An Introduction to BPEL standard and its extentions - SoberIT

An Introduction to BPEL standard and its extentionsYanbo WuT-86.5161 Special Course in Information Systems integration,HUT, FinlandAbstract. BPEL (also known as WS-BPEL) is an XML-based language that allows business todescribe inter or intra enterprise business processes that are connected via Web services. Due tothe limitation of traditional methods for business integration and process automation, BPELcame to the picture and highly promoted by companies such as IBM and Oracle. Specification ofWS-BPEL 2.0 has been approved as OASIS Standard. In practice, BPEL is typically used whenapprove loan request and make travel reservation. To support a broaden range of scenariosinvolving people and sub-process within business processes, two BPEL extensions,BPEL4People and BPEL-SPE, are developed. Both extensionts are still in their early stages.Due to the increased importance of business integation, EU SUPER project started in 2006aiming to achieve better cooperation between IT and business.

1. INTRODUCTION1.1 BackgroundWeb Service Orchestration (WSO) provides the ability to integrate and assemble individual Web servicesinto standards-based business processes. It is a bridge to connect an enterprise’s Service OrientedArchitecture and a critical layer in the web services technology. To facilitate WSO, the Business ProcessExecution Language (BPEL) was created to standardize integration logic and process automation betweenweb services. Combination of business process execution standards and Web services promises todramatically reduce costs and provide broader interoperability and reusability benefits.BPEL or WS-BPEL permits orchestration of web services. While the obvious business activity of ahuman interaction and sub-process are not covered by BPEL. To support a broaden range of scenarios,several BPEL extensions were proposed, and in this paper BPEL4People and BPEL-SPE are beingdiscussed.1.2 Objective to review current BPEL and the proposed extensions General picture of BPEL, its extension BPEL4People and BPEL-SPE Specification of above standard Study the result of EU SUPER project1.3 Scope of this paper Basic concept of latest on BPEL related technology Simple case analysis1.4 Research problemIn this paper, I study the current BPEL standard and what can be achieved with it, as well as the proposedextensions and their improvement over the existing BPEL standards.1.5 MethodologyLiterature review is the main methodology used in this project. The sources for literature are from Internet,academic journals, books and thesis database.1.6 Structure of report1. Introduction of project2. BPEL and its application in business3. BPEL4People4. BPEL-SPE5. EU Super project6. BPEL case study7. Conclusion8. Reference

2. BPEL AND ITS APPLICATION IN BUSINESSWeb service is thought to be the next “great thing” in the area of e-commerce and system integration.However, Web service is merely “great technology” without a way for business to use it, unless there is acommon standard to orchestrate multiple services into business and audit/manage the results. BPEL actsas “glue” to connect Web services and cohesive business solution, enables the orchestration of tasks inweb-based services.2.1 What is BPEL?BPEL (Business Process Execution Language), also known as BPEL4WS or WSBPEL, is an XML-basedlanguage that allows business to describe inter or intra enterprise business processes that are connectedvia Web services. BPEL is the convergence of language features of IBM’s WebService Flow Language(WSFL) and Microsoft’s XLANG [1]. As an XML-based language, BPEL describes the logic tocoordinate Web services in a process flow. The XML grammar can be interpreted and executed by aBPEL orchestration engine, which controls all activities in the process [1].Many companies including IBM, Oracle as well as open source organizations have released BPELimplementations in their platforms and tools. The available BPEL engines includes Oracle BPEL ProcessManager, IBM BPWS4J, Apache ODE, ActiveBPEL, Twister [2]2.2 Why BPEL is needed?Traditional methods for business integration and process automation usually involve logic inside ofapplications designed to meet a specific business need such as ERP, supply chain, CRM. Thedevelopment, testing and making the change of such applications can be quite costly and complicated [1-4]. To solve the problem, proprietary Enterprise Application Integration (EAI) and Business ProcessManagement (BPM) emerged to raise integration and process automation into a new level of softwaretools [5]. But proprietary EAI and BPM are too expensive [5].XML-based Web services came into picture as a solution. However, Web services do not fulfill the needto integrate and coordinate business processes themselves. This is where BPEL appeared (Figure 2.1) [1,5].Adoption of Web services and BPEL enhances productivity, reduces operating costs and betters servicethrough process automation.

