[OASIS Issue Tracker] Commented: (TOSCA-56) Improvement on the attribute "substitutableNodeType" of ServiceTemplate

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    [ http://tools.oasis-open.org/issues/browse/TOSCA-56?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=31309#action_31309 ] 

Thomas Spatzier  commented on TOSCA-56:
---------------------------------------

I think in the above proposal, the inheritance tree is looked at in the wrong direction, or the text is ambigous. I.e. one could think that if

C -> derives from -> B -> derives from -> A

and substitutableNodeType="B" that B and C could be substitued, where actually B and A can be substituted.

So my proposal for rewording that I will put into wd-12 would be:

This OPTIONAL attribute specifies a Node Type that can be substituted by this Service Template. If another Service Template contains a Node Template of the specified Node Type (or any Node Type this Node Type is derived from), this Node Template can be substituted by an instance of this Service Template that then provides the functionality of the substituted node. See section 3.5 for more details.

> Improvement on the attribute "substitutableNodeType" of ServiceTemplate
> -----------------------------------------------------------------------
>
>                 Key: TOSCA-56
>                 URL: http://tools.oasis-open.org/issues/browse/TOSCA-56
>             Project: OASIS Topology and Orchestration Specification for Cloud Applications (TOSCA) TC
>          Issue Type: Improvement
>          Components: Spec
>    Affects Versions: CSD05
>            Reporter: Paul Zhang
>
> The OPTIONAL attribute substitutableNodeType specifies the Node Type this Service Template can substitute, meaning that if another Service Template contains a Node Template of the specified Node Type, this Node Template can be substituted by an instance of this Service Template that then provides the functionality of the substituted node. 
> Consider the following scenario: 
> <ServiceTemplate id="example" substitutableNodeType="B">
> ...
> </ServiceTemplate>
> <NodeTemplate id="exampleTemplate" nodeType="A">
> ...
> </NodeTemplate>
> <NodeType name="A">
> ...
> </NodeType>
> <NodeType name="B">
>   <Derivedfrom typeref="A"/>
> ...
> </NodeType>
> According to the derived rule of NodeType, the ServiceTemplate "example" is capable to substitute the NodeTemplate "exampleTemplate".
> So, I suggest to explain this attribute like this: "This OPTIONAL attribute specifies the Node Type with an indication that the specified NodeType and the NodeTypes derived from can be substituted by 
>  this Service Template, meaning that if another Service Template contains a Node Template of the specified Node Type (or the NodeTypes derived from), this Node Template can be substituted by an instance of this Service Template that then provides the functionality of the substituted node."

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