Re: [sca-assembly] [NEW ISSUE] Wiring from a reference with no binding to aservice with a binding

[Simon Nash <NASH@uk.ibm.com>]

This issue raises a general point about what justification is needed in 
order to open an issue.

In general an issue should say that something is wrong and describe what 
the problem is.  It may also give a proposal for a change to resolve the 
problem.  The "something is wrong" could be an error or inconsistency in 
the spec, or it could be a real world use case that the spec does not 
address adequately.  I don't think an issue should be raised based on an 
opinion that says "I don't like spec rule X and I prefer rule Y instead."

With this issue I don't see any clear description of what is wrong with 
the current spec rules.  The spec appears to be clear and consistent as it 
stands.  All I see is an assertion that the rule in the current spec 
imposes an "unreasonable requirement".

Why is this spec rule unreasonable?  What real world use case has a 
problem because of this rule?  IMO the rule is fine as it stands, and no 
change is needed.  However, I'm prepared to be educated on this, and if 
the rule is causing a problem, then we we should look at the problem and 
see what spec change needs to be made to resolve the problem.  The 
solution could be the one proposed, or there could be a different 
solution.  Without a clear problem statement and use case to drive the 
discussion, the debate will come down to one person's technical opinion 
against another's, which is unlikely to be productive.

    Simon 

Simon C. Nash, IBM Distinguished Engineer
Member of the IBM Academy of Technology
Tel. +44-1962-815156  Fax +44-1962-818999



Mike Edwards/UK/IBM@IBMGB 
27/11/2007 15:42

To
"OASIS Assembly" <sca-assembly@lists.oasis-open.org>
cc

Subject
[sca-assembly] [NEW ISSUE] Wiring from a reference with no binding to a 
service with a binding







<This issue is transferred from the SCA Policy TC where it was dubbed 
POLICY-34> 

RAISER  Michael Rowley (original) 

TARGET:  SCA Assembly Specification 

DESCRIPTION: 

The algorithm in the policy spec says that it is _not_ possible to wire 
from a reference that does not declare a binding (i.e. uses binding.sca) 
to a service that declares one or more bindings. However, I think this 
should be possible. 

It is an unreasonable requirement to say that a service with a binding can 
only be the target of a reference that has that same binding. The default 
binding (binding.sca) should be treated as the "I don't care" binding, and 
should work with any binding available within the domain. Or, more 
precisely, any binding that can satisfy the required intents. 

Section 4.8.1 of  the Policy frmework spec states: 

The wiring compatibility algorithm below determines the compatibility of a 
wire by a pairwise choice of a binding instance and the corresponding 
policySets on each side of the wire. 

This should be changed to the following: 

If either side of a wire does not specify a binding (or explicitly 
specifies binding.sca) the wire is considered to be valid for the purposes 
of policy processing. If both sides of the wire use binding.sca then the 
policies will be determined by the union of the required intents of both 
sides (policy sets aren't used with binding.sca). Otherwise, the bindings 
and policies used for the wire will be determined by adding the intents 
that are required by the binding.sca end of the wire to the other end of 
the wire and then following the section 4.10 algorithm in the Polcy 
Framework. 

If neither side of the wire uses binding.sca, then the wiring compatibilty 
algorithm below is used for determining compatibility. Note that there may 
be many binding instances present at each side of the wire. This algorithm 
determines the compatibility of a wire by a pairwise choice of a binding 
instance and the corresponding policySets on each side of the wire. 

PROPOSAL: 

The following should be added to the Wires section of the Assembly 
specification: 

If either end of a wire does not specify a binding (or explicitly 
specifies binding.sca) the wire is regarded as valid.  In other words, 
binding.sca is regarded as being compatible with 
any other type of binding.  Where other types of binding are applied to 
each end of a wire, compatibility of the two bindings is determined by the 
specifications for the two bindings 
involved, allied to the intent and policies attached at each end.  In 
general, a wire which has two different binding types at each end (non 
binding.sca) is likely not to be valid. 

If both ends of the wire use binding.sca then the policies will be 
determined by the union of the required intents of both ends (policy sets 
aren't used with binding.sca). 
Otherwise, where one end of the wire uses binding.sca, the bindings and 
policies used for the wire will be determined by adding the intents that 
are required by the binding.sca end of the wire to the other end of the 
wire and then following the algorithm defined in the Policy Framework 
specification section 4.10. 

If neither end of the wire uses binding.sca, then the wiring compatibilty 
algorithm described in section 4.10 of the Policy Framework specification 
is used for determining compatibility. Note that there may be many binding 
instances present at each side of the wire. This algorithm determines the 
compatibility of a wire by a pairwise choice of a binding instance and the 
corresponding policySets on each side of the wire. 


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 












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