The "Oslo" Modeling Language (commonly referred to as "M") is a language for defining domain models and languages (the latter are often referred to as textual DSLs). "M" was created to allow developers to efficiently capture their intention in a form that is natural to author but also efficient to store and query using off-the-shelf database technology. This book comes from the original creators of "M"--David Langworthy, Brad Lovering, and Don Box--and is the definitive reference to the language. If you are looking for a compact textual notation for writing down information or schematizing structured and unstructured data, this book is for you. This book is the authoritative specification of the "M" language (draft) and describes the syntax and underlying model of the language. Highlights of this book include: * An Introduction to domain modeling constructs * An Introduction to constructs for building textual DSLs * Complete syntax for the language * Definition of the "M" type system and data model * Glossary of terms