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Subject: RE: [sca-bpel] Issue 11 - BPEL variable initialization and SCA properties
- From: Mike Edwards <mike_edwards@uk.ibm.com>
- To: "OASIS BPEL" <sca-bpel@lists.oasis-open.org>
- Date: Wed, 12 Dec 2007 17:57:17 +0000
Folks,
I note that the problem of implementations
having computed default values exists for many languages.
It can happen in Java too, for example.
SCA can't hope to be able to represent such beasts. Perhaps
we simply need to acknowledge that a)
there IS a default but b) SCA can't introspect it. It
CAN be
overridden via SCA.
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
"Michael Rowley"
<mrowley@bea.com>
12/12/2007 17:28
|
To
| "Mark Ford" <mark.ford@active-endpoints.com>,
"Alex Yiu" <alex.yiu@oracle.com>
|
cc
| <sca-bpel@lists.oasis-open.org>
|
Subject
| RE: [sca-bpel] Issue 11 - BPEL variable
initialization and SCA properties |
|
The key question, for me, is
whether the component type should show non-literal default values. Imagine
reading a component type definition that looks like this:
<componentType>
<property
name=”x” defaultValue=”$y”/>
</componentType>
In this example, I’m assuming
that BPEL had an initialization expression for “x” that assigns it to
the value of the “y” BPEL variable. If you copy this into the component
type, the component type makes no sense, because there is no way to resolve
“y”.
That is why I said that only
literals can be used by the component type of a BPEL process.
Michael
From: Mark Ford [mailto:mark.ford@active-endpoints.com]
Sent: Tuesday, December 11, 2007 7:53 PM
To: Michael Rowley; 'Alex Yiu'
Cc: sca-bpel@lists.oasis-open.org
Subject: RE: [sca-bpel] Issue 11 - BPEL variable initialization and
SCA properties
The mustSupply text from the assembly
specification below SHOULD use the capitalized words from RFC 2119. It
would be better to say that the default-property-value MUST NOT be provided
when mustSupply="true".
That said I think the treatment
of BPEL variable initialization should be the same regardless of the form
of the from-spec. If I understand your proposal, you would treat an expression
from-spec differently than a literal from-spec.
After reviewing the Assembly spec
a little, I'm inclined to suggest that any value from the component overrides
the initialization from-spec for the variable in the BPEL. This seems consistent
with the goal of allowing the configuration of an implementation with externally
set data values. (Section 6.1 of the Assembly spec).
- Mark
From: Michael Rowley [mailto:mrowley@bea.com]
Sent: Thursday, November 01, 2007 5:58 PM
To: Alex Yiu; Mark Ford
Cc: sca-bpel@lists.oasis-open.org
Subject: RE: [sca-bpel] Issue 11 - BPEL variable initialization and
SCA properties
I looked at the Property section of
the Assembly Specification. It looks like what is there is OK. Here
it is:
mustSupply (optional) –
whether the property value must be supplied by the component that uses
the implementation – when mustSupply="true" the component must
supply a value since the implementation has no default value for the property.
A default-property-value should only be supplied when mustSupply="false"
(the default setting for the mustSupply attribute), since the implication
of a default value is that it is used only when a value is not supplied
by the using component.
It says that a default value should
be only be supplied when mustSupply is false, but it _doesn’t_
say that a default value MUST be supplied.
Perhaps we could add the following
to the SCA BPEL spec at line 357 (in the paragraph that describes the meaning
of sca:property=”yes”):
“If the variable has an initialization
expression (a from-spec) then that becomes the default value for
the variable in cases where the SCA component does not provide a value
for that property. If a value is provided for the property,
the expression is not evaluated. If the from-spec is a literal value,
where it has the following form:
<from><literal>literal
value</literal></from>
then the literal value will be represented
as the default value in the component type for the process. Any other
kind of initialization expression will not be represented in the component
type.”
Michael
-----Original Message-----
From: Alex Yiu [mailto:alex.yiu@oracle.com]
Sent: Tuesday, October 16, 2007 2:30 PM
To: Mark Ford
Cc: sca-bpel@lists.oasis-open.org; ALEX.YIU@oracle.com
Subject: [sca-bpel] Issue 11 - BPEL variable initialization and SCA properties
Issue entered.
http://www.osoa.org/jira/browse/BPEL-11
Regards,
Alex Yiu
Mark Ford wrote:
> TARGET: SCA Client and Implementation
Model Specification for WS-BPEL
>
> TITLE: BPEL variable initialization
and SCA properties
>
> DESCRIPTION: Is the target variable
allowed to have an initialization
> defined within the BPEL process
and if so, is this initialization ignored?
> It seems like the initialization
should be allowed but not executed in the
> case where a process is packaged
as an SCA and the property is provided by
> the component. It's probably also
worth pointing out that the variable must
> be an element or type variable.
Message variables cannot be initialized by
> an SCA property.
>
>
>
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