RFC 2396                   URI Generic Syntax                August 1998


G. Summary of Non-editorial Changes

G.1. Additions

   Section 4 (URI References) was added to stem the confusion regarding
   "what is a URI" and how to describe fragment identifiers given that
   they are not part of the URI, but are part of the URI syntax and
   parsing concerns.  In addition, it provides a reference definition
   for use by other IETF specifications (HTML, HTTP, etc.) that have
   previously attempted to redefine the URI syntax in order to account
   for the presence of fragment identifiers in URI references.

   Section 2.4 was rewritten to clarify a number of misinterpretations
   and to leave room for fully internationalized URI.

   Appendix F on abbreviated URLs was added to describe the shortened
   references often seen on television and magazine advertisements and
   explain why they are not used in other contexts.

G.2. Modifications from both RFC 1738 and RFC 1808

   Changed to URI syntax instead of just URL.

   Confusion regarding the terms "character encoding", the URI
   "character set", and the escaping of characters with %
   equivalents has (hopefully) been reduced.  Many of the BNF rule names
   regarding the character sets have been changed to more accurately
   describe their purpose and to encompass all "characters" rather than
   just US-ASCII octets.  Unless otherwise noted here, these
   modifications do not affect the URI syntax.

   Both RFC 1738 and RFC 1808 refer to the "reserved" set of characters
   as if URI-interpreting software were limited to a single set of
   characters with a reserved purpose (i.e., as meaning something other
   than the data to which the characters correspond), and that this set
   was fixed by the URI scheme.  However, this has not been true in
   practice; any character that is interpreted differently when it is
   escaped is, in effect, reserved.  Furthermore, the interpreting
   engine on a HTTP server is often dependent on the resource, not just
   the URI scheme.  The description of reserved characters has been
   changed accordingly.

   The plus "+", dollar "$", and comma "," characters have been added to
   those in the "reserved" set, since they are treated as reserved
   within the query component.







 
RFC 2396                   URI Generic Syntax                August 1998


   The tilde "~" character was added to those in the "unreserved" set,
   since it is extensively used on the Internet in spite of the
   difficulty to transcribe it with some keyboards.

   The syntax for URI scheme has been changed to require that all
   schemes begin with an alpha character.

   The "user:password" form in the previous BNF was changed to a
   "userinfo" token, and the possibility that it might be
   "user:password" made scheme specific. In particular, the use of
   passwords in the clear is not even suggested by the syntax.

   The question-mark "?" character was removed from the set of allowed
   characters for the userinfo in the authority component, since testing
   showed that many applications treat it as reserved for separating the
   query component from the rest of the URI.

   The semicolon ";" character was added to those stated as being
   reserved within the authority component, since several new schemes
   are using it as a separator within userinfo to indicate the type of
   user authentication.