# Xpand / Xtend / Check Reference

## Introduction

The Xpand generator framework provides textual languages, that are useful in different contexts in the MDSD process (e.g. validation, metamodel extensions, code generation, model transformation). Each language ( Check , Xtend , and Xpand ) is built upon a common expression language and type system. Therefore, they can operate on the same models, metamodels and meta-metamodels and you do not need to learn the syntax again and again, because it is always the same.

The expressions framework provides a uniform abstraction layer over different meta-meta-models (e.g. EMF Ecore, Eclipse UML2, JavaBeans, XML Schema etc.). Additionally, it offers a powerful, statically typed expressions language, which is used in the various textual languages.