usefor-usefor-04 May 2005

3.1.6  Path

   The Path header indicates the route taken by an article since its
   injection into the Netnews system.  Each agent that processes an
   article is required to prepend one (or more) identities to this
   header.  This is primarily to enable relaying agents to avoid sending
   articles to sites already known to have them, in particular the site
   they came from, and additionally to permit tracing the route articles
   take in moving over the network, and for gathering Usenet statistics.
   path            =  "Path:" SP path-list CRLF

   path-list       =  [FWS]
            *( ( path-identity / path-keyword ) [FWS]
            path-delimiter [FWS] )
            tail-entry [FWS]


   path-identity   =  ( ALPHA / DIGIT )
            *( ALPHA / DIGIT / "-" / "." / ":" / "_" )

   path-keyword    = "POSTED" / "MISMATCH"

   tail-entry      =  path-identity

   path-delimiter  =  "!" / "!!"

   Each <path-identity> in the <path-list> (excluding the one in the
   <tail-entry>) indicates, from right to left, the successive agents
   through which the article has passed.  The <keyword> "POSTED"
   indicates that the agent to its left injected the article.  The use
   of the <path-delimiter> "!!" indicates that the agent to its left
   claims that the agent to its right was the verified source of the
   article (whereas the <path-delimiter> "!" implies no such claim).
   The <keyword> "MISMATCH" indicates that the agent to its right failed
   to be so verified.  The full procedure for constructing a Path header
   as well as the specific format and use of <path-identity> and <tail-
   entry> are discussed in [USEPRO].

      NOTE: Historically, the <tail-entry> indicated the name of the
      sender.  If not used for this purpose, the string "not-for-mail"
      is often used instead (since at one time the whole path could be
      used as a mail address for the sender).

      NOTE: Although case-insensitive, it is intended that the <path-
      keyword>s "POSTED" and "MISMATCH" should be in upper case, to
      distinguish them from the <path-identity>s which are traditionally
      in lower case.

--- ../usefor-usefor-03/Path.out          April 2005
+++ ../usefor-usefor-04/Path.out          May 2005
@@ -7,20 +7,42 @@
    articles to sites already known to have them, in particular the site
    they came from, and additionally to permit tracing the route articles
    take in moving over the network, and for gathering Usenet statistics.
-
    path            =  "Path:" SP path-list CRLF
 
    path-list       =  [FWS]
-            *( path-identity [FWS] path-delimiter [FWS] )
+            *( ( path-identity / path-keyword ) [FWS]
+            path-delimiter [FWS] )
             tail-entry [FWS]
 
+
    path-identity   =  ( ALPHA / DIGIT )
             *( ALPHA / DIGIT / "-" / "." / ":" / "_" )
 
+   path-keyword    = "POSTED" / "MISMATCH"
+
    tail-entry      =  path-identity
 
-   path-delimiter  =  "!" ; possible other delimiters TBD
+   path-delimiter  =  "!" / "!!"
 
-   The specific format and use of <path-identity> and <tail-entry> are
-   discussed in [USEPRO].
+   Each <path-identity> in the <path-list> (excluding the one in the
+   <tail-entry>) indicates, from right to left, the successive agents
+   through which the article has passed.  The <keyword> "POSTED"
+   indicates that the agent to its left injected the article.  The use
+   of the <path-delimiter> "!!" indicates that the agent to its left
+   claims that the agent to its right was the verified source of the
+   article (whereas the <path-delimiter> "!" implies no such claim).
+   The <keyword> "MISMATCH" indicates that the agent to its right failed
+   to be so verified.  The full procedure for constructing a Path header
+   as well as the specific format and use of <path-identity> and <tail-
+   entry> are discussed in [USEPRO].
+
+      NOTE: Historically, the <tail-entry> indicated the name of the
+      sender.  If not used for this purpose, the string "not-for-mail"
+      is often used instead (since at one time the whole path could be
+      used as a mail address for the sender).
+
+      NOTE: Although case-insensitive, it is intended that the <path-
+      keyword>s "POSTED" and "MISMATCH" should be in upper case, to
+      distinguish them from the <path-identity>s which are traditionally
+      in lower case.