Traditional business integration and process automation methodsExpensive to make changesWeb servicesWProprietary EAI and BPMToo expensiveImplementation of Internet transportprotocols (HTTP, SMTP)Data model (XML)Message exchanged (SOAP)Description of service operations andspecifications (WSDL)Publishing and discovery of services(UDDI)Unable to fill the need themselvesBPELFigure 2.1: Development of process integration and process automation [1, 5]2.3 DevelopmentBPEL 1.0 was initially developed by Microsoft, IBM and BEA as BPEL4WS in August 2002. In April2003, BPEL 1.1 was first submitted to OASIS to obtain broader acceptance and open standardization [3,6]. The OASIS WS-BPEL technical committee voted on 14 September 2004 to name their specificationWS-BPEL 2.0, and approved it as OASIS standard on 12 April 2007 [2, 7].2.4 What can BPEL do?BPEL makes it possible to keep internal business processes separated from external enterprise processes.Hence, changing of internal processes will not affect data exchange between enterprises [3].BPEL provides enterprise with a standard for business orchestration and execution. It specifies how tosend/receive XML messages, exchange message with partners, implement parallel or sequential process,manipulate data between partner interactions, define parallel/sequential execution, etc [6].By using BPEL it Makes integration with business partners easier and more effective Stimulates enterprises to further define their business processes, Leads to further optimizing the business process

3. BPEL4PEOPLE3.1 Limitation of BPEL4WS and demand for BPEL4PeopleBPEL permits orchestration of web services, while the obvious business activity of a human interactionwithin a process is not covered by BPEL [8], and this means that vendors will most probably create theirown proprietary extention to BPEL, and this will result worse interoperability between products, thereforeit makes sense to standardize this part of the process too. However the activities that make up generalbusiness processes are broader than this, because people often participate in the execution of businessprocesses. To support a broaden range of scenarios involving people within business processes, a BPELextension is required [9, 10]. An additional group of syntax and semantics which focus on the descriptionhas to be added to BPEL.3.2 Development of BPEL4PeopleIBM and SAP recognized the importance of extending BPEL for people and jointly published a whitepaper in July 2005 [13, 14, 15, 19]. It addresses various BPEL4People requirements and scenarios.In June 2007, Active Endpoints, Adobe, BEA, IBM, Oracle and SAP published the BPEL4People andWS-HumanTask specifications, which define an approach for integrating human interactions using WS-BPEL 2.0 [9-12]. The authors of BPEL4People plan to submit the specifications to OASIS (Organizationfor the Advancement of Structured Information Standards) in the near future [12].3.3 BPEL4People specificationA BPEL language contains features needed to describe complex control flows. Since human interactionsare usually involved in business process, BPEL process should define people as another type ofparticipants.BPEL4People is now comprised of two specifications [12]: WS-BPEL Extension for People (BPEL4People) Version 1.0, which features lay on top of WS-BPELto describe human tasks as activities that may be incorporated as first-class components in WS-BPEL process definitions. Web Services Human Task (WS-HumanTask) Version 1.0, which introduces stand-alone human tasks.Web Services Human Task may be utilized by Web services-based applications beyond WS-BPELprocesses.BPEL specification focus on the business activities which interact with Web services. BPEL4Peoplespecification extends BPEL elements and enables the modeling of human interaction patterns [12].Complete specifications of BPEL4People 1.0 and WS-HumanTask 1.0 can be found at [13, 14].3.3.1 People integrationTo achieve best possible interact between people and process, it is essential to understand people roles inthe process and how process identifies the people to interact with.

