[OASIS Issue Tracker] Commented: (TOSCA-43) Type versioning

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    [ http://tools.oasis-open.org/issues/browse/TOSCA-43?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=30846#action_30846 ] 

Derek Palma commented on TOSCA-43:
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With TOSCA we have different type systems which need to evolve independently:

1) The TOSCA XML schema. Currently, this is the TOSCA-v1.0-wdXX.xsd file published with each draft. Its namespace URI (currently http://docs.oasis-open.org/tosca/ns/2011/12) denotes the schema and should be treated like any other OASIS standard xsd based schema.

2) The potentially unlimited Node/RelationShip/Artifact types which can be defined using the TOSCA language. Because these are encoded as XML documents, each document's namespace URI defines a TOSCA "type space" and can be evolved by changing the namespace URI to create a completely different set of types but superceeding the previous set of types in some convenient way. Note that if one desires to create a more specialized type based on an existing type, the TOSCA derivation mechanism should be used instead. The URI encoding convention for superceeding a previous schema need not be specified unless machine reasoning is required to identity related versions. I can't think of a use case where this would be needed at the moment since the XML namespace mechanism allows any subset of all available NS URIs to be consumed in parallel.

> Type versioning
> ---------------
>
>                 Key: TOSCA-43
>                 URL: http://tools.oasis-open.org/issues/browse/TOSCA-43
>             Project: OASIS Topology and Orchestration Specification for Cloud Applications (TOSCA) TC
>          Issue Type: Sub-task
>          Components: Spec
>            Reporter: Derek Palma
>
> Type versioning. A more general term is schema or type evolution. This idea would be applicable if a type A exists, and someone later wants to create a type A' which is intended to be like A but not A and not related in a typed manner . It is important to note that A' and A are completely different types with no way to reason the delta between them. If one wanted some type based on A, they'd create a subclass of A and specialize accordingly. The practical uses of schema versioning is usually to create a completely new set of types which offer a different set of semantics than the previous version, so this is more of a way of labeling schemas.

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