Xsemantics
a DSL for type systems, reduction rules, interpreters for Xtext langs
Xsemantics is a DSL (implemented in Xtext itself) for writing type systems, reduction rules, interpreters (and in general relation
rules) for languages implemented in Xtext. It then generates Java code that can be used in your language implemented in Xtext
for scoping and validation (it can also generate a validator in Java).