3.3.1.1 Human rolesIn BPEL4People process, four generic human roles are defined: process initiator, process stakeholders,potential owner and business administrators [13, 15].Process initiator is the person who triggers the process instance. The initiator can be either determined bythe process automatically or specially assigned.Process stakeholder is the person who can influence the progress of a process instance. Their responsiblecan be adding attachment, forward task or follow the process progress. If no process stakeholders arespecified, the process initiator becomes the process stakeholder. The process stakeholder is onlyassociated with a process instance.Potential owner is the person who is assigned to claim and complete the activity.Business administrator is the person who is allowed to perform administrative actions on the businessprocess. If no business administrators are specified, the process stakeholders become the businessadministrators. Unlike process stakeholder, a business administrator has an interest in all processinstances and not just one.3.3.1.2 People linkPeople links are used to bind a group of people to a business process, they are similar to partner linkswhich are used to bind Web services to processes. People links are usually associated with generic humanroles.Using human roles and people link, a people activity is defined (Section 3.3.2.1).3.3.2 ScenariosPeople interaction can be as simple as manual approval, such as giving approval/rejection to loan request.People interaction can be more complex involving data, such as feeding customer feedback to the process.The scope of BPEL4People is described in five scenarios [15].3.3.2.1 People activityThe new BPEL activity – people activity is not performed by any software, it is the task assigned to a userand it requires action be performed by that user [15]. The actor of a people activity is determined by apeople link. In PBEL4People, BPEL engine does not invoke Web services, instead it creates anddistribute a task to certain user. And user needs to carry out specific action on task. Like BPEL activity,people activity has name and input/output variable, it allows the specification of deadlines. Moreover,people activity can set a priority, which prioritizes the work people work on [15].3.3.2.2 Initiating processWhen a group of people involved in a business process, it is necessary to appoint people who initiate abusiness process.

3.3.2.3 Managing processIn a long-running business process, continuous human involvement may be expected. Let’s use an onlinevoting system as example. The online voting site could be jammed due to excess data flow. In order tokeep the process running smoothly, people with adequate business knowledge should be assigned asbusiness administrators, and shut down the voting system temporarily, when the excess data flow reachescertain limits. These business administrators (humans) play crucial role to ensure the running running andbest possible outcome of the process[15].3.3.2.4 Human and automatic services transitionThis scenario defines that two-way transition between human and automatic services must be nondisruptive.3.3.2.5 Advanced people interactionAbove four scenarios are simple task and execution actions. In many cases people interact with process ina more complex pattern, which requires BPEL4People [15].4-Eyes Principle takes place when decision needs to be made independently by two or more users. In theextreme case, users are not allowed to know who else is involved in the decision making.Escalation is used if a task does not progress as expected or it does not meet its deadline. If it occurs, anotification is sent to escalation recipients. Then they will decide further actions to get the process backon track.Nominations, just as its name implies, it is used to nominate user for certain task.Chained execution referes to scenario where a sequence of actions is taken by a same person. In thiswizard-style interaction, the person running the process is also the process initiator.3.3.3 TaskThe work people perform is defined as task, which has following properties [15]: Multilingual description Priority Expected data Deadline User interfaceWhen task is integrated with process, two patterns are formed: inline tasks or standalone tasks [15].

BPEL ProcessBPEL ProcessBPEL ProcessBPEL ProcessPeopleActivityPeopleActivityPeopleActivityPeopleActivityInlineHumantaskInlineHuman taskStandaloneHuman taskCallableWSDLInterfaceHTProtocolInterfaceStandalone HumantaskFigure 3.1: Interaction patterns between process and task [15]In Pattern 1, the task is specified inline within a People activity. In Pattern 2, the task is specified inlinewithin the BPEL process. In both patterns, the task automatically shares process context and data.In Pattern 3, the task is defined externally to the process without a specific interface, In that wayapplication vendors can expose their functionality as tasks which can be called from BPEL processengines.Pattern 4 is like 3 except that the task interface is specified using a callable WSDL, which is invokedusing Web services. Moreover, WS-HumanTask is used for communication between process and task.4. WS-BPEL 2.0 EXTENSIONS FOR SUB-PROCESSES – BPEL-SPE4.1 Demand for BPEL -SPEBesides excluding people action, BPEL does not support the explicit definition of business “fragments”that can be invoked from another (or the same) business process either [16]. In both the BPEL4WS 1.1and the WS-BPEL 2.0 specifications,, the only way to simulate this behavior is to define a completebusiness process as an independent service and invoke it via invoke activity. However, sub-process iscompletely hidden from its parent process, namely it does not have lifecycle coordination with its parentprocess.4.2 Development of BPEL-SPEIn September 2005, IBM and SAP published a white paper called Extensions for Sub-Processes (BPEL-SPE). The paper calls for the explicit definition of sub-processes, allowing for the reuse of the subprocess,tight coupling of the sub-process's lifecycle with its parent process, and the ability of the subprocessto access its parent processes data [16]. The language specification defining the precise syntaxand semantics will be published in the future.

