version 1 .

; Dataspace patterns: a sublanguage of attenuation patterns.
Pattern = DDiscard / DBind / DLit / DCompound .

DDiscard = <_>.
DBind = <bind @name symbol @pattern Pattern>.
DLit = <lit @value any>.
DCompound = @rec  <compound <rec @label any @arity int> @members { int: Pattern ...:... }>
          / @arr  <compound <arr @arity int>            @members { int: Pattern ...:... }>
          / @dict <compound <dict>                      @members { any: Pattern ...:... }> .