5.3 Formal Public Identifiers (FPIs)

prefix//owner//class description//language//version
-//IETF//DTD HTML 2.0 Strict//EN  
-//W3C//DTD XHTML 1.1//EN  
+//IDN http://www.cis.ohio-state.edu/~gurari//DTD none so far//EN

prefix registered (+), unregistered (-), iso


owner owner identifier


class type of object (e.g., DOCUMWNT, DTD, ENTITIES)


descriptiona unique text description


language two uppercase characters from ISO 639


version optional


The registered (+) prefix may also be used by owners of internet domain names (IDN): +//IDN IDN//... [WEB-SGML TC to ISO 8879]