ISSUE 16: Component URI is not well described

["Michael Rowley" <mrowley@bea.com>]

 

I’ve enclosed a proposed modification to section 9.2 to improve the description how URIs should be constructed.  The enclosed Word document has change tracking to show how it has changed.  I’ve also included it into the email, so that people can comment on or question specific sections as part of this email thread.

 

Note that this URI construction requires that there be a new optional @uri attribute on components.  The ability to specify a URI (which is usually relative) makes it possible to design the URI hierarchy independent from the structure of the domain, which I believe is valuable.

 

Michael

 

9.2 Form of the URI of a Deployed Binding

 

9.2.1 Constructing Hierarchical URIs

Bindings that use hierarchical URI schemes construct the effective URI with a combination of the following pieces (using a pseudo-BNF representation of its structure):

Implementation-Dependent Base URI / {Component URI /}⁺ Service Name / Binding URI?

 

Each of these components deserves addition definition:

Implementation-Dependent Base Domain URI .  SCA does not specify the content of the base URI that should be used for any deployed binding, except to say that it must be a hierarchical URI.  There is also no requirement that the base URI be the same for any two uses of it.

{Component URI /}⁺. This is a “/” separated sequence of the relative URIs specified by components (or the component name, if a URI is unspecified).  These are the relative URIs of the components, starting from the domain-level component and following down each of the <implementation.composite> components until reaching a component that exposes the service that the binding is for.  This means that promoted services get a URI which is computed based on the highest promotion of that service, not based on the lowest-level component that offered the service to be promoted.

Service Name. The service name is the name of the service that the binding is for, as defined by the component’s component type.

Binding URI.  The Binding URI is the relative URI specified in the “uri” attribute of a binding element of the service.  The default value of the attribute is value of the binding’s name attribute treated as a relative URI.  If the binding has neither a @uri nor a @name attribute, then the last path segment of the URI will not be present (i.e. it defaults to the empty string).

The binding URI may also be absolute, in which case the absolute URI fully specifies the full URI of the service.  Some deployment environments may not support the use of absolute URIs in service bindings.

The name of the containing composite does not contribute to the URI of any service, but the name of the higher-level component that uses the containing composite as an implementation is used instead.

For example, a service where the Base URI is "http://acme.com", the component is named "stocksComponent" and the service name is "getQuote", the URI would look like this:

http://acme.com/stocksComponent/getQuote

Allowing a binding’s relative URI to be specified that differs from the name of the service allows the URI hierarchy of services to be designed independently of the organization of the domain.

It is good practice to design the URI hierarchy to be independent of the domain organization, but there may be times when domains are initially created using the default URI hierarchy.  When this is the case, the organization of the domain can be changed, while maintaining the form of the URI hierarchy, by giving appropriate values to the uri attribute of select bindings.  Here is an example of a change that can be made to the organization while maintaining the existing URIs:

To move a subset of the services out of one component (say "foo") to a new component (say “bar”), the new component should have bindings for the moved services specify a URI “../foo/MovedService”..

The URI attribute may also be used in order to create shorter URIs for some endpoints, where the component name may not be present in the URI at all.  For example, if a binding has a uri attribute of "../myService" the component name will not be present in the URI.

9.2.2 Non-hierarchical URIs

Bindings that use non-hierarchical URI schemes (such as jms: or mailto:) may optionally make use of the “uri” attritibute, which is the complete representation of the URI for that service   binding. Where the binding does not use the "uri" attribute, the binding must offer a different mechanism for specifying the service address.

 

 

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URI Construction.doc