that servers should omit "empty" attributes. I would very much like to see explicitly when e.g. a PHP Platform Component has currently no extensions loaded ("extensions": []) rather than having to infer this from the fact that there is no "extensions" attribute.

If we agree on this, then everything is fine: resources with the same attributes are the same resource type and resources with different attributes are different resource types. Consider

    A = {k1: v1, k2: v2}
    B = {k1: v1, k2: v2, k3: v3}

A and B are different resources whereas B with v3 = "foo" and B' with v3 = "" are the same resource, just with different value. So, if I PUT B', the string "foo" gets changed to "". B' does not magically change to A.



> CAMP needs to say something about the serialization of null attribute values and empty arrays
> ---------------------------------------------------------------------------------------------
>
>                 Key: CAMP-32
>                 URL: http://tools.oasis-open.org/issues/browse/CAMP-32
>             Project: OASIS Cloud Application Management for Platforms (CAMP) TC
>          Issue Type: Improvement
>          Components: Spec
>            Reporter: Gilbert Pilz
>            Assignee: Gilbert Pilz
>
> The following JSON:
> {
>   "uri" : "http://slc03lgx.us.oracle.com/campSrv/Assembly/9";,
>   "name" : "/examples",
>   "description" : null,
>   "created" : "2012-11-14T08:33-0800",
>   "tags": []
>   ...
> }
> Is semantically equivalent to:
> {
>   "uri" : "http://slc03lgx.us.oracle.com/campSrv/Assembly/9";,
>   "name" : "/examples",
>   "created" : "2012-11-14T08:33-0800",
>   ...
> }
> However, different languages and mappings treat these representations in different ways. For the sake of interoperability we should consider avoiding these differences by adding requirements to CAMP regarding the serialization of empty arrays and non-existent values.
> We could:
> 1.) say that clients and servers MUST NOT send either 'null' attributes or empty arrays
> 2.) say that clients and servers SHOULD NOT send either 'null' attributes or empty arrays
> 3.) say that clients and servers MUST NOT send 'null' attributes and SHOULD NOT send empty arrays
> 4.) say that clients and servers SHOULD NOT send 'null' attributes and MUST NOT send empty arrays
> We could also blow out the above choices with the additional factor of allowing clients and servers to have different behavior. For example "Clients MUST NOT send 'null' attributes but servers SHOULD accept them". I've had experience with this sort of thing (in the WS-I profiles) and it rapidly gets weird. IMO it is naturally outside the scope of any specification to define how one party in an interaction should behave in the face of non-compliant behavior on the part of another party. If a CAMP service implementation wanted to be "generous in what it receives", it should be free to do that, but I don't think we can mandate that behavior.

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