Invited presentation given by Niels Lohmann on June 27, 2006 in Turku, Finland as part of the Advanced Tutorial on Petri Net Modelling of Business Processes; satellite event of the PETRI NETS 2006/ACSD 2006 conferences.

1. Tools4BPEL Tutorial
Niels Lohmann
Humboldt-Universität zu Berlin
Department of Computer Science
nlohmann@informatik.hu-berlin.de

2. Overview
2

3. The tools
• BPEL2oWFN
translates a BPEL service into an oWFN
• Fiona
analyzes the interaction of an oWFN:
(1) checks controllability and
(2) computes the operating guideline of the net
• Tools4BPEL GUI
graphical user interface for BPEL2oWFN and Fiona
3

4. Download,
Setup and Install
4

5. Requirements
• to run:
– Windows, Linux, UNIX or Macintosh for BPEL2oWFN
and Fiona
– J2SE 5.0 (Java 1.5) for the GUI
• to compile:
– GNU Compiler Collection (gcc)
• to develop:
– GNU Autotools (automake, autoconf, …)
– GNU Compiler Tools (flex, bison, kimwitu++)
5

6. Download
• all tools are free and open source
• download them from the Tools4BPEL website
www.informatik.hu-berlin.de/top/tools4bpel
• the tools are also hosted at SourceForge.net
sourceforge.net/projects/tools4bpel
6

7. Set up BPEL2oWFN
• download the source tarball (“bpel2owfn-1.3.tar.gz”)
• open a shell and enter:
– gunzip bpel2owfn-1.3.tar.gz
– tar xf bpel2owfn-1.3.tar
– cd bpel2owfn-1.3
– ./configure
– make
• an executable file “bpel2owfn” is created in the
directory /bpel2owfn-1.3/src
7

8. Set up Fiona
• download the source tarball (“fiona-1.0.tar.gz”)
• open a shell and enter:
– gunzip fiona-1.0.tar.gz
– tar xf fiona-1.0.tar
– cd fiona-1.0
– ./configure
– make
• an executable file “fiona” is created in the
directory /fiona-1.0/src
8

9. Set up Tools4BPEL GUI
• download the jarfile (“tools4bpelgui-1.0.jar”)
• edit the config-file and point to the executables of
BPEL2oWFN and Fiona
• start the GUI with
java -jar tools4bpelgui-1.0.jar
9

10. BPEL2oWFN
10

11. Overview
• input:
– BPEL process (compliant to the
BPEL4WS 1.1 specification)
• output:
– oWFN
– Petri net (without interface places)
• additionally:
– control flow analysis
11

12. Translation
Translation can be adjusted to the analysis task:
– feature-complete
all aspects of BPEL are modelled
– abstraction from data
variables are not modelled
net size
– abstraction from fault management
fault and compensation handlers are not modelled
– abstraction from stop and termination management
only the communicational behaviour is modelled
12

13. Translation (cont.)
• Output file formats:
Petri net with
– oWFN in Fiona format interface places
– LoLA place/transition net
– Petri Net Markup Language (PNML) Petri net without
– Abstract Petri Net Notation (APNN) interface places
– Low-level PEP Notation
13

14. Translation (cont.)
• The translation is supported by:
– static analysis
– structural simplification rules
14

15. Control Flow Analysis
• detects design flaws:
– conflicting receive operations
– uninitialized variables
– cyclic links
(not presented here)
• more information on the website:
www.informatik.hu-berlin.de/top/tools4bpel/bpel2owfn
15

16. Fiona
16

17. Overview
• input:
– oWFN
• output:
– interaction graph
– operating guideline
17

18. Parameters
• set communication depth
• adjust maximal event occurrence
• usage of reduction rules for the IG
• more information on the website:
www.informatik.hu-berlin.de/top/tools4bpel/fiona
18