4.3 Sub-processAs a fragment of BPEL code a sub-process should be reused within a process or across multiple processes[15]. It can be defined as standalone sub-process and inline sub-process (Table 4.1).Table 4.1: Sub-processes typesStandalone Sub-processDefinition Defined within anotherBPEL processReuseReused only within thatprocessAccess to variables Can access only globalprocess variablesProperties Have its own variables,partner links, receiveactivityInline Sub-processDefined as a BPEL processReused across other BPELprocessCan access no variables fromother processesDoes not have its ownvariables, partner links,receive activity4.4 Invoke activityTwo invoking mechanisms between parent process and sub-process are supported by BPEL-SPE Via a reply activity Via a one-way invoke activityParentProcessWSDL request responseSub-ProcessFigure 4.1: Receive-reply invocation mechanisms [15]Sub-process receives the input message via its receive activity and responds the message via its replyactivity.

ParentProcessCall...partnerLink=”PL”requestOperation= “op1”responseOperation= “op2”Op1Sub-ProcessOp2PT2PLPT1Figure 4.2: Receive-invoke invocation mechanisms [15]The parent process uses call activity to call sub-process. The call activity specifies the port type which isused to send the input message to sub-process and port type which contains the operation to be used bysub-process to return a message. Several parent processes can call same sub-process, which means subprocessneeds to return message to different endpoints. Therefore it is important that those endpoints inparent processes are recognizable by the process engine hosting sub-process, so that response messagecan be sent back successfully [15].4.5 Coordination scenariosThere are seven coordination scenarios between a parent process and a sub-process (Figure 4.3)[15]Parent processRequest operationResponse operationCloseCloseSub-processFigure 4.3a Invocation of sub-process without compensationSub-process is invoked and message is returned. After parent process is completed, sub-process is closed.

Parent processRequest operationResponse operationCompensateCompensateSub-processFigure 4.3b: Invocation of sub-process with compensationSub process is invoked and message is returned. Compensation occurs and it passes to sub-process.Parent processSub-processRequest operationResponse operation – fault dataFigure 4.3c: Invocation of sub-process with application faultSub process is invoked, but it does not send result back to parent process, instead it sends fault data andcloses.Parent processSub-processRequest operationAbnormalSubprocessTerminationFigure 4.3d: Invocation of sub-process with application faultSub process is invoked, but it does not send message back to parent process as it should be.AbnormalSubprocessTermination is sent to parent process.

Parent processRequest operationTerminateTerminateSub-processFigure 4.3e: Invocation of sub-process with terminationSub process is invoked. Parent process is terminated and termination is passed to sub-process. Finally,termination completion is sent back to parent process.Parent processSub-processRequest operationSubprocessExitedFigure 4.3f: Invocation of sub-process with exit (parent process to sub-process)Sub process is invoked. Parent process encounters an exit activity and exit is passed to sub-process.SubprocessExited is sent to parent process.Parent processRequest operationSub-processExitedFigure 4.3g: Invocation of sub-process with exit (sub-process to parent process)Sub process is invoked and it encounters an exit activity. The exit is passed to parent process. Sub-processexits in turn.4.6 Future actionThe white paper only recognizes the problem of process reused in BPEL, describes different invocationscenarios and coordination mechanisms between parent process and sub/process. However, no consensuson how the problem should be resolved. No other official paper had been released than BPEL-SPE whitepaper. Detailed BPEL-SPE language specification (syntax and semantics) is still under construction

