Tools4BPEL Tutorial

Niels Lohmann

Humboldt-Universität zu Berlin Department of Computer Science

nlohmann@informatik.hu-berlin.de

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Overview

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The tools

• BPEL2oWFNtranslates a BPEL service into an oWFN

• Fionaanalyzes the interaction of an oWFN:(1) checks controllability and(2) computes the operating guideline of the net

• Tools4BPEL GUIgraphical user interface for BPEL2oWFN and Fiona

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Download,Setup and Install

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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++)

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Download

• all tools are free and open source

• download them from the Tools4BPEL websitewww.informatik.hu-berlin.de/top/tools4bpel

• the tools are also hosted at SourceForge.netsourceforge.net/projects/tools4bpel

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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

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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

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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 withjava -jar tools4bpelgui-1.0.jar

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BPEL2oWFN

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Overview

• input:– BPEL process (compliant to the

BPEL4WS 1.1 specification)

• output:– oWFN– Petri net (without interface places)

• additionally:– control flow analysis

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Translation

Translation can be adjusted to the analysis task:– feature-complete

all aspects of BPEL are modelled

– abstraction from datavariables are not modelled

– abstraction from fault managementfault and compensation handlers are not modelled

– abstraction from stop and termination managementonly the communicational behaviour is modelled

net s

ize

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Translation (cont.)

• Output file formats:– oWFN in Fiona format

– LoLA place/transition net– Petri Net Markup Language (PNML)– Abstract Petri Net Notation (APNN)– Low-level PEP Notation

Petri net withoutinterface places

Petri net withinterface places

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Translation (cont.)

• The translation is supported by:– static analysis– structural simplification rules

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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

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Fiona

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Overview

• input:– oWFN

• output:– interaction graph– operating guideline

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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

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Example #1The Online Shop

20shop.bpel

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DescriptionWhen 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.

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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?

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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)

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1. Translation

We use BPEL2oWFN to generate an oWFN:

./bpel2owfn--input=shop.bpel--mode=petrinet--format=owfn--parameter=novariables--parameter=nostandardfaults--parameter=simplify--output

the modelling of standard faults, data or variables is not necessary for this analysis task

structurally simplifythe resulting net

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1. Translation (cont.)

• BPEL2oWFN creates afile “shop.owfn”:– 70 places (4 input, 3 output)– 75 transitions– 233 arcs

• Due the <terminate/> activity, each BPEL activity has a stop pattern.

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2. Controllability

We use Fiona to calculate the interaction graph:

./fiona--net=shop.owfn--graphtype=IG

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2. Controllability (cont.)

• Fiona creates two files:– “shop.owfn.IG.out”– “shop.owfn.IG.png”

• The interaction graph hasa blue subgraph:

) The online shop is controllable!

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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.

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3. Operating Guideline

We use Fiona to calculate the operating guideline:

./fiona--net=shop.owfn--graphtype=OG

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3. Operating Guideline (cont.)

• Fiona again creates two files:– “shop.owfn.OG.out”– “shop.owfn.OG.png”

• The operating guidelines containsmore interleavings of sending orreceiving messages. For instance,a customer may reverse the orderof sending the login and theorder message.

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Example #2The new Online Shop

32newshop.bpel

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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.

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Analysis tasks

• Does this change have an impact on the partners?

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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

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1. Translation

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

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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.

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3. Operating Guidelines

• Using the same parameters as before, Fiona calculates theoperating guideline of the newshop.

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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.

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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.

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Example #3Coffee Vending

Machine

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coffee.bpel

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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.

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Analysis Task

• Are these three customers partners of the coffee vending machine?

customer1.bpel customer3.bpelcustomer2.bpel

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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?

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Translation and Composition

BPEL2oWFN can perform step 1, 2a and 2b:

./bpel2owfn-- mode=consistency-- input=coffee.bpel-- input=customer1.bpel-- format=lola-- parameter=communicationonly-- parameter=simplify-- output

compose the inputservices and createa CTL formula tocheck

use patterns thatonly model thecommunicationalbehaviour

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Translation and Composition (cont.)

• BPEL2oWFN creates two files for the explicit model checker LoLA:

– coffee_customer1.lolathe composed net in LoLA format

– coffee_customer1.taska CTL formula stating that it is always possible to reach the final marking of the composed net(AG EF finalmarking)

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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

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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).

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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).

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Conclusionand References

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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).

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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.

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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

Tools4BPEL Tutorial

Niels Lohmann

Humboldt-Universität zu Berlin Department of Computer Science

nlohmann@informatik.hu-berlin.de