--- /dev/null
+ V. Wagner
+ March,2008
+
+ Distributed Blog Commenting Prototcol
+
+Status of this Memo
+
+ I just write it. If considerable interest appear, we might submit it
+ to the IETF as RFC draft
+
+Copyright
+
+ Copyright (c) by Victor B. Wagner, 2008
+
+Abstract
+
+ This document describes a protocol which can be used by different
+ blog sites and web-based RSS aggregators to exchange the comments,
+ made by users to the blog entries either originating on this site
+ or recieved from other sites.
+
+
+1 Introduction
+
+1.1 Purpose of protocol
+
+ Some blog sites are more like discussion forums. They allow reader
+ to comment on blog entries identifying themselfes using some
+ identity such as OpenID. If it is quite possible to distribute blog
+ entries to other (mirror) sites using protocols like RSS/Atom feeds,
+ to distribute load and improve availability of particular blog,
+ there is no way to allow users to make comments on mirror site and
+ distribute this comments to all other copies of same blog.
+
+ Proposed protocol closes this gap.
+
+1.2 Requrements
+
+ Sites participating in this protocol should be able to serve http
+ request [HTTP] and send those.
+
+1.3 Terminology
+
+ The capitalized key words "MUST", "MUST NOT", "REQUIRED", "SHALL",
+ "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
+ "OPTIONAL" in this document are to be interpreted as described in BCP
+ 14, RFC 2119 [TERMS].
+
+2 Protocol overview
+
+2.1 Basic terms definition
+
+2.1.1 BLOG
+
+ Blog or weblog is a web resource typically consisting of series of
+ messages (POSTS) which appear on the blog web-page starting from
+ most recent one. Each blog post can have separate web page, but it
+ is guaranteed, that by visiting well-known and constant blog URL
+ any HTTP-client would get most recent post first.
+ Typically web page on this URL contain some special links which
+ point to RSS feed of the posts, author information (FOAF) open-id
+ server which confirms blog owner identity etc. For the purposes of
+ this protocol blog is identified by this URL.
+
+
+2.1.2 User
+
+ User is an entity which can prove identity to at least to one of
+ the servers. This server can confirm this identity to other servers
+ with OpenID or simular means. So, comments made by the user carry
+ user identity verified by the server either directly or indirectly
+ via another server.
+
+2.1.3 Comment
+
+ Piece of textual information associated with some post in the
+ particular blog and, may be with another comment to the same post.
+
+2.2 Required comment proprieties
+
+ Each comment in the system which support this protocol MUST have
+ following proprieties:
+
+2.2.1 Comment text
+
+ Fragment of the text which MAY contain some XHTML markup, including
+ references to other web resourses, including another comments,
+ blogs or blog posts.
+
+2.2.2 Globally unique identifier
+
+ Globaly unique identifier is created by site where comment was
+ originally posted. It MUST contain hostname of the originating site
+ and some string which ensures uniqueness among other comments
+ originatig to this site
+
+2.2.3 Blog, where comment was posted to
+
+ Original URL of blog where comment belong
+
+2.2.4 Blog post where comment was posted to
+
+ Permanent URL of blog post on its originating site. This URLs
+ are always included into RSS/Atom feeds, so any mirror site would
+ have no problem determining this URL
+
+2.2.5 Original posting date
+
+ Timestamp with precision of second when comment is posted
+
+ Also comments might have following OPTIONAL properities
+
+2.2.6 Author
+
+ URL of verified user identitity of user, who submitted this comment.
+ If idenitity was provided via OpenID or similar protocol, it MUST
+ have
+ form of URL. If user authenticated on the site, where comment was
+ submitted, directly it SHOULD be OpenID URL which would prove identity
+ of this user to other sites.
+
+ Sites participating in this protocol MAY allow anonymous comments.
+ If comment is anonymous, Author propriety MUST be omitted from
+ this comment.
+
+2.2.7 Modification time
+
+ If comment was changed after its initial submission, it MUST contain
+ additional timestamp specifying last change date. Servers conforming
+ to this protocol SHOULD allow comment author to change comments.
+
+ There is one special case - deletion of comments. Owner of blog,
+ i.e. user with same identity as blog url SHOULD be able to delete
+ any comments in his blog.
+
+2.2.8 Reference to parent comment
+
+ If site allows to comment on another comment in the blog entry, not
+ only blog entry itself, unique identificator of parent comment
+ SHOULD be recorded as comment propriety. If this propriety is
+ absent, any server, recieving this comment, SHOULD assume that it is
+ made on blog entry itself.
+
+3. Comment exchange protocol
+
+3.1 URL structure
+
+ Any site participating in this protocol should provide following
+ web resouces:
+
+3.1.1. Blog list
+
+ Page which lists blogs, which can be commented on this site
+ This page should have content type text/plain and list blog URLs
+ one per line
+
+3.1.2. Comment list
+
+ If URL consisting of BLOG list URL, slash ("/") and blog URL is
+ requested via HTTP GET method, it should return text/plain list of
+ recent comments (most recent first) in the form
+
+ timestamp whitespace comment-id
+
+ one per line.
+ If this URL is requested with skip=number parameter (i.e. appended
+ with question mark, workd skip equal sign and number), it should
+ return list of more earlier comments.
