A transformation language is a computer language designed to transform some input text in a certain formal language into a modified output text that meets some specific goal.
Program transformation systems such as Stratego/XT, TXL, Tom, DMS, and ASF+SDF all have transformation languages as a major component. The transformation languages for these systems are driven by declarative descriptions of the structure of the input text (typically a grammar), allowing them to be applied to wide variety of formal languages and documents.
Macro languages are a kind of transformation languages to transform a meta language into specific higher programming language like Java, C++, Fortran or into lower-level Assembly language.
There are also low-level languages such as the Lx family implemented by the bootstrapping method. The L0 language may be considered as assembler for transformation languages. There is also a high-level graphical language built on upon Lx called MOLA.