Language element is a unit of parsing (e.g. variable definition). <B style="border-bottom:gray dotted 1px">Source unit</B> typically consists of a tree of language elements. Language elements can reference other language elements (e.g. variable reference can reference variable definition) and also they reference <B style="border-bottom:gray dotted 1px">Language element defintion</B>. A language element can reference language elements defined in other languages. For example, EJB deployment descriptor XML element can refernce EJB Java class language elements. This feature is very important for code reviews of nowadays software systems where very often Java (or some other language) code is glued together with XML configuration files, HTML or XML file contain JavaScript scriptlets, etc.