A framework for modeling transfer protocols

The notion of speci®cation frameworks transposes the framework approach from software development to the level of formal modeling and analysis. A speci®cation framework is devoted to a special application domain. It supplies reusable speci®cation modules and guides the construction of speci®cations. Moreover, it provides theorems to be used as building blocks of veri®cations. By means of a suitable framework, speci®cation and veri®cation tasks can be reduced to the selection, parametrization and combination of framework elements resulting in a substantial support which opens formal analysis even for real-sized problems. The transfer protocol framework addressed here is devoted to the design of data transfer protocols. Speci®cations of used and provided communication services as well as protocol speci®cations can be composed from its speci®cation modules. The theorems correspond to the relations between protocol mechanism combinations and those properties of the provided service which are implemented by them. This article centers on the application of this framework which is discussed with the help of the speci®cation of a sliding window protocol. Moreover the structure of its veri®cation is described. The speci®cation and veri®cation technique applied is based on L. Lamport's temporal logic of actions (TLA). We use the variant cTLA which particularly supports the modeling of process systems. Ó 2000 Elsevier Science B.V. All rights reserved.