BPEL, XLANG, and WSFL
The design of BPEL borrows elements from both XLANG and WSFL. Table 9-3 lists the major BPEL features and their corresponding features in XLANG and WSFL.
BPEL feature | XLANG | WSFL |
Partner, partner links | Business party contracts | Global model, service providers, plug links |
Process variables | No, implicit only | No, implicit only |
Correlation | Correlation sets, correlation
attributes of | |
Exception handling | Per-context exception handler | Weak, use control links to custom exception activities |
Compensation | Per-context compensation handler | |
Scope | | |
Invoke | | Activity |
Receive | | Activity |
Reply | | Activity |
Wait | | |
No op | | Internal activity |
Sequence | | Yes, as graph |
Switch | | Yes, as graph |
While | | Yes, as graph, supports loops |
Pick | | |
Flow | | Flow model, control links |
Assign | ||
Global event handler | ||
Dead path elimination | Inherent support, crucially important concept | |
Subprocess | ||
Process initiation | An | Lifecycle service has |
Two conclusions can be drawn from this survey:
XLANG and WSFL are very different approaches, and, depending on your point of view, coexist either peacefully or tenuously in BPEL. XLANG is programmatic, where programming language-like elements such as
while
,sequence
, andswitch
structure the control ...
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