5. EU PROJECT SUPERIt happens quite often that IT staff is needed to solve business problems. The situation is quitetroublesome, which is both resource and time consuming. The needs for better alignment between IT andbusiness are getting stronger.Starting on 1st April 2006 Semantics Utilised for Process Management within and between EnterpRisesproject, also called SUPER project, is an integrated project funded by European Sixth FrameworkProgram. It has 3-year duration. 19 educational and industrial partners take part in the project [17, 18].Overall budget of the project is 16.4 M Euro, of which 11 M Euro is from funding [18].SUPER project intends to raise business process management (BPM) from the IT level to the businesslevel. It will enable business to use information technology more efficiently and to make cooperationbetween IT and business better. To achieve this objective, the project aims at adopting Semantic WebServices technology to make companies more adaptive.In 2006 the BPM domain was framed. In 2007 SUPER focused on the tools of semantic technologies inthe business process domain [19].6. CASE STUDY – EXAMPLE OF THE USE OF BPELBPEL4People and BPEL-SPE are still on their very early stage, no specification has been approved asOASIS standard. Since, their language specifications and structures are based on BPEL, I will take asimple BPELWS example to illustrate how BPEL related application is used in practice [20].6.1 Case scenariosIn the case, a loan procurement application is implemented by a bank called Superloan. An applicantsends a loan request, then the request is handled by Superloan, finally the decision is sent back toapplicant stating whether the loan is permitted or not.6.2 Setting up the systemIn BPEL receive activity, invoke activity and reply activity are used for getting a message, invoking theWeb service and returning results to customer respectively [20, 21]. Since above three actions are takenon after the other, it needs sequence activity to ensure they occur in right order. That will means firstreceive to get the message, then invoke to call Superloan approval process, and finally reply to senddecision to applicant (Figure 6.1).

ApplicantSuperloanBPELWS loan approval processLoan approverWeb servieFigure 6.1: Loan approval process6.3 Service descriptionIn order to exchange the message and invoke the Web service WSDL, description of services involved inthe BPEL process must be written beforehand. In this case, loan definitions, loan approval service andloan approval process.6.4 Creating processBPEL process likes a box where relationship to external partners, handlers for various purpose andactivities to be executed can be declared [21]. A BPEL process always begins with process.1Each service interaction in BPEL process is modeled as a partnerLink. For one partner, there can be aseveral partner links. In order to specify the role and the type of a partner, PartnerLinkType and a rolename are used [21]. In the case the partners are the applicant and loan approver. MyRole means the roleprocess plays, while partnerRole means the role that partner plays.1

Message is stored in containers to where BPEL can have access [20].6.5 Receive, invoke and reply activityReceive, reply and invoke are the activities for exchanging messages with external partners.Receive is used for receiving messages from an external partner. It always specifies the partnerLink andan operation that can be invoked. A process can be initiated by setting createInstance to yes in a receiveactivity.After the message is received, loan approver is asked whether the loan will be approved or rejected. Thisis done by invoke activity. Invoke activity is used to call a Web service which has been defined as apartner. Like reply, a partnerLink and operation have to be specified. Executable BPEL is requestresponseoperation where both input and output variable are required.After decision is made by loan approver, the result is sent to applicant via reply activity. Reply activityprovides means to send a response to partners by specifying a partnerLink and operation. A reply activitycan be only placed after a receive activity with same partnerLink and operation. After reply activity, theprocess ends. The sequence and process tags need to be closed.

The diagram 6.2 shows the sequence of actions executed in loan approval process. WApplicant2Requestcontainer1634Loan approverWeb servie4Approvalcontainer1: Applicant sends message2: Message is stored in request container3 & 4: Invocation of Web serviced5: Message from invocation is stored in approval container6: Result is sent to applicantFigure 6.2: The sequence of actions executed in loan approval processThe BPEL process can be run from BPEL engine which has been available in the market (See section 2.1)7. CONCLUSIONSBPEL is convergence of language features of IBM’s WebService Flow Language (WSFL) andMicrosoft’s XLANG. As an XML-based language, BPEL describes the logic to coordinate Web servicesin a process flow. BPEL was first proposed by Microsoft, IBM and BEA as BPEL4WS in August 2002.On 12 April 2007 BPEL 2.0 was approved as OASIS standard. BPEL process needs to be run via BPELengines, which have been developed by several vendors.BPEL-WS provides a standard language for business orchestration and execution. By using BPEL itmakes integration with business partners easier and more effective, it also leas to further processoptimization.However, BPEL does not cover human interaction. To support a broaden range of scenarios, BPELextensions are required. In June 2007, Active Endpoints, Adobe, BEA, IBM, Oracle and SAP publishedthe BPEL4People specifications, which define an approach for integrating human interactions using WS-BPEL 2.0. The specifications will be sent to OASIS for approval in the near future

