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Applying Postel's Law to HTML Data

From: Jeni Tennison <jeni@jenitennison.com>
Date: Wed, 5 Oct 2011 23:32:03 +0100
Message-Id: <408835CC-FF23-4F01-A159-A4240B2167A0@jenitennison.com>
To: public-html-data-tf@w3.org

Postel's law states [1]:

  "Be conservative in what you send; be liberal in what you accept."

To what extent does it make sense to have this as a guideline for HTML data? Should we recommend that consumers of data from HTML pages try to accept all data formats, and that publishers should publish in only one to simplify their markup?

There are a few examples where consumers are being liberal: Google Rich Snippets now uses both microdata and RDFa that uses the schema.org vocabulary [2], as well as various other vocabularies and microformats; Sindice [3] parses out RDFa, microdata and microformats. But there are also many examples of consumers and tools that are targeted towards one particular syntax -- I'm thinking of OGP from Facebook [4], various validators, browser plug-ins and Javascript libraries.

If consumers aren't liberal it's hard for publishers to be conservative. Should we encourage/anticipate people publishing in multiple formats with the same vocabulary to target different consumers? Publishing the same data in different vocabularies and different formats? Using different formats for different kinds of data or in different parts of the page?

What do you think?


[1]: http://en.wikipedia.org/wiki/Robustness_principle
[2]: http://www.google.com/webmasters/tools/richsnippets?url=http%3A%2F%2Fschema.openspring.net%2Fnode%2F3&view=cse
[3]: http://inspector.sindice.com/index.jsp
[4]: http://developers.facebook.com/docs/beta/opengraph/objects/
Jeni Tennison
Received on Wednesday, 5 October 2011 22:33:01 UTC

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