AWSP (Asynchronous Web Services Protocol )
June 2002 (Historical Reference ONLY)
In April 2002 at the San Francisco meeting of WfMC, the AWSP
(Asynchronous Web Services Protocol was presented, discussed, and found
to meet all the goals that had been identified at the Muenster meeting.
These goals specifically were (Layer on top of SOAP, Use XML Schema
representation, Multiple Observers, Subscribe/Unsubscribe,Set process
instance data). Since that time: this work has evolved
into the ASAP technical committee of OASIS, and has been entirely
subsumed by that other work. Please use this document only for
historical reference, and refer instead to the ASAP working group (http://www.oasis-open.org/committees/tc_home.php?wg_abbrev=asap)
for current implementation information.
Below is a list of frequently asked questions.
What is the relationship between Wf-XML and ASAP
Wf-XML is designed and implemented as an extension
to the OASIS Asynchronous Service Access Protocol. ASAP provides a
standardized way that a program can start and monitor a program that
might take a long time to complete. It provides the capability to
monitor the running service, and be informed of changes in its status.
Wf-XML extends this by providing additional standard web service
operations that allow sending and retrieving the “program” or definition
of the service which is provided. A process engine has this behavior of
providing a service that lasts a long time, and also being programmable
by being able to install process definitions.
2 Why do we need a standard protocol for this?
Because it is anticipated that process editing
tools and process execution tools might be produced by different
vendors. A standard way to retrieve process definitions and send
definitions will allow a user to match the best process definition tool
with the best process execution engine for their needs. We already have
groups defining process languages to give a common way to express a
particular process definition. Wf-XML completes the job by giving a
standard way to pass the process definition between the design tool and
the execution engine.
3 Where did Wf-XML come from?
The roots of the current effort began in 1997 with
the Internet Engineering Task Force (IETF) effort named Simple Workflow
Access Protocol (SWAP) lead by Netscape, Oracle and others. This was
followed by the WfMC standard known as WfXML 1.0 and WfXML 1.1. Wf-XML
was implemented by a number of commercial products. Because it was
invented before SOAP, it does not use SOAP message structures. ASAP and
WfXML 2.0 are efforts to move the same capability to be on top of SOAP
messages, and to conform to other web standards that have come into
existence in the mean time.
4 What would Wf-XML be used for?
Wf-XML is an ideal way for a BPM engine to invoke
a process in another BPM engine, and to wait for it to completed.
5 How can Wf-XML be used by BP Design Tools?
Wf-XML provides a standard way to retrieve a
process definition from a BPM engine, and to provide an updated one to
the BPM engine. A process design tool could used this standard web
services based protocol to browse processes on remote BPM server. It
provides an interface between such a design tool and the BPM engine;
this is the traditional WfMC Interface 1 for getting and setting the
process definition. There is no other effort known to be proposed for
standardizing this interaction.
6 Does the protocol automatically convert the Process
No. The protocol merely communicates the process
definition to and from the client and server. The process design tool
and the process engine must be able to agree on a format to exchange.
7 How hard is it to implement?
At this point the underlying SOAP support is
readily available, and because this uses web service technology in a
normal way, it is quite easy to implement the 4 or 5 web service
operations that are needed.
8 Is it really a web service?
The common definition of a web service is that the
messages that are to be exchanged are defined using WSDL. Since Wf-XML
2.0 is defined using WSDL, we say that Wf-XML is a standard web
service. We have been careful to assure this because only by strict
adherence to the standard can we have the best chance to benefit from
all the other work being done on web service standards.
9 Is it compatible with Wf-XML 1.1?
No. The earlier protocol was not based on SOAP
messages. While it is based on many of the same ideas, we felt the
conformance to SOAP standards was more important than ability to
co-operate with earlier versions of the protocol.
Who is sponsoring the Demonstration of Wf-XML?
The Workflow Management Coalition (WfMC) is making the
arrangements for the demonstration, and the publication of the results.
Any additional questions - please email [email protected]