Besides excluding people action, BPEL does not interaction between sub-process and parent processeither. In September 2005, IBM and SAP published a white paper called Extensions for Sub-Processes(BPEL-SPE). The paper recognizes the problem of process reused in BPEL, describes differentinvocation scenarios and coordination mechanisms between parent process and sub/process. However, noconsensus on how the problem should be resolved. Many efforts still need to be made before BPEL-SPEspecification is finalized.In order to improve the interaction between IT and business process management, EU founded projectSUPER was kicked off on 1st April 2006. The project intends to adopt Semantic Web Servicestechnology to enable business to use information technology more efficiently and to make cooperationbetween IT and business better.8. REFERENCE[1] Matjaz B. Juric, A Hands-on Introduction to BPEL, accessed 09 DEC 2007,URL: http://www.oracle.com/technology/pub/articles/matjaz_bpel1.html[2] Wikipedia, 2007, Business Process Execution Language, accessed 09 DEC 2007,URL: http://en.wikipedia.org/wiki/Business_Process_Execution_Language[3] 2005, Business Process Executive Language, accessed 09 DEC 2007,URL: http://www.expresscomputeronline.com/20050321/technology05.shtml[4] Christoph Schittko, 2003, XML conference & Exposition, Web Service Orchestration with BPEL,accessed 09 DEC 2007,URL: http://www.idealliance.org/papers/dx_xml03/papers/04-06-01/04-06-01.html[5] Michael Cobban, 2004, What is BPEL and why is it so important to my business? accessed 09 DEC2007,URL: http://www.softcare.com/whitepapers/wp_whatis_bpel.php[6] Oracle White Paper, 2004, Orchestrating Web Sevices: The case for a BPEL Server, accessed 09 DEC2007,URL: http://www.oracle.com/technologies/integration/pdf/bpel-case-whitepaper.pdf[7] 2007, The approval of WS-BPEL as OASIS standard, accessed 09 DEC 2007,URL: http://www.oasis-open.org/cn/news/2007_04_12.htm[8] Ta’id Holmes, 2007, BPEL4People: extending WE-BPEL for People, accessed 09 DEC 2007,URL:http://bpel4people.svn.sourceforge.net/viewvc/%2Acheckout%2A/bpel4people/doc/thesis/thesis.pdf?revision=1,[9] 2007, WS-BPEL Extension for People, accessed 09 DEC 2007,URL:http://www.ibm.com/developerworks/webservices/library/specification/ws-bpel4people/[10] Yoichi Takayama, 2007, WS-BPEL Extension for People, accessed 09 DEC 2007,URL:http://wiki.ramp.org.au/confluence/display/workflow/WS-BPEL+Extension+for+People+(BPEL4People)[11] Wikipedia, 2007, BPEL4People, accessed 09 DEC 2007,URL: http://en.wikipedia.org/wiki/BPEL4People[12] 2007, BPEL4People Specifications Integrate Human Interactions Into Business Process, accessed 09DEC 2007,URL: http://xml.coverpages.org/ni2007-06-25-a.html[13] Ashish Agrawal, etal., 2007, WS-BPEL Extension for People Version 1.0,http://xml.coverpages.org/BPEL4People-V1-200706.pdf[14] Ashish Agrawal, etal., 2007, Web Services Human Task Version1.0, accessed 09 DEC 2007,URL: http://xml.coverpages.org/WS-HumanTask-V1-200706.pdf