19. Example #1
The Online Shop
19

20. shop.bpel 20

21. Description
When the online shop receives the login information from a
customer, its business strategy distinguishes between already
known customers and new customers. In case of a known
customer the left branch is executed: first the shop expects an
order, and then it sends the invoice to the customer. In case of a
new customer (right branch) the shop initiates two tasks
concurrently: in the first task (Sequence1) the shop first receives
the order and then confirms it. In the second task (Sequence2)
the shop receives the terms of payment before it sends an invoice
to the customer. In either case the shop finally sends the delivery
information to the customer. The customer may send an abort
message at any time. This is modelled by an event handler that
receives the abort message and then terminates the whole
process. 21

22. Analysis tasks
• Does there exist a partner that can use the online
shop “properly”, i.e. login, order and eventually
receive a delivery information?
• If there exists more than one partner of the online
shop, can we characterize all of them?
22

23. Todo
1. Translate the BPEL process to an oWFN
(prerequisite for further analysis)
2. Check for controllability and calculate the IG
(analysis: existence of a partner)
3. Calculate the operating guideline
(analysis: characterize all partners)
23

24. 1. Translation
We use BPEL2oWFN to generate an oWFN:
the modelling of
./bpel2owfn standard faults, data
or variables is not
--input=shop.bpel
necessary for this
--mode=petrinet analysis task
--format=owfn
--parameter=novariables
--parameter=nostandardfaults
--parameter=simplify structurally simplify
--output the resulting net
24

25. 1. Translation (cont.)
• BPEL2oWFN creates a
file “shop.owfn”:
– 70 places (4 input, 3 output)
– 75 transitions
– 233 arcs
• Due the <terminate/>
activity, each BPEL activity
has a stop pattern.
25

26. 2. Controllability
We use Fiona to calculate the interaction graph:
./fiona
--net=shop.owfn
--graphtype=IG
26

27. 2. Controllability (cont.)
• Fiona creates two files:
– “shop.owfn.IG.out”
– “shop.owfn.IG.png”
• The interaction graph has
a blue subgraph:
) The online shop is controllable!
27

28. 2. Controllability (cont.)
The controller found reflects the intended behaviour
of a customer. First he sends a login, followed by an
order. Then he must be able to either receive an
invoice (in case he is known to the shop) or to receive
the confirmation (in case he is a new customer). If he
actually has received the confirmation, he must send a
terms of payment message. After that he will receive
the invoice. In either case he finally receives the
delivery information. At any time he may abort.
28

29. 3. Operating Guideline
We use Fiona to calculate the operating guideline:
./fiona
--net=shop.owfn
--graphtype=OG
29

30. 3. Operating Guideline (cont.)
• Fiona again creates two files:
– “shop.owfn.OG.out”
– “shop.owfn.OG.png”
• The operating guidelines contains
more interleavings of sending or
receiving messages. For instance,
a customer may reverse the order
of sending the login and the
order message.
30

31. Example#2
The new Online Shop
31

32. newshop.bpel 32

33. Description
The shop now modifies its business strategy: every
known customer that orders something can choose a
gift. The changes only affect the left branch of the
switch. The shop initiates two tasks concurrently now:
in the first task (Sequence1) the shop first receives the
order and then confirms it. In the second task
(Sequence2) the shop receives which gift is chosen
before it sends the invoice to the customer.
33

34. Analysis tasks
• Does this change have an impact on the partners?
34

35. Todo
1. Translate the BPEL process to an oWFN
(prerequisite for further analysis)
2. Check for controllability and calculate the IG
(analysis: existence of a partner)
3. Calculate the operating guideline
(analysis: characterize all partners)
4. Compare it to the operating guideline of the first
online shop 35

36. 1. Translation
• Using the same parameters
as before, BPEL2oWFN
generates an oWFN:
– 83 places (4 input, 3 output)
– 90 transitions
– 279 arcs
36

37. 2. Controllability
• Using the same parameters as
before, Fiona calculates an
interaction graph with a nonempty
blue subgraph:
The new shop is still controllable!
• The controller in the IG represents a
customer who sends an abort
message during the interaction.
37

38. 3. Operating Guidelines
• Using the same parameters as
before, Fiona calculates the
operating guideline of the new
shop.
38

39. 4. Comparison
A closer look at the OG reveals that actually every
customer of the modified shop must eventually send
an abort message. This surely means that the process
is controllable. However, the way this is done is
obviously a not intended one. There is no way that a
customer can get what he has ordered from the
process.
39

