RSS Channel & History

RSS Channel & History

RSS was born for practical purposes, as good formats tend to be. The RSS 0.91 spec starts with the words “Files must be 100% valid XML,”It initially started to be known as headline syndication drove development and refinement of the format.

According to dictionary, syndication refers to sell (a comic strip or column, for example) through a syndicate for simultaneous publication in newspapers or periodicals.

The RSS community started calling what it did ‘syndication‘ (as in, “Really Simple Syndication”) because it was all about distributing content for reuse. However, RSS syndication isn’t usually paid for, and it isn’t just for republication; specialized clients called aggregators made content available directly to end users, so that they could mix-and-match their channels at will.

The headline syndication view of RSS is to-the-point; a channel is a reverse-chronological sorted list of links to stories, along with metadata for each one indicating the title and sometimes a description.

This metadata summary view of RSS (“Rich Site Summary” or “RDF Site Summary”) treated the channel as a container for any kind of statement – from market data to mp3 playlists to event calendars or even order systems – as long as what they were talking about could be arranged in a list. The modularity of RSS1.0 enables its use in a variety of contexts, from Wall Street to Open Source software distribution.

Last but not least, Weblogs have been using RSS for completely different – content syndication. Instead of just saying things about the channels’ links, they reproduce the content at the other end, so that a Web resource can be replicated in whole in an aggregator or on another site.

Items are well-understood (having identifiers and metadata associated with them), the relationships between the items, in the context of a channel, haven’t been explored so much as it has been assumed.

Flipping Channels

The basic conceit of RSS is a channel. This is a term from information theory; the dictionary defines it as follows –
A course or pathway through which information is transmitted

This puts in more pressure on the changing nature of the information; it flows. Another often used term for an RSS channel is a feed,:

Feed is defined as the transmission or conveyance of a local radio or television program, as by satellite, on the Internet, or by broadcast over a network of stations

Thinking of an RSS channel as a flow is interesting for a number of reasons. Many RSS aggregators will keep a history of a channel and add to it over time, reconstructing the complete output of the flow. Some of them will also memorize the last snapshot of a flow that the user has seen.

More fundamentally, the flow nature of RSS needs to be aligned with that of the Web, as explained by Representational State Transfer (REST).

The Web according to REST is embodied by three components –

  • Identifiers (URIs)
  • Protocols (e.g., HTTP)
  • Formats (e.g., HTML; RSS, is a format as well).

Formats represent the state of a resource (as identified by a URI) in a snapshot (called a representation) that is sent using a Web protocol. But RSS is very often a partial snapshot; it describes the last few items in the feed, not the complete flow to date. Although other formats don’t always give the complete state of a resource.

A well-defined concept of a channel would allow other uses of RSS beyond simple headlines; aggregators could make more intelligent decisions about how to display a feed, enabling more content – from my Netflix queue to my Amazon shopping cart to a personal todo list.

As Weblogs repurposes RSS from headline syndication to their own purposes, so to can we find new applications of RSS, without sacrificing its legacy. Rather, if we explicitly state what’s implied about feeds now (reverse-chronological ordering), we enable new applications as well as new functionality for existing ones.

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