d Standards Appendix B: SAG and SAC Operations Appendix C: AMLn Configuration Parameters and Tables Appendix D: AMLs and AMLp in Short References Index Introduction to Network System Modeling Systems Modeling in General This book presents AMLn (Abstract Modeling Language, network view). AMLn is a proposed language for modeling network systems. We regard as "net- work system" any system that exhibits a structure of nodes and provides connectiv- ity services for humans, machines, and different types of application systems. Network systems are commonly defined by international standards (AMLn is, however, not restricted to standardized systems only). Examples of standardized network systems are the Internet, UMTS, PSTN/ISDN, SS7, GSM, GPRS, ATM, SDH, and diverse LAN concepts (see Appendix A for definitions of acronyms). In this chapter we provide a general background to modeling. When we want to describe something, whether it is an artifact or something more abstract, we can do it verbally, using natural language text in documents (perhaps with some support- ing pictures) or we can build a model of it. A model may be a miniature of an arti- fact, or it may be an information model (the only interpretation of modeling that concerns us in this book). In an information model, parts and relations between parts of the thing we model are represented by information elements. An information model is built by using a modeling language. A modeling lan- guage is designed SO that a model in that language can be understood not just by a human interpreter, but also by an interpreter that runs in a computer system. Thus, a modeling language is a formal language with special qualities for human inter- pretation of models that are constructed in that language. For example: It includes concepts and terms that are familiar to designers and users within a particular system domain (which may be networks, power plants, missiles, soft- ware systems, etc.). It includes graphical representations of important basic language concepts. It allow