=Paper=
{{Paper
|id=Vol-272/paper-3
|storemode=property
|title=The PiVizTool: Simulating Choreographies with Dynamic Binding
|pdfUrl=https://ceur-ws.org/Vol-272/BPM07DemoProgramPaper2.pdf
|volume=Vol-272
|dblpUrl=https://dblp.org/rec/conf/bpm/BogPW07
}}
==The PiVizTool: Simulating Choreographies with Dynamic Binding==
https://ceur-ws.org/Vol-272/BPM07DemoProgramPaper2.pdf
The PiVizTool:
Simulating Choreographies with Dynamic
Binding
Anja Bog, Frank Puhlmann, and Mathias Weske
Business Process Technology Group
Hasso Plattner Institut for IT Systems Engineering
University of Potsdam
D-14482 Potsdam, Germany
{anja.bog,frank.puhlmann,mathias.weske}@hpi.uni-potsdam.de
Abstract. This paper presents a tool, the PiVizTool, for the interac-
tive simulation of choreographies. Different participant instances can
be added, deleted, and dynamically bound during the simulation. The
PiVizTool uses the π-calculus as the formal foundation for representing
dynamic binding. It provides an interactive graphical representation of
complex choreographies that can be simulated according to different use
cases.
1 Introduction
Nowadays, service-oriented architectures (SOA) are a common realization strat-
egy for business process management (BPM). In a SOA, business processes are
represented as services with internal and communication actions following a busi-
ness logic. Multiple of these services work together in a choreography to provide a
result. A core feature of service-oriented architectures is dynamic binding, which
allows services to be bound at runtime.
Consider for instance figure 1, that shows the design-time view of a choreog-
raphy in BPMN [1]. The initial participant is a customer, shown in the upper
part. The customer places an order, a delivery address, and an invoice address
at a reseller. The reseller has a number of manufacturers and payment organi-
zations that handle each request. While at design-time the static interfaces of
the manufacturer and the payment organization are given, different implementa-
tions might be bound during runtime. All of them directly bind to the addresses
initially given by the customer to the reseller for providing their services.
2 The PiVizTool
The PiVizTool1 provides an interactive environment for choreographies, where
different participant instances can be added (imported) and selected during the
1
The PiVizTool is available at http://bpt.hpi.uni-potsdam.de/twiki/bin/view/
Piworkflow/Simulator.
2 Anja Bog, Frank Puhlmann, and Mathias Weske
Receive
Invoice
CUSTOMER
Order
Receive
Product
PAYMENT ORG.
Send
Invoice
RESELLER
Place Place
Invoice Product
Request Request
MANUFACTURER
Send
Product
Fig. 1. A choreography in BPMN notation.
runtime of the simulation. The tool is grounded in the π-calculus [2], where the
choreographies are formally defined according to [3,4]. The major difference be-
tween the π-calculus and other formalizations—such as Petri nets—is given by
the inherent support of link passing mobility. Channels between business part-
ners are denoted as links, where the links could be passed via other links (chan-
nels) to possible interaction partners. The technical foundation allows the direct
representation of common patterns like asynchronous callback (problem here:
correlate the matching process instances) as well as dynamic routing (problem:
how to invoke interaction partners initially unknown).
An initial view of the given example in the PiVizTool is shown in figure 2.
The main part shows the current state of the system representing the investi-
gated choreography. Each participant of the BPMN diagram is depicted as a
rectangle, representing an instance. All BPMN flow objects are shown as circles.
The dependencies between the flow objects (sequence flows) are shown as lines
with a dotted end marking the target. The message flows, however, have been
restricted to the current knowledge of the system. We can see a link between the
instances of the customer and the reseller, as well as two links from the reseller
instance to a certain instance of the payment organization. There is no link back
to the customer at this point in (simulation) time. The left hand side of the tool
shows all dynamically created channels and links that are currently contained in
the system. We can see invAddr#21 and itemAddr#20 representing the return
channels of the invoice and the ordered items for the customer instance. The
static channels, like order (shown in the main view between the customer and
the reseller) are not contained in the list. Above the graphical view, the original
as well as the current π-calculus representation of the system can be selected for
viewing.
The PiVizTool: Simulating Choreographies with Dynamic Binding 3
Fig. 2. The initial state of the example from figure 1 in the PiVizTool.
The user can execute an arbitrary action of the simulation—that is currently
possible—by using the ExecStep button at the top of the interface. He can also
click on an active element of the graphical representation to execute it. Active
elements are either activities (depicted as circles filled with gray) or channels
(depicted with bold, black lines). In the case of the example, the only action
possible is the CStart activity that represents the start event of the customer.
As stated, it can be triggered by clicking on it.
If an action is executed, the underlying π-calculus terms are evolved and a
new graphical view of the system is created. The layout of the new view might
be changed, because the visualization algorithm always calculates a view, where
the interconnections between the nodes are minimized. Furthermore, new actions
are made available according to the current state of the simulation.
After several actions, the state of the system has changed as shown in figure 3.
The customer instance has placed the order, the delivery address, and the invoice
address at the reseller. At this point in time, no channel between the instances
of the customer and the reseller is existing. What has been added, however,
is another instance of the payment organization via the execution menu of
the PiVizTool that allows the addition of arbitrary participant instances during
runtime (while not shown, it is even possible to instantiate completely different
participants). Both instances of the payment organization can be reached via
4 Anja Bog, Frank Puhlmann, and Mathias Weske
Fig. 3. The state of the example where the customer has placed his order and a
second instance of the payment organization has been created.
the same channel, payChan. In the course of the simulation, the user can select
the one he wants to activate.
3 Conclusion
This paper gave a short introduction to the PiVizTool that is able to simulate
choreographies with dynamic binding based on the π-calculus. Currently, the
input is restricted to plain π-calculus files, but we’re working on enhancing the
tool supported mapping of BPMN to pi-calculus based on our tool chain intro-
duced in [5]. An extended description as well as the theoretical background is
described in [6].
References
1. BPMI.org: Business Process Modeling Notation. 1.0 edn. (2004)
2. Milner, R., Parrow, J., Walker, D.: A Calculus of Mobile Processes, Part I/II.
Information and Computation 100 (1992) 1–77
3. Puhlmann, F., Weske, M.: Using the Pi-Calculus for Formalizing Workflow Patterns.
In: Business Process Management, volume 3649 of LNCS, Berlin, Springer Verlag
(2005) 153–168
4. Overdick, H., Puhlmann, F., Weske, M.: Towards a Formal Model for Agile Ser-
vice Discovery and Integration. In: Proceedings of the International Workshop on
Dynamic Web Processes (DWP 2005). IBM technical report RC23822, Amsterdam
(2005)
5. Puhlmann, F.: A Tool Chain for Lazy Soundness. In: Demo Session of the 4th
International Conference on Business Process Management, CEUR Workshop Pro-
ceedings. Volume 203., Vienna (2006) 9–16
6. Bog, A.: A Visual Environment for the Simulation of Business Processes based
on the Pi-Calculus. Master’s thesis, Hasso-Plattner-Institute, Potsdam, Germany
(2006)