WSCL, the least well-known of the choreography approaches, is easy to miss in the hunt for BPM standards. Its 24-page specification, submitted by Hewlett Packard to the W3C in the spring of 2002[*] (ancient history, in BPM timelines), has never caught on with vendors and has not permeated the W3C’s current choreography efforts. It’s too bad, because WSCL’s simple, elegant approach to choreography, using the idea of the state machine, has considerable merit.
WSCL is an XML language whose main construct is a
conversation, which represents a
participant’s web-service-based dialog with the other participants in
the attainment of a business goal. The steps of the conversation are
interactions, in which the
participant either calls or is called by other participants. WSCL
supports four types of interactions, which are summarized in Table 8-2.
Participant reacts to an inbound request message.
Participant sends a message outbound.
Input message, output message, multiple output fault messages
Participant reacts to an inbound request message and sends back a response message.
Output message, input message, multiple input fault messages
Participant sends a message outbound and waits for the response to come back.
The link from one interaction (the source) to another (the
destination) is called a
transition. In the ...