Re: [sca-assembly] [ISSUE 16] Component URI is not well described. Proposal

[Simon Nash <oasis@cjnash.com>]

Mike,
This looks good, and in line with previous discussions.  One very minor
suggestion: in the <alias/> element, rename the actualUri attribute to
targetURI (note capitalization).  Alternatively we could use structuralURI,
but this is a bit more of a mouthful.

   Simon

Mike Edwards wrote:
> 
> Folks,
> 
> I took an action to pull together a resolution for Issue 16 based on 
> previous discussions.
> 
> This is the proposal.
> 
> High Level:
> 
> It is proposed that SCA defines 2 URIs:
> 
> 1) */structuralURI/*
> 2) */bindingURI/*
> 
> *_structuralURI_*
> 
> Structural URI is a URI that describes each use of a given component in 
> the Domain.  It is never
> specified explicitly, but it calculated from the configuration of the 
> components configured into the
> Domain.  
> 
> The structural URI may be used to separately identify each use of a 
> component - for
> example, the structural URI may be used to attach different policies to 
> each separate use of a
> component.
> 
> For components directly in the domain, the structural URI is simply the 
> name of the component.
> 
> Where components are nested within a composite which is used as the 
> implementation of a
> higher level component, the structural URI consists of the name of the 
> nested component prepended
> with each of the names of the components upto and including the domain 
> level component.
> 
> For example, given a component named Component1 which is part of 
> Composite1 used as an
> implementation by Component2 which is part of Composite2 which is itself 
> used as the implementation
> of Component3 which is at the domain level, the structural URIs are as 
> follows:
> 
> a) Component1:    Component3/Component2/Component1
> b) Component2:    Component3/Component2
> c) Component3:    Component3
> 
> The structural URI can also be extended to refer to a specific service 
> of a component, by appending
> the name of the service to the component's structural URI.
> 
> *_bindingURI_*
> 
> SCA Bindings specifications can choose to use the structural URI defined 
> above to derive some binding
> specific URI according to some Binding-related scheme.  The relevant 
> binding specification describes
> this.
> 
> In addition, <binding/> elements have an optional @URI attribute, which 
> is termed a bindingURI.
> 
> If the bindingURI is specified on a given <binding/> element, the 
> binding may use it to derive an
> endpoint URI relevant to the binding.  The derivation is binding 
> specific and is described by the
> relevant binding specification.
> 
> For binding.sca, which is described in the SCA Assembly specification, 
> this is as follows:
> 
>  If the binding uri attribute is specified on a reference, it identifies 
> the target service in the SCA domain by
> specifying either the service's structural URI or an alias for the 
> structural URI.  
> If the binding uri attribute is specified on a service, it is ignored.
> 
> 
> *_structural URI Aliases_*
> 
> structural URIs can be used for a number of purposes.  Concentrating on 
> their use for administration
> and management purposes, it is required that a given component instance 
> can be given a URI
> which does not change even if the structure of the artifacts in the 
> domain does get changed.
> 
> This "unchanging" URI is called a "URI Alias" - effectively it is a "fixed"
> URI that maps to a specific structural URI - it is a kind of Map.
> 
> 
> URI Aliases are declared at the Domain level - in a Definitions file.  
> 
> Each Alias is declared using an <alias/> element as a child of a
> <definitions/> element (logically at the Domain level):
> 
> <alias aliasURI="xs:string" actualUri="xs:string"/>
> 
> - this is a simple mapping from the (unchanging) aliasURI to the actual
> structural URI of some component
> 
> - if the component moves due to some deployment activity, the aliasURI 
> remains unchanged and stable,
> but the actualURI needs updating to point to the new location of the 
> component.
> 
> 
> Detailed Proposal:
> 
> This will take a lot of engineering of a spec document.
> I will do this once we agree on the high level stuff above.
> 
> 
> Yours,  Mike.
> 
> Strategist - Emerging Technologies, SCA & SDO.
> Co Chair OASIS SCA Assembly TC.
> IBM Hursley Park, Mail Point 146, Winchester, SO21 2JN, Great Britain.
> Phone & FAX: +44-1962-818014    Mobile: +44-7802-467431  
> Email:  mike_edwards@uk.ibm.com
> 
> 
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