bpelscript

Marc Bischof, Oliver Kopp, Tammo van Lessen, Frank LeymannInstitute of Architecture of Application Systems

[email protected]

A Simplified Script Syntax for WS- BPEL 2.0

35th Euromicro ConferenceSoftware Engineering and Advanced Applications (SEAA 2009)

Presented by Oliver Kopp

Overview

Main Motivation

Existing Approaches

BPELscript

Outlook

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Graphical Model

Abstract BPEL

Executable BPEL

<opaqueActivity><documentation>Set approved to "yes"

</documentation></opaqueActivity>

<assign><copy>

<literal>yes</literal></copy><to variable="approval" part="accept" />

</assign>

deployment

transformation

manual refinement

01100111010100100010010001001110110101

Usual MDD Approach

BPEL: WS-Business Process Execution Language3

© Oliver Kopp 4

Existing Approaches

Presented by Oliver Kopp 5

© Oliver Kopp 7

Our Idea: BPELscript


Goals of BPELscript development

Ease development of executable business processes (AKA “workflows”)

Syntax close to “usual” programming languages

Same semantics as WS-BPEL… enables two-way transformation

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simPEL


Interaction With Partners

partnerLink customer = (lns::loanPartnerLT, loanService, null)Declares a partnerlink customerof partner link type lns::loanPartnerLTwith self-role loanService and no partner role

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Client

loanPartnerLT

Loan ApprovalProcess

loanServicePTloanRequest(nothing)


Receiving a Message

@createInstancerequest = receive(customer, loanRequest);

Annotations for optional attributes in BPELImplicit variable declaration“customer” is the partner link to use“loanRequest” is the operation

Each statement in BPELscript can be seen as an activity in BPEL

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Invoking a Service Operation

risk = invoke(assessor, check, request);

Synchronous service call to risk “assessor”Operation “check”Input variable “request”Result is stored in variable “risk”

Reuse of existing processes is done by using the processes by invokes, receives, …BPEL does not allow the definition of new “procedures”

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Aynchronous Variant

invoke(assessor, check, request, {assessorCorrelation});

risk = receive(assessor, checkResult,{assessorCorrelation});

Optional Parameter lists correlation sets to use for correlatoin

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Variable Assignment

approval.accept = "yes";

Default expression language: E4XECMAScript for XMLTranslated to assign or kept as E4X

T. van Lessen and others: Facilitating Rich Data Manipulation in BPEL using E4X. In ZEUS 2009

XPath still supportedvar = [bpel:doXslTransform("...", $A)];

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Replying to a Synchronous Call

reply(customer, loanRequest, approval);

Reply message for the “loanRequest” operationNo correlation needed

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Linking Activities Together

Just as in usual programming languages

@createInstancerequest = receive(customer, loanRequest);risk = invoke(assessor, check, request);if (risk.level=="high") {approval.accept = "no";

} else {approval.accept = "yes";

}reply(customer, loanRequest, approval);

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What about Graphs?

Process modeling languages offer“graph-oriented programming”BPEL also offers graph-oriented programmingTwo alternatives to represent it in BPEL

A) Map to matching block-constructsB) Use BPEL’s graph capabilities

An activity is a node in the graphA link representes an edge in the graph

16J. Vanhatalo & H. Völzer & J. Koehler: The Refined Process Structure Tree BPM'08


Graph-oriented Programming: Alternatives

Goto-inspired syntaxlauto: risk = invoke(…)l1=[$risk = 'high']‐>lhuman, l2=[$risk != 'high']‐>lapp[l1 and l2] lapp: invoke(…);

Signal and Join Statementsrisk = invoke(…)signal(l1, [$risk.level == 'low']);signal(l1, [$risk.level != 'low']);join(l1, l2, [$l1 and $l2]);

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Resulting Process

parallel {@createInstancerequest = receive(customer, loanRequest);signal(receive‐to‐assess,[$request.amount < 10000]);

signal(receive‐to‐approval,[$request.amount >= 10000]);

} and {join(receive‐to‐assess);risk = invoke(assessor, check, request);...

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Fault Handling

try {...} catch(lns::loanProcessFault) { |error|@fault unableToHandleRequestreply(customer, loanRequest, error);

}

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Advanced Workflow Constructs

scope {...} onEvents {event(partnerLink, operation) {...}timeOut(...) {...}

} onTermination {...

} onCompensation {...

}20


Overview on the Transformation

ANTLR: ANother Tool for Language RecognitionParser Generator

ANTXR: ANother Tool for Xml RecognitionXML Processing for ANTLR

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Future Work

IDE for BPELscript

Enhance the translator to support implicit variable declaration

Compare efficiency of BPEL development and BPELscript development

Follow development athttp://www.bpelscript.org/

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bpelscript

Technology