d0sl is a semantic language for writing logical rules (or predicates). d0sl is designed to be as simple as possible, but sufficient to record all logical operations, according to the mathematical theory of semantic modeling.
d0sl can be easy extended with domain specific functions and objects. Thus d0sl itself is DSL (domain specific language).
For d0sl, a language-level extension mechanism is provided. In other words, you can build DSL hierarchies of languages that are transformed into d0sl and can also be executed by the core of d0sl.