XLANG

Modeling of business processes as Autonomous Agents. The unit of actions is a Service Process, which consists of a set of operations according to a defined sequence

• Sequential and parallel control flow constructs
• Transaction support
• Custom correlation of messages
• Flexible handling of exceptions
• Dynamic service referral
• Contracts to agglomerate services

XLANG Pros

• Defined as an extension to WSDL
• Availability of complicated control structures and exception handling

XLANG Cons

• Does not enable exporting activities of individual services as part of the workflow
• Does not explicitly handle recursive composition of Web Services
• Relies on the ambiguous outgoing operations of WSDL
• Does not address lifecycle for individual services

XLANG and the pi-calculus

One of the most interesting features of XLANG is the support for explicit exception handling and compensating transactions. Compensating transactions are a crucial emering pattern in the scenario of Service Oriented Computing. Compensation triggering, as implemented by the Microsoft XLANG engine BizTalk, has been modelled with the pi calculus in http://www.cs.unibo.it/~laneve/papers/biztalk.pdf .