val nuprl_dir : string lazy_t (* XMLs' directory for NuPRL*)
val rdf_dir : string lazy_t (* RDFs' directory *)
val dtd_dir : string lazy_t (* DTDs' root directory *)
val nuprl_dir : string lazy_t (* XMLs' directory for NuPRL*)
val rdf_dir : string lazy_t (* RDFs' directory *)
val dtd_dir : string lazy_t (* DTDs' root directory *)