Sun, SAP, BEA and Intalio don't disappoint. Intent on joining complex business processes modeling with collaboration via Web services, the four offer up their recently developed WSCI (Web Service Choreography Interface) specification. WSCI is intended to help model complex business processes, thereby defining and constraining the flow of messages between Web services -- all via XML.
Sounds exciting, but it's hard to differentiate between WSCI and existing specifications intended to provide the same functionality. BPML.org's BPML (Business Process Modeling Language) has had these same types of mechanisms since it was introduced in early 2001. IBM offers similar features with its WSFL (Web Services Flow Language).
While Sun defends WSCI and positions the spec as a "complement" to WSFL and BPML, it also claims that WSCI will be more comprehensive and secure than the other specifications.
What's a developer to do? Don't sweat it for now. WSCI and the like are designed for business-to-business communication. In contrast, most Web services deployments are confined to within organizations, where they will likely stay for some time. When it does come time for you to choose, I suspect that a single standard will emerge, and that standard is the one you'll want to support.