Protocols

William Hegait's protocols 1547-76

Principles of Protocol Design

This book introduces the reader to the principles used in the construction of a large range of modern data communication protocols. The approach we take is rather a formal one, primarily based on descriptions of protocols in the notation of CSP. This not only enables us to describe protocols in a concise manner, but also to reason about many of their interesting properties and formally to prove certain aspects of their correctness with respect to appropriate speci?cations. Only after considering the main principles do we go on to consider actual protocols where these principles are exploited. This is a completely new edition of a book which was ?rst published in 1994, where the main focus of many international efforts to develop data communication systems was on OSI – Open Systems Interconnection – the standardised archit- ture for communication systems developed within the International Organisation for Standardization, ISO. In the intervening 13 years, many of the speci?c protocols - veloped as part of the OSI initiative have fallen into disuse. However, the terms and concepts introduced in the OSI Reference Model are still essential for a systematic and consistent analysis of data communication systems, and OSI terms are therefore used throughout. There are three signi?cant changes in this second edition of the book which p- ticularly re?ect recent developments in computer networks and distributed systems.

A Protocol-theoretic Framework for the Logic of Epistemic Norms

This book defines a logical system called the Protocol-theoretic Logic of Epistemic Norms (PLEN), it develops PLEN into a formal framework for representing and reasoning about epistemic norms, and it shows that PLEN is theoretically interesting and useful with regard to the aims of such a framework. In order to motivate the project, the author defends an account of epistemic norms called epistemic proceduralism. The core of this view is the idea that, in virtue of their indispensable, regulative role in cognitive life, epistemic norms are closely intertwined with procedural rules that restrict epistemic actions, procedures, and processes. The resulting organizing principle of the book is that epistemic norms are protocols for epistemic planning and control. The core of the book is developing PLEN, which is essentially a novel variant of propositional dynamic logic (PDL) distinguished by more or less elaborate revisions of PDL’s syntax and semantics. The syntax encodes the procedural content of epistemic norms by means of the well-known protocol or program constructions of dynamic and epistemic logics. It then provides a novel language of operators on protocols, including a range of unique protocol equivalence relations, syntactic operations on protocols, and various procedural relations among protocols in addition to the standard dynamic (modal) operators of PDL. The semantics of the system then interprets protocol expressions and expressions embedding protocols over a class of directed multigraph-like structures rather than the standard labeled transition systems or modal frames. The intent of the system is to better represent epistemic dynamics, build a logic of protocols atop it, and then show that the resulting logic of protocols is useful as a logical framework for epistemic norms. The resulting theory of epistemic norms centers on notions of norm equivalence derived from theories of process equivalence familiar from the study of dynamic and modal logics. The canonical account of protocol equivalence in PLEN turns out to possess a number of interesting formal features, including satisfaction of important conditions on hyperintensional equivalence, a matter of recently recognized importance in the logic of norms, generally. To show that the system is interesting and useful as a framework for representing and reasoning about epistemic norms, the author applies the logical system to the analysis of epistemic deontic operators, and, partly on the basis of this, establishes representation theorems linking protocols to the action-guiding content of epistemic norms. The protocol-theoretic logic of epistemic norms is then shown to almost immediately validate the main principles of epistemic proceduralism.