+
+3.1.3 Comments itself
+
+ If URL described in 3.1.2 is requested via POST method and POST
+ request body consists of list of comment identifiers, separated by
+ newlines, it should return text/xml data containing specified
+ comments using XML schema described in the section 4 of this
+ document.
+
+ Comments MAY be ordered either earliest first or in order listed in
+ the request.
+
+ Any conforming implementation sending the request SHOULD send
+ identifiers of requested comments from earliest to latest.
+
+3.1.4 Posting notification
+
+ Conforming implementation should understand request to the URL 3.1.1
+ either by POST by or GET method,
+ which contains parameter notify=blog-URL. This request means that
+ site sending this request wants to notify this site that it have new
+ comments on the specified blog.
+
+ If blog-URL doesn't belong to this site, it MAY respond to this
+ request with 406 (Not Acceptable) HTTP response code.
+
+ Otherwise it should respond with 200 response and immediately
+ initiate procedure of recieving comment from the site which sent
+ request.
+
+ Conforming implementation SHOULD send notify requests only if
+ comment was posted on the site to the blog originating on the site
+ where request is sent, unless it is behind firewall or proxy. In
+ this case it MAY send such requests for each blog commented on it
+ to some relay site, if permitted by the relay site administrator.
+
+ If notifying site is behind NAT or firewall and connection cannot to
+ it cannot be stablished, reverse protocol described in section 3.3.3
+ could be used.
+
+
+3.2 Declaring support of this protocol
+
+3.2.1 Declaring support in the protocol on the blog page
+
+ Each site which supports this protocol SHOULD add link tag to its
+ blog pages with rel="comment-exchange" and href pointing to URL,
+ described in the section 3.1.1.
+
+3.2.2 Declaring protocol URL during comment exchange.
+
+ Each site which performs comment exchange procedure should provide
+ its peers means to retrieve comments from it. This is done by adding
+ custom HTTP header X-Comment-Exchange-URL to all requests to
+ protocol pages. This header should contain URL of page described in
+ 3.1.1, and host name in this URL MUST resolve to the same IP address
+ request is made from.
+
+
+3.3. Connect exchange procedure
+
+3.3.1 Procedure initiation.
+
+ Site supporting this protocol SHOULD check presense of link
+ rel=comment-exchange on all sites it retrieves blog entries via
+ RSS/Atom. If this link is found it MAY periodically initiate comment
+ exchange procedure with these sites.
+
+ It also MAY initiate this procedure with any site which was known
+ to initiate this protocol with it before.
+
+ If 404 NOT FOUND HTTP response code is recieved when requesting URL
+ 3.1.1, this site SHOULD be removed from the list of polled sites
+ until either explicit user interaction or first protocol session
+ initiated from that site.
+
+3.3.2 Normal (PULL) procedure
+
+ 1. Site requests lists of blogs from URL 3.1.1
+ 2. For each blog interesting to this site, list of available
+ comments is requesed from URL 3.1.2. If site has reasonable
+ expectations that it can miss some comments, which are not
+ listed on first page, request page multiple times using skip
+ parameter.
+ 3. Prepare list of missing comments, earliest first and send it to
+ site
+ 4. Repeat steps 2,3 for each blog copy of each is carried on this
+ site.
+
+3.3.3. Reverse (PUSH) procedure
+
+ 1. Send notify request (3.1.4) using POST method with list of
+ available comments as specified in 3.1.3 in the POST body.
+
+ 2. Recieve list of requested comments as text/plain resoponse to
+ the POST request.
+
+ 3. Send XML stream of the comments using POST request to the same
+ URL with content type text/xml
+
+ 4. Repeat steps 1-4 for each blog comments for which are to be
+ pushed to this site.
+
+ when using PUSH method X-Comment-Exchange-URL header MAY be omitted.
+
+
+4. Comment stream XML format
+
+4.1 Comment stream XML document have <comment-stream> root node.
+ Contents of this stream is sequence of <comment> element.
+4.2 Comment element should contain following elements
+ <comment-id>unique-identifier</comment-id>
+ <blog>blog-URL</blog>
+ <post>post-URL</post>
+ <parent-id>unique-identifier</parent-id>
+ <author>url</author>
+ <posted>date</posted>
+ <edited>date</edited>
+ <body>text of comment with optional XHTML markup</body>
+ Some of this elements are OPTIONAL (see section ).
+
+4.3. Comment deletion
+ If comment element contain element
+ <deleted/> and <author> element contains either same URL as
+ original comment with same <comment-id> or URL of blog, comment
+ belongs to,
+ comment with given identifier should be removed
+ from the user's view, but deletion notice retained in the database
+ in case that same
+ comment would be sent from other site which didn't have recieved
+ deletion message yet.
+
+
+4.4 Banning user from commenting.
+ If comment element contains element
+ <ban set="1">identity URL</ban> instead of body or along with
+ <delete> element,
+ and comment author identity is same as
+ identity of blog it belongs to, it means that user with given
+ identity should no more be allowed to comment in this blog, and any
+ existing comments from this user should not be offered to other
+ sites, requesting comments using this protocol, even if these
+ comments has earlier timestamp than ban notice.
+
+4.5 Removing ban
+
+ If comment element contain element
+ <ban set="0">identity URL</ban> than previously set ban should be
+ removed.
+
+5. Full Copyright Statement
+ Would write it if document is to be submitted to the IETF as RFC
+ draft
+
+
+
+
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