The 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.