Essential Business Process Modeling

IBM WSFL: BPEL Forerunner

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 investigation.

WSFL supports the definition of two types of process models:

Flow model

The orchestration of web service operations for a single participant.

Global model

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: Consumer, Retailer, and 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 ...