You
mentioned in the call today that you are in favor of allowing
elementType propertyAliases in correlation. My preference is to require
a messageType propertyAlias because I read the spec to say that all web service interactions
(<receive>, <invoke> ...etc) use a message variable for
sending/receiving data. In cases where the activity provides an element
variable or no variable at all (i.e. <fromPart>
or <toPart>) there is an anonymous WSDL message variable created
to send/receive the data. When the current spec refers to correlation
it talks about messages, not variables. As such, it seems consistent to
require a messageType propertyAlias.
If
you or others feel strongly that support for elementType attributes is
needed then I'd ask that you (or others) look at adding language to
handle the following cases:
1)
element variable used but elementType propertyAlias not available. Is
this an error or does the engine look for a messageType alias?
2)
single part message variable used but messageType propertyAlias not
available. Does the processor look for a suitable elementType alias?
3)
no variable used (<fromPart>, <toPart>). Do we select an
elementType or messageType first? What if both are found and they have
different <query> expressions? Is that an error?
I discussed this with Chris
Keller last week and he seemed to recall that this was already settled
by a previous issue. After doing a little research I found the
following issues which touch on this area:
Issue 145: Properties on
Non-Message Variables
-- This issue added support for
propertyAliases for elements and types. It does not discuss
correlation. Perhaps it was mentioned during the face to face in
Hawthorne?
If the intent was to allow
elementType propertyAliases for correlation then this has not made it
into the spec. Does anyone else recall
the discussion or can they point me to another issue that might address
this? Lastly, if I missed a part of the spec that covers this I'd
appreciate a pointer to it as well.
Thanks.
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Issue - 297 - Does correlation require a propertyAlias with
messageType attribute?
Status: received
Date added: 10 Jun 2006
Date submitted: 09 June 2006
Submitter: Mark
Ford
Description: I'd like a clarification as to the use of a
propertyAlias for message correlation. My reading is that the spec
requires a propertyAlias with a messageType in order to extract values
for correlation. In cases where an activity like a <receive> uses
an elementType variable for its data the spec explains that an
anonymous temporary WSDL message variable is created for the data and
its single part is used to populate the element variable on the
<receive>. The same wording (anonymous temporary WSDL message
variable) is used to explain <fromPart> and <toPart>
behavior.
If the intent is to allow propertyAlias with elementType then
we would need to define which propertyAlias would be used in the case
that there was a messageType and an elementType since they could have
different queries.
If the intent is to require a propertyAlias with messageType
then some additional text to Section 9.2 could make this explicit.
Submitter's proposal:
In Section 9.2, change
--- from ---
Observe that in order to retrieve correlation values
from a message, a processor needs to apply a particular
<propertyAlias> to the message. In the case in which the
application of the <propertyAlias> results in a response that
contains anything other than exactly one information item and/or a
collection of Character Information Items then a bpel:selectionFailure
fault MUST be thrown.
--- to ---
Observe that in order to retrieve correlation values
from a message, a processor MUST apply a <propertyAlias> with a
messageType value that matches the QName of the message. In the case in
which the application of the <propertyAlias> results in a
response that contains anything other than exactly one information item
and/or a collection of Character Information Items then a
bpel:selectionFailure fault MUST be thrown.
Changes: 10 Jun 2006 - new issue
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