Description

The Web Services Business Process Execution Language (WS-BPEL, BPEL for short) is a programming language to describe the control flow of business processes. BPEL has native support for concurrency, backward and forward recovery. A BPEL process is executed via a workflow engine. Using these engines, a BPEL process can execute for years. IBM, Oracle and Microsoft are some the big players in this field and provide workflow engines which can execute BPEL processes.

The syntax of BPEL is based on XML infoset. Since it is uncommon to write programs using XML, the group around Apache ODE made the proposals BPEL4coders, simBPEL and SimPEL. BPELscript is based on these proposals and provides

a compact syntax inspired by scripting languages such as JavaScript and Ruby
the full coverage of all features provided by BPEL
a translation from WS-BPEL 2.0
a translation to WS-BPEL 2.0.

The translation to WS-BPEL 2.0 ensures that BPELscript can be executed on all workflow engines supporting WS-BPEL 2.0. To enable programmers to maintain WS-BPEL 2.0 code, the translation of WS-BPEL 2.0 to BPELscript allows them to modify the code in a syntax more common to programmers.

Example

namespace pns = "http://example.com/loan-approval/";
namespace lns = "http://example.com/loan-approval/wsdl/";

@type "http://schemas.xmlsoap.org/wsdl/"
import lServicePT = lns::"loanServicePT.wsdl";

@suppressJoinFailure
process pns::loanApprovalProcess {
    partnerLink customer = (lns::loanPartnerLT, loanService, null),
    approver = (lns::loanApprovalLT, null, approver),
    assessor = (lns::riskAssessmentLT, null, assessor);
    try {
        parallel {
            @portType "lns::loanServicePT" @createInstance
            request = receive(customer, request);
            signal(receive-to-assess, [$request.amount &lt; 10000]);
            signal(receive-to-approval, [$request.amount >= 10000]);
        } and {
            join(receive-to-assess);
            @portType "lns::riskAssessmentPT"
            risk = invoke(assessor, check, request);
            signal(assess-to-setMessage, [$risk.level = 'low']);
            signal(assess-to-approval, [$risk.level != 'low']);
        } and {
            join(assess-to-setMessage);
            approval.accept = "yes";
            signal(setMessage-to-reply);
        } and {
            join(receive-to-approval, assess-to-approval);
            @portType "lns::loanApprovalPT"
            approval = invoke(approver, approve, request);
            signal(approval-to-reply);
        } and {
            join(approval-to-reply, setMessage-to-reply);
            @portType "lns::loanServicePT"
            reply(customer, request, approval);
        }
    } 
    @faultMessageType "lns::errorMessage"
    catch(lns::loanProcessFault) { |error|
        @portType "lns::loanServicePT" @fault "unableToHandleRequest"
        reply(customer, request, error);
    }
}

Downloads

The grammar of the language expressed in ANTLR and can be downloaded here (pretty printed). Further details of the language are explained in “Translating WS-BPEL 2.0 to BPELscript and Vice Versa”. The source code is available here @ Github.

SimPEL, being developed by a joint Apache ODE / Intalio team (@intalio, @ode 1, @ode 2)

Future Work

Eclipse DLTK Plugin featuring syntax highlighting and auto completion.
Identify and merge common concepts with SimPEL.
Add support for E4X variable assignments.

Publications

Bischof, Marc; Kopp, Oliver; van Lessen, Tammo; Leymann, Frank: BPELscript: A Simplified Script Syntax for WS-BPEL 2.0. In: 2009 35th Euromicro Conference on Software Engineering and Advanced Applications (SEAA 2009).
Bischof, Marc: Translating WS-BPEL 2.0 to BPELscript and Vice Versa, Student Thesis, University of Stuttgart, 2008. PDF

Contact

Marc Bischof <mc dot bischof at googlemail dot com>
Oliver Kopp <oliver dot kopp at iaas dot uni-stuttgart dot de>
Tammo van Lessen <tammo dot van dot lessen at iaas dot uni-stuttgart dot de>

Please report bugs to our issue tracker.

BPELscript