B.4 Specification Libraries

  LIB-DEFN         ::= lib-defn LIB-NAME LIB-ITEM*
  LIB-ITEM         ::= SPEC-DEFN | VIEW-DEFN
                     | ARCH-SPEC-DEFN | UNIT-SPEC-DEFN
                     | download-items LIB-NAME ITEM-NAME-OR-MAP+
  ITEM-NAME-OR-MAP ::= ITEM-NAME | item-name-map ITEM-NAME ITEM-NAME
  ITEM-NAME        ::= SIMPLE-ID

  LIB-NAME         ::= LIB-ID | LIB-VERSION
! LIB-ID           ::= direct-link URL | indirect-link PATH
  LIB-VERSION      ::= lib-version LIB-ID VERSION
  VERSION          ::= version NUMBER+