R. Lee (Ed.): SERA, SCI 496, pp. 85–98. DOI: 10.1007/978-3-319-00948-3_6 © Springer International Publishing Switzerland 201 Towards a Protocol Algebra Based on Algebraic Specifications Iakovos Ouranos and Petros Stefaneas 1* Abstract. We sketch some first steps towards the definition of a protocol algebra based on the framework of behavioural algebraic specification. Following the tradition of representing protocols as state machines, we use the notion of Obser- vational Transition System to express them in an executable algebraic specifica- tion language such as CafeOBJ. This abstract approach allows defining several useful operators for protocol reasoning and proving properties of them using theo- rem proving techniques and CafeOBJ term rewriting machine. The proposed protocol algebra is inspired by the module algebra and the hierarchical object composition technique. Keywords: formal methods, algebraic specification, behavioural specification, protcol algebra, CafeOBJ. 1 Introduction Distributed protocols typically involve several modules interacting with one anoth- er in a complex manner. The design and verification of them are two of the most difficult and critical tasks in the current computing systems development. Many new protocols are designed in the current software industry, and the tradition is to develop them from scratch, i.e. specify them informally and implement them di- rectly into software using a programming language. This makes protocol develop- ment even more painful and risky. A solution to these problems seems to be formal algebraic specification techniques. In this paper we propose the behavioral Iakovos Ouranos Hellenic Civil Aviation Authority, Heraklion Airport, Greece e-mail: iouranos@central.ntua.gr Petros Stefaneas National Technical University of Athens, School of Applied Math. & Phys. Sciences, Greece e-mail: petros@math.ntua.gr 4