I'm a little confused as to the purpose of
default-property-value in the assembly spec. Is this value supposed to convey
what the default is within the implementation if no value is provided by the
configuration? If this is the case, then I agree with Najeeb and I better
understand Michael Rowley's desire to treat expressions differently than
literals.
However, it's not clear to me that this is what the
default-property-value is supposed to convey. My first reading of it was that it
was the value used if the composite didn't supply a value and not
necessarily a value that was introspected from the
implementation.
From: Najeeb Andrabi [mailto:]
Sent: Wednesday, December 12, 2007 2:45 PM
To: Michael
Rowley
Cc:
Subject: RE:
[sca-bpel] Issue 11 - BPEL variable initialization and SCA
properties
Hi Michael,
I think it impossible to determine which initialization expression initializes
the variable in case of complex BPEL process having conditional/concurrent flows
with multiple initialization expression of the same variable. In my view, we
should state that “if the literal value can be determined by static analysis of
the process then it will be represented as the default value in the component
type for the process”
Thanks,
Najeeb
From: Michael
Rowley [mailto:]
Sent: Wednesday, December 12, 2007 9:29
AM
To: Mark Ford; Alex
Yiu
Cc:
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:]
Sent: Tuesday, December 11, 2007 7:53
PM
To: Michael Rowley; 'Alex Yiu'
Cc:
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:]
Sent:
Thursday, November 01, 2007 5:58 PM
To: Alex Yiu; Mark Ford
Cc:
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:]
Sent: Tuesday, October 16, 2007 2:30
PM
To: Mark Ford
Cc: ;
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.
>
>
>
