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Proposed update for Microdata to RDF specification

From: Gregg Kellogg <gregg@greggkellogg.net>
Date: Wed, 19 Nov 2014 08:54:37 -0800
Cc: W3C Web Schemas Task Force <public-vocabs@w3.org>
Message-Id: <343CA875-48ED-4862-BC8F-9FDAD5118864@greggkellogg.net>
To: "semantic-web@w3.org Web" <semantic-web@w3.org>
Based on feedback and emerging requirements, I’ve prepared another draft for an update to the Microdata to RDF Note [1]. As this is a Note of the Semantic Web Interest Group, please send feedback to semantic-web@w3.org. This update represents a substantial simplification to the algorithm by eliminating unused mechanisms and simplifies generation of implied triples (e.g. schema:additionalType).

This Working Draft is an update of the W3C Interest Group Note, published in October 2012. This update simplifies processing using the following mechanisms:

• Experimental support for @itemprop-reverse has been added. This attribute is not part of [MICRODATA] and is included as an experimental feature. Specific feedback from the community is requested. Based on addoption, the attribute may be considered for inclusion in forthcoming versions of [MICRODATA] and this note. (see issue 5 [2])

• Top-level items were previously included in a md:item RDF Collection to reconstruct the order that items appear in the DOM. This has also proven to not be useful and has been dropped. (see issue 6 [3])

• A property value may be extracted from the @content attribute of the meta element. (see issue 7 [4])

• A property value may be extracted from the @value attribute of the data or meter elements. If this value has numeric form, it will produce a datatyped literal using the appropriate datatype from [XMLSCHEMA11-2] (see issue 8 [5] and issue 9 [6])

• Property URI generation was under control of the propertyURI registry setting. This setting could previously have taken either the _vocabulary_ or _contextual_ settings. As _contextual_ was never used in a registry, and usage in the wild favors the vocabulary setting, support for _contextua_l has been eliminated, and consequently support for the propertyURI element within the registry. This issue remains open pending community review; specifically, anyone depending on this feature should provide feedback as requested below. (see issue 10 [7])

• An item having multiple values for a given property could previously having been placed in an RDF Collection if the multipleValues registry setting were set to _list_. Although the previous registry did have such a setting for some schema.org values, this is not honored by most search engines, and so has been dropped, and consequently support for the multipeValues element within the registry. This issue remains open pending community review; specifically, anyone depending on this feature should provide feedback as requested below. (see issue 10 [7])

• Lastly, the previous update introduced Vocabulary Expansion using entailment rules adopted from [RDFA-CORE] under control of the vocab_expansion option. Support for Vocabulary Expansion has been substantially simplified, and is no longer under control of an option. This issue remains open pending community review; specifically, anyone depending on this feature should provide feedback as requested below. (see issue 10 [7])

The intention is to publish this draft as a new version of the Interest Group Note after gathering and incorporating community input. Please provide feedback by 5 December 2014. Please see GitHub issues for a discussion of tradeoffs considered in this version.

An updated test suite is referenced from the spec. A diff to the previous revision is available using the ReSpec key-sequence SHIFT-CTRL-ALT-S when viewing the spec.

Gregg Kellogg
gregg@greggkellogg.net

[1] http://w3c.github.io/microdata-rdf
[2] https://github.com/w3c/microdata-rdf/issues/5
[3] https://github.com/w3c/microdata-rdf/issues/6
[4] https://github.com/w3c/microdata-rdf/issues/7
[5]https://github.com/w3c/microdata-rdf/issues/8
[6] https://github.com/w3c/microdata-rdf/issues/9
[7] https://github.com/w3c/microdata-rdf/issues/10
Received on Wednesday, 19 November 2014 16:55:04 UTC

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