ocol network modelling", describes protocol network model- ling and protocol design methods. This subject has a chapter of its own because protocol network design constitutes the "glue" between models that are distribu- Preface tion transparent and models that are not. The protocol design method that is pre- sented is based on how abstract networks are defined (according to Chap. 7). This chapter is intended for readers who have to design protocols in distributed systems. Supplementary information is given in Appendix 1-2. The book refers many standards (most of them from the telecom systems domain). There are also many standards that have influenced the methodology. Appendix 1, "List of stand- ards", gives references to all those standards. Most textual specification methods that are presented in the book are based on the ITU-T data specification language ASN.1 For readers who are not familiar with ASN.1, Appendix 2, "Naming and data typing in AML", provides the basis of ASN.1, and indicates how ASN.1 is applied in AML. Some general comments about how the book is written are also in order. Although the book is about paradigms, concepts, language and notations for sys- tems modelling, I tried to avoid being too formalistic. I have focused more on explaining meanings with concepts than on how to represent them in models. The method I have used is primarily exemplification on well-known telecom system concepts, like ISDN, ATM, IP, GSM, etc. (since that is where my domain knowledge lies). Although I believe that describing meaning through examples is an efficient method, I also realize the risk for confusing readers who are not familiar with the telecom domain. To compensate for the choice of examples, I have included basic information about ISDN, etc., to an extent that should allow most readers to follow the discussion. However, since the book is about modelling, not about telecommunications, I had to be quite restrictive with this type of information. My success in keeping everybody on board is for the honoured r