The Salmon Protocol is a message exchange protocol running over
HTTP
The Hypertext Transfer Protocol (HTTP) is an application layer protocol in the Internet protocol suite model for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web, ...
designed to decentralize commentary and annotations made against newsfeed articles such as blog posts. It allows a single discussion thread to be established between the article's origin and any
feed reader
In computing, a news aggregator, also termed a feed aggregator, feed reader, news reader, RSS reader or simply an aggregator, is client software or a web application that aggregates syndicated web content such as online newspapers, blogs, podc ...
or "aggregator" which is subscribing to the content. Put simply, that if an article appeared on 3 sites: A (the source), B and C (the aggregates), that members of all 3 sites could see and contribute to a single thread of conversation regardless of site they were viewing from.
Example
The origin supplies a Salmon end point – a URL in the metadata of an
RSS
RSS ( RDF Site Summary or Really Simple Syndication) is a web feed that allows users and applications to access updates to websites in a standardized, computer-readable format. Subscribing to RSS feeds can allow a user to keep track of many di ...
/
Atom (standard)
The name Atom applies to a pair of related Web standards. The Atom Syndication Format is an XML language used for web feeds, while the Atom Publishing Protocol (AtomPub or APP) is a simple HTTP-based protocol for creating and updating web re ...
feed. An aggregating site makes a note of the end point.
If a member of the aggregator makes a comment, the aggregator will construct a comment for the benefit of the origin.
tag:example.com,2009:cmt-0.44775718test@example.combob@example.com
tag:blogger.com,1999:blog-893591374313312737.post-3861663258538857954
Salmon swim upstream!Salmon swim upstream!2009-12-18T20:04:03Z
The comment will be base64 encoded, digitally signed, placed in an envelope and POSTed back to the origin via the endpoint.
POST /salmon-endpoint HTTP/1.1
Host: example.org
Content-Type: application/atom+xml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base64urlRSA-SHA256
EvGSD2vi8qYcveHnb-rrlok07qnCXjn8YSeCDDXlbhILSabgvNsPpbe76up8w63i2f
WHvLKJzeGLKfyHg8ZomQ
The comment is then made available by the origin in its original feed so subscriber aggregators may refresh their view of the conversation. The protocol provides security so that each aggregator and each member is uniquely identified so that the upstream could employ measures to ban or filter out rogue sites or members if so desired.
Diaspora
A diaspora ( ) is a population that is scattered across regions which are separate from its geographic place of origin. Historically, the word was used first in reference to the dispersion of Greeks in the Hellenic world, and later Jews after ...
use Salmon as defined in the
OStatus
OStatus is an open standard for federated microblogging, allowing users on one website to send and receive status updates with users on another website. The standard describes how a suite of open protocols, including Atom, Activity Streams, WebS ...
specification to coordinate discussion between members belonging to different servers. A member of one server can publish an article which is disseminated to other users over the network via Salmon who in turn can comment back in a similar fashion.
See also
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RSS
RSS ( RDF Site Summary or Really Simple Syndication) is a web feed that allows users and applications to access updates to websites in a standardized, computer-readable format. Subscribing to RSS feeds can allow a user to keep track of many di ...
*
AtomPub
The name Atom applies to a pair of related Web standards. The Atom Syndication Format is an XML language used for web feeds, while the Atom Publishing Protocol (AtomPub or APP) is a simple HTTP-based protocol for creating and updating web re ...
*
Publish Subscribe
Publishing is the activity of making information, literature, music, software and other content available to the public for sale or for free. Traditionally, the term refers to the creation and distribution of printed works, such as books, newsp ...
*
OStatus
OStatus is an open standard for federated microblogging, allowing users on one website to send and receive status updates with users on another website. The standard describes how a suite of open protocols, including Atom, Activity Streams, WebS ...
(mentions OStatus users, not specifically Salmon protocol use)