RE: [sca-j] NEW ISSUE: When is a RequestContext available?

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

Folks,

This conversation indicates a problem
with our terminology, which we need to sort out.

An SCA Component is indeed a configured
instance of an Implementation - and a single
implementation may be used by multiple
Components.

However, in Simon's original wording,
"instance" was not being used in that sense at all.
In Simon's wording, "instance"
referred to a runtime instance - a particular instantiation of
a particular component.  In Java,
this would mean a particular Java object.  Simon's wording
was correct in that sense, but it clearly
caused confusion for some folks.

Can I suggest that we use a term such
as "runtime instance" for this case?


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

Simon Nash/UK/IBM@IBMGB

30/01/2008 21:32

To	sca-j@lists.oasis-open.org
cc
Subject	RE: [sca-j] NEW ISSUE: When is a RequestContext available?

Sanjay,
Thanks for the pointer and for putting me straight on the terminology.
 If 
a component is an instance (Appendix C) then just calling it a component
should be enough, but perhaps "component instance" is clearer.
 I agree 
that the term "instance of a component" that I was using is incorrect.

    Simon

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



"Patil, Sanjay" <sanjay.patil@sap.com> 
30/01/2008 20:21

To
Simon Nash/UK/IBM@IBMGB, <sca-j@lists.oasis-open.org>
cc

Subject
RE: [sca-j] NEW ISSUE: When is a RequestContext available?







The Appendix C of the Assembly specification is the closest I can think
of for a glossary of the terms.

The Assembly specification in several places makes statements on the
lines of - A component is a configured instance of an implementation. So
I guess a component itself is an instance. So calling a component
instance as just that (that is - 'the component instance') may be better
than calling it 'an instance of the component' (which I believe
incorrectly hints at the possibility of multiple instance of the same
component). Now there is a possibility of multiple instances of the same
component in the implementation hierarchy (via implementation.composite)
of the SCA domain, but I guess you were not referring to that case. 

BTW, I searched the Assembly spec for all occurrences of the term
'instance' and couldn't find the term used for indicating 'instance of
a
component' anywhere.

I get a feeling that we are now on the path of splitting hairs :-)

-- Sanjay

> -----Original Message-----
> From: Simon Nash [mailto:NASH@uk.ibm.com] 
> Sent: Wednesday, Jan 30, 2008 11:55 AM
> To: sca-j@lists.oasis-open.org
> Subject: RE: [sca-j] NEW ISSUE: When is a RequestContext available?
> 
> Sanjay,
> Here's my terminology model:
> A component is a configuration of an implementation.
> There can (in general) be many instances of an 
> implementation.  Each of 
> these instances is configured by the component.
> Invocations to a component (via a service) are dispatched to 
> an instance 
> of the component
> In the above, I said "...instance of the component" rather
than 
> "...instance of the implementation" because the instance
has had the 
> component's configuration applied to it
> 
> Is there an SCA glossary somewhere that provides approved 
> definitions of 
> the above terms?
> 
>     Simon
> 
> Simon C. Nash, IBM Distinguished Engineer
> Member of the IBM Academy of Technology
> Tel. +44-1962-815156  Fax +44-1962-818999
> 
> 
> 
> "Patil, Sanjay" <sanjay.patil@sap.com> 
> 30/01/2008 18:12
> 
> To
> Simon Nash/UK/IBM@IBMGB, <sca-j@lists.oasis-open.org>
> cc
> 
> Subject
> RE: [sca-j] NEW ISSUE: When is a RequestContext available?
> 
> 
> 
> 
> 
> 
> 
> Just a nitpick -  You have used the term 'an instance of the
> component'
> a few times below. I would have thought that a component itself is
an
> instance (of an implementation). Perhaps replacing 'an instance of
the
> component' with 'the component instance' would be more appropriate!
> 
> Regarding the issue and the proposal - both make sense to me.
> 
> -- Sanjay
> 
> > -----Original Message-----
> > From: Simon Nash [mailto:NASH@uk.ibm.com] 
> > Sent: Wednesday, Jan 30, 2008 6:11 AM
> > To: sca-j@lists.oasis-open.org
> > Subject: [sca-j] NEW ISSUE: When is a RequestContext available?
> > 
> > RAISER: Simon Nash
> > 
> > TARGET: SCA Java Annotations and APIs Section 7.1: ComponentContext
> > 
> > DESCRIPTION:
> > 
> > The decription of ComponentContext.getRequestContext() says 
> in lines 
> > 647-648 that it returns null if "... there is no current
> > request or if the 
> > context is unavailable".  The situations where this
applies 
> > need to be 
> > defined more precisely.  Here are some cases where a request
> > context may 
> > or not be available:
> > 1. Within a business method for a service of the component.
> > 2. Within a property or reference injection setter method for
> > an instance 
> > of the component.
> > 3. Within a constructor for an instance of the component.
> > 4. Within an Init or Destroy method for an instance of the 
> component. 
> > 
> > In case 1, it seems clear that getRequestContext() will 
> always return 
> > non-null.  In the other cases, it is not clear what should
be 
> > returned.
> > 
> > PROPOSAL:
> > 
> > getRequestContext() MUST return non-null for case 1 and 
> > SHOULD return null 
> > for cases 2 through 4.
> > 
> > 
> > Simon C. Nash, IBM Distinguished Engineer
> > Member of the IBM Academy of Technology
> > Tel. +44-1962-815156  Fax +44-1962-818999
> > 
> > 
> > 
> > 
> > 
> > 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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