Developing collaborative applications over the Web has become increasingly important. In order to accomplish this, Web services need to be extended beyond the basic service architecture (invoke and respond) to self-coordinating Web processes collaborating among themselves (transient to long lasting). A core set of artifacts is needed to allow these Web processes to hook together in a desired structure to enforce automatic information flow, group constraints, and data/control dependencies. We have proposed Web Coordination Bonds as such a set of artifacts with the required theoretical underpinning for effective collaboration among Web services. Here, we establish that Web bonds are at least as powerful as the extended Petri nets (modeling power). We demonstrate their expressiveness by modeling a comprehensive set of benchmark workflow scenarios and distributed communication patterns. Such fundamental treatments are unique, and are essential for further progress in the technology for distributed software over Internet.