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Subject: Re: [sca-assembly] [ISSUE 16] Component URI is not well described. Proposal
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 > > > ------------------------------------------------------------------------ > > / > / > > /Unless stated otherwise above: > IBM United Kingdom Limited - Registered in England and Wales with number > 741598. > Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU/ > > > > > >
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