must imply a hierarchical structure.

Reserved characters

   The path in the URI has a significance defined by the particular
   scheme.  Typically, it is used to encode a name in a given name
   space, or an algorithm for accessing an object.  In either case, the
   encoding may use those characters allowed by the BNF syntax, or
   hexadecimal encoding of other characters.

   Some of the reserved characters have special uses as defined here.

   THE PERCENT SIGN

      The percent sign ("%", ASCII 25 hex) is used as the escape
      character in the encoding scheme and is never allowed for anything
      else.

   HIERARCHICAL FORMS

      The slash ("/", ASCII 2F hex) character is reserved for the
      delimiting of substrings whose relationship is hierarchical.  This
      enables partial forms of the URI.  Substrings consisting of single
      or double dots ("." or "..") are similarly reserved.

      The significance of the slash between two segments is that the
      segment of the path to the left is more significant than the
      segment of the path to the right.  ("Significance" in this case
      refers solely to closeness to the root of the hierarchical
      structure and makes no value judgement!)








 
RFC 1630                      URIs in WWW                      June 1994


      Note

         The similarity to unix and other disk operating system filename
         conventions should be taken as purely coincidental, and should
         not be taken to indicate that URIs should be interpreted as
         file names.

   HASH FOR FRAGMENT IDENTIFIERS

      The hash ("#", ASCII 23 hex) character is reserved as a delimiter
      to separate the URI of an object from a fragment identifier .

   QUERY STRINGS

      The question mark ("?", ASCII 3F hex) is used to delimit the
      boundary between the URI of a queryable object, and a set of words
      used to express a query on that object.  When this form is used,
      the combined URI stands for the object which results from the
      query being applied to the original object.

      Within the query string, the plus sign is reserved as shorthand
      notation for a space.  Therefore, real plus signs must be encoded.
      This method was used to make query URIs easier to pass in systems
      which did not allow spaces.

      The query string represents some operation applied to the object,
      but this specification gives no common syntax or semantics for it.
      In practice the syntax and sematics may depend on the scheme and
      may even on the base URI.

   OTHER RESERVED CHARACTERS

      The astersik ("*", ASCII 2A hex) and exclamation mark ("!" , ASCII
      21 hex) are reserved for use as having special signifiance within
      specific schemes.

Unsafe characters

   In canonical form, certain characters such as spaces, control
   characters, some characters whose ASCII code is used differently in
   different national character variant 7 bit sets, and all 8bit
   characters beyond DEL (7F hex) of the ISO Latin-1 set, shall not be
   used unencoded. This is a recommendation for trouble-free
   interchange, and as indicated below, the encoded set may be extended
   or reduced.







 
RFC 1630                      URIs in WWW                      June 1994


Encoding reserved characters