RE: Web Services and transactions

Dieter

You are correct WSFL does not attempt to define the transactional semantics
that may span multiple Web services ( activities ) unlike XLANG. However the
accompanying WSEL ( endpoint definition language will cover QoS semantics
and others, it is not yet defined if this will include transactional
semantics also.

The coordination and termination protocol can be specified elsewhere
 unless you want to piggy-back ) transaction context with service
invocations ) but the demarcation has to be specified as part of the
business process and the alternative flows that come along with error
conditions surrounding the transactional of the process.

I believe BPMI is looking into the adoption of BTP (Business Transaction
Protocol) currently being worked on by an OASIS technical committee, there
is also a W3C submission pertaining to XLANG.

Regards,
-------------------------------------------------
Mark Potts
Chief Technology Officer
Talking Blocks
www.talkingblocks.com

t. 415 255 7424
f. 415 255 7425
c. 415 606 9096
e. mailto:mark.potts@talkingblocks.com
-------------------------------------------------


-----Original Message-----
From: www-ws-request@w3.org [mailto:www-ws-request@w3.org]On Behalf Of
Dieter E. Jenz
Sent: Monday, June 25, 2001 3:06 AM
To: www-ws@w3.org
Subject: Web Services and transactions


Hi,

The "transactions" issue seems to be virtually ignored in almost all
discussions that I am aware of. I'm viewing things from a business
process management perspective. In that context, Web services are
typically transactional.

The question needs to be answered how transactions can work in an
operational environment. I just want to illustrate my point using a
simple scenario.

Scenario: An activity (business process activity) is a Web Service,
which is implemented by an Enterprise JavaBean (EJB). With
container-managed persistence (CMP) the EJB container may independently
initiate a commit. If the process engine is not implemented as an EJB,
the Web Service EJB cannot "join" a transaction (i.e. the MANDATORY
transaction attribute would have no effect), which makes all the changes
caused by the EJB persistent. If the process engine crashes for some
reason, it will reestablish a consistent state upon restart, actually
resulting in the rollback of the activity. However, the activity
implementation has already committed. Consequently, the process engine
will schedule the activity for execution, resulting in the duplication
of work. (It might be able to declare the activity just rolled back as
"in doubt" and put the activity in "suspended" mode, however).

The above scenario triggers a lot of questions, for example:
- What happens if the process engine is implemented as an EJB? Then, the
process engine can initiate a transaction, which the activity
implementation can join. The inconsistency problem may not arise.
- What happens if some activity implementations are EJBs, some are COM
components, some are ...?

The problem space can become extremely complex, since entire business
processes can be exposed as Web services. In addition, Web services can
be composed of other Web services.

WSDL does not provide information on non-functional characteristics of
the service (e.g. QoS information). Also, there is no way do declare Web
services as transactional.

The overall goal of Web services, to enable application integration over
the Internet regardless of programming language or operating environment
would be severely compromised if it was not possible to solve the
transactions issue in a satisfactory way. Consider the above scenario:
just putting in a process engine implemented as an EJB would make a real
difference.

Are there any practical solutions already available (that I am unaware
of) or on the way?

Regards
Dieter