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Hi Keith,
Thanks for informative post.... Here's a key message
describing relationship
What is the relationship between BPMN and BPEL?
BPEL is an XML-based language for describing a business
process in which most of the tasks represent interactions between the process
and external Web services. The BPEL process itself is represented as a Web
service, and is realized by a BPEL engine which executes the process
description. BPMN is a standard set of diagramming conventions for
describing business processes. It is designed to visualize a rich set
of process flow semantics within a process and the communication between
independent processes. It is intended to support capture of sufficient detail to
allow it to be the source of an executable process description. Since
BPEL is currently considered the most important standard for execution
languages, a translation to BPEL is specified in the BPMN
standard.
Thanks,
Amit Gupta
----- Original Message -----
Sent: Wednesday, January 18, 2006 2:57
PM
Subject: Re:
[service-orientated-architecture] BPEL+
Amit Gupta ((FSI)) wrote:
Let me try and explain the difference between BPMN
and BPEL with an example.
If we have to represent a simple
banking transaction with BPMN, where we need to DEBIT $100 from 'Amit'
account and CREDIT the same to 'Steve' account.
In this case,
the BPMN based graphical semantics will simply state the steps as Start of
Process --> "Validate" Input ---> DEBIT Amit's account --> Apply
Transformation of data --> CREDIT Steve's account --> end of
Process.
The above BPMN semantics do not define the DATA
associated with each of the steps in above process flow. It simply shows a
SHEMATIC of the process flow.
However, when this BPMN compliant
flow is converted to BPEL, one can add specifics of the "format" of data
"going in" or "coming out" of each of the steps defined above (and details
of the actual transformation applied as well). Besides, each of the
"steps" can be represented as a WSDL invocation (which may or may not be
implemented using WS over SOAP)..
As such, I see BPMN as simply
the "visual face" of BPEL.
to which Steve Ross-Talbot
replied:
Interesting. I'm not at all sure that BPMN see it like this.
And
Steve is absolutely right (however the Fiorano software produced by Amit's
company operates). To see this, let's quote from the BPMN spec (v1.0 of
3 May 2004):
(p.43)
Modeler-defined Properties MAY be added to
a Process. These Properties are "local" to the Process. All Tasks,
Sub-Process objects, and Sub-Processes that are embedded SHALL have access
to these Properties. The fully delineated name of these properties are
"<process name>.<property name>" (e.g., "Add Customer.Customer
Name"). If a process is embedded within another Process, then the fully
delineated name SHALL also be preceded by the Parent Process name for as
many Parents there are until the top level Process.
(p.282)
B.11.7
Property
The following table displays the set of attributes of a
Property, which is used in the definition of attributes for a Process and
common activity attributes:
Name : String
Each Property has a Name
(e.g., name="Customer Name").
Type : String
Each Property has a
Type (e.g., type="String"). A Property may be of type Set, which allows
child Properties
[Type = "Set" only] Correlation (0-1) False :
Boolean
If the ConditionType attribute is set to _expression_, then the
ConditionExpression attribute MUST be defined. Otherwise, it is not
valid. This attribute is included for mapping to BPEL4WS. The Property
will map to a correlationSet and the child Properties will be properties of
that correlationSet. In other words, a BPMN process is intended to
contain enough information to specify all elements required to form a service
invocation. It was certainly never intended as merely the "visual face"
of anything, but as a complete graphical process description language.
You can use it with BPEL, yes (and the designers allowed for this specifically
in the case of Set properties), but you don't need anything underneath to
complete the process description.
Directly as a result of BPMN, BPEL
has become the Caliban of the IT world - the ill-formed and unlovable product
of an unholy alliance, destined for no good ... and the original dream of a
universal, pi-calculus-based BPM layer for enterprise IT now looks very
unlikely indeed ever to become reality. What we will get from the
BPM work to date is better graphical, deployment and analysis tools for
component technologies - not a bad thing, of course - and the focus of BPM
will inevitably move towards areas not covered by such component technologies
(i.e., human interaction).
--
All the best
Keith
http://keith.harrison-broninski.info
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