Recently the term Web Services Choreography has been introduced to address some issues related to Web
Services Composition and Coordination. Several proposals for describing Choreography for Business Processes have been presented in the last years and many of these languages (e.g. BPEL4WS) make use of
concepts as long-running transactions and compensations for coping with error handling. However, the
complexity of BPEL4WS makes it difficult to formally define this framework, thus limiting the formal reasoning about the designed applications. In this paper, we formally address Web Services Coordination with
particular attention to Web transactions. We enhance our past work - the Event Calculus - introducing two
main novelties: i) a multicast event notification mechanism, and ii) event scope names binding. The former
enables an easier specification of complex coordination scenarios — such as E-commerce applications require
— while the latter allows many new interesting behaviors which can be very useful in business scenarios:
the introduction of private event scope names — used to deal with security and privacy — and a dynamic
event scopes definition that can be used to manage multiple instances of the same applicatio