Re: [sca-assembly] ISSUE 6 - alternate proposal - Version 2 final tweaks

[Mike Edwards <mike_edwards@uk.ibm.com>]

Folks,


A couple of minor tweaks to address
comments by Michael Rowley and Simon
Nash.  Simon
raises an issue about using roles (Assembler, Deployer) as conformance
targets.  I suggest that we review this point under
ASSEMBLY-11 - Define Conformance
Targets.


Introduce a new subsection into the specification,
to follow line 330:

3.0.1 Specifying the Target Service(s) for a Reference

A reference may define one or more target services
which satisfy the
reference.  The target service(s) may be defined
in the following ways:


1) Through a value specified in the @target attribute
of the reference
element

2) Through a target URI specified in the @uri attribute
of a binding
element which is a child of the reference element

3) Through the setting of one or more values for binding-specific
attributes and/or child elements of a binding element
which is a child  
of the reference element


4) Through the specification of @autowire="true"
for the reference (or
through inheritance of that value from the component
or composite 
containing the reference)

5) Through the promotion of a component reference
by a composite reference
of the composite containing the component (the target
service is then 
identified by the configuration of the composite reference).


Some combinations of these different methods are not
allowed:

If @autowire="true" applies to the reference,
the autowire procedure is 
only used to find a target service if no target is
identified by any of the 
other ways listed above.  It is not an error
if autowire="true" applies to 
a reference and a target is also defined through some
other means.

If a reference has a value specified for one or more
target services in its
@target attribute, the child binding elements of that
reference MUST NOT  
identify target services using the @uri attribute
or using binding specific 
attributes or elements.

If a binding element has a value specified for a target
service using its
@uri attribute, the binding element MUST NOT identify
target services using 
binding specific attributes or elements.

It is possible that a particular binding type MAY
require that the address
of a target service uses more than a simple URI.  In
such cases, the @uri  
attribute MUST NOT be used to identify the target
service - instead, binding 
specific attributes and/or child elements must be
used.

Where the reference has a value specified in its @target
attribute, all the
binding types identified by the child binding elements
are available for use 
on each wire created implied by the @target attribute.


3.0.1.1 Multiplicity and the Valid Number of Target
Services for a
Reference

For references with multiplicity 0..1 or 0..n, it
is valid for the
reference to have no target service defined.

For references with multiplicity 0..1 or 1..1, it
is an error for the
reference to have more than 1 target service defined.

For references with multiplicity 1..1 or 1..n, it
is an error for the
reference to have no target service defined.

For references with multiplicity 0..n or 1..n, it
is valid for the
reference to have 1 or more target services defined.

The assembler or the deployer of a composite MUST
ensure that references 
are properly configured according to these rules.
 

For the error cases identified above, an error MUST
be generated by the SCA
runtime before the reference is invoked by the component
implementation. 

Some errors can be detected at deployment time.  For
example, where a 
composite is used as a component implementation, wires
and target services 
cannot be added to the composite after deployment.
 As a result, for  
components which are part of the composite, both missing

wires and wires with a non-existent target can be
detected at deployment
time through a scan of the contents of the composite.
 In these cases, an 
error SHOULD be generated by the SCA runtime at deployment
time. 

Other errors can only be checked at runtime.  Examples
include cases of 
components deployed to the SCA Domain.  At the
Domain level, the target of 
a wire, or even the wire itself, may form part of
a separate deployed 
contribution and as a result these may be deployed
after the original 
component is deployed.  In these cases, the SCA
runtime MUST generate an 
error before the reference is invoked by the component
implementation. 


For the cases where it is valid for the reference
to have no target service
specified, the component implementation language specification
defines the  
programming model for interacting with an untargetted
reference. 

Where a component reference is promoted by a composite
reference, the
promotion is treated from a multiplicity perspective
as providing 0 or more  
target services for the component reference, depending
upon the further  
configuration of the composite reference.  These
target services are in  
addition to any target services identified on the
component reference itself,  
subject to the rules relating to multiplicity described
in this section.


----------------------------------------------------------------------

Replace lines 274 - 280 with the following:

"A reference may identify one or more target
services which satisfy the
reference.  This can be done in a number of ways,
which are fully described  
in section "3.0.1 Specifying the Target Service(s)
for a Reference".

Replace lines 1424 - 1430 with the following: 

"A reference may identify one or more target
services which satisfy the
reference.  This can be done in a number of ways,
which are fully described  
in section "3.0.1 Specifying the Target Service(s)
for a Reference".

Replace lines 2372 - 2383 with the following:

uri  - has the following semantic

The uri attribute can be omitted.

For the binding of a reference, the uri attribute
defines the target URI  
of the reference.  This can be either the
componentName/serviceName for  
a wire to an endpoint within the SCA domain, or the
accessible address 
of some service endpoint
either inside or outside the SCA domain (where  
the addressing scheme is defined by the type of the
binding).

The circumstances under which the uri attribute can
be used are
defined in section 3.0.1 Specifying the Target Service(s)
for a  
Reference


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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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

---

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