IBM published Web Services Flow Language[*] in 2001 with the familiar purpose of standardizing the
design of web-service-oriented business processes spanning multiple
participants. WSFL has so much in common with BPML, WSCI, XLANG, BPEL,
and other XML-based process languages that given also its complete
lack of industry support, it is tempting to discount it entirely.
Indeed, even IBM has given up on it, but only because IBM decided to
join forces with Microsoft and BEA on BPEL. As it turns out, IBM's
involvement in the design of BPEL resulted in core WSFL ideas (e.g.,
flow, dead path elimination)
infiltrating BPEL. WSFL's influence on BPEL makes it worthy of
WSFL supports the definition of two types of process models:
The orchestration of web service operations for a single participant.
The exchange, or choreography, of messages by web service invocation across a set of participants.
The ubiquitous purchasing example (used in countless BPM
discussions) demonstrates a WSFL implementation of both models. Figure 9-9 shows the exchange
of messages between three participants:
Warehouse. Each participant has its own flow
model, shown as the arrangement of circles (representing
activities) and solid arrows (control
links) running from top to bottom starting immediately
below the participant name. The dotted arrows, which connect
activities across different flows, are called plug
links ; the global model ...