40. 4. Comparison (cont.)
We can see that the shop does not communicate its inner
decision about which branch (known customer, new customer) is
chosen. In the original online shop the controller must send an
order, but receives either an invoice or a confirmation w.r.t. which
branch the shop has chosen before. That way the controller knows
what branch the shop is actually in and hence knows how to
continue. In contrast, in the modified shop the controller must
send an order and receives undistinguishable confirmation
messages in either case. The modified shop expects a choice of a
gift in case it decided for the known customer branch. In the other
case it expects the terms of payment. The controller, however,
does not know about the decision of the shop. However, sending
an abort is always correct.
40

41. Example #3
Coffee Vending
Machine
41

42. coffee.bpel
42

43. Description
The coffee vending has a button for coffee and one for
tea, and a money slot. After money is inserted and a
button is pressed, the beverage (coffee or tea) is
returned.
43

44. Analysis Task
• Are these three customers partners of the coffee
vending machine?
customer1.bpel customer2.bpel customer3.bpel
44

45. Todo
1. Translate the vending machine service to an
oWFN.
2. For each customer service:
a) Translate the service to an oWFN.
b) Compose this oWFN with the oWFN of the
service.
c) Test: Is the composed service weak
terminating?
45

46. Translation and Composition
BPEL2oWFN can perform step 1, 2a and 2b:
compose the input
services and create
./bpel2owfn a CTL formula to
-- mode=consistency check
-- input=coffee.bpel
-- input=customer1.bpel
-- format=lola use patterns that
-- parameter=communicationonly only model the
-- parameter=simplify communicational
-- output behaviour
46

47. Translation and Composition (cont.)
• BPEL2oWFN creates two files for the explicit model
checker LoLA:
– coffee_customer1.lola
the composed net in LoLA format
– coffee_customer1.task
a CTL formula stating that it is always possible to
reach the final marking of the composed net
(AG EF finalmarking)
47

48. Test on weak termination
• We use the LoLA to check the CTL formula:
./lola coffee_customer1.lola -a
• LoLA verifies the formula: the final state of the
composed service can be reached from any
reachable marking
48

49. Results
• The composition weakly terminates.
) The first customer is a partner of the coffee
vending machine (and vice versa).
• Using the same parameters, we find that the
second consumer is also a partner of the coffee
vending machine (and vice versa).
49

50. Results (cont.)
• The composition of the coffee vending machine
service and the third consumer does not weakly
terminate:
– LoLA finds a counter example path (the
composition deadlocks after the coffee button is
pressed).
– This path can be used to fix the BPEL process of
this customer (an automatic re-translation is
subject of current work).
50

51. Conclusion
and References
51

52. Conclusion
The presented tools can:
• generate a formal model of a BPEL process
(translate a BPEL process to an oWFN or a Petri net
without interface),
• generate a partner of a service, if there is one (check
an oWFN for controllability),
• characterize all partners of a service (calculate the
operating guideline of an oWFN),
• check if two services are partners, i.e. they are
consistent (check if the composition is weakly
terminating).
52

53. References
• These slides together with all examples can be
downloaded at:
www.informatik.hu-berlin.de/top/tools4bpel/tools/tutorial
• For more information on the tool chain, see:
Niels Lohmann, Peter Massuthe, Christian Stahl, and
Daniela Weinberg. Analyzing Interacting BPEL Processes.
BPM 2006, Lecture Notes in Computer Science (to appear),
2006. Springer-Verlag.
53

54. References (cont.)
• For more information on LoLA, see:
Karsten Schmidt. LoLA: A Low Level Analyser. In Mogens
Nielsen and Dan Simpson, editors, ICATPN 2000, volume
1825 of Lecture Notes in Computer Science, pages 465-474,
June 2000. Springer-Verlag.
• LoLA can be downloaded at:
www.informatik.hu-berlin.de/top/lola
54

55. Tools4BPEL Tutorial
Niels Lohmann
Humboldt-Universität zu Berlin
Department of Computer Science
nlohmann@informatik.hu-berlin.de