Synchronous sequence charts in action

We identify a number of styles for using Interworkings (synchronous sequence charts), together with their roles in the context of the OS1 reference model. \Ve employ the well-known ABP (alternating bit protocol) to see how Interworkings can and cannot be used. This ex-periment shows that the charts are attractive from an intuitive point of view, but when used in their purest form, lack sufficient expressive power. Some of the distinctions in style can be interpreted as distinct approaches to adding expressive power. Categories and Subject Descriptors: C.2A [Computer communication net-worksJ: Distributed systems- distributed applications; D.2.1O, D3.2 [Softwar