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Re: RDF Lang tagged literals Re: vCard Update

From: Richard Cyganiak <richard@cyganiak.de>
Date: Sat, 20 Oct 2012 14:40:43 +0200
Cc: Semantic Web <semantic-web@w3.org>
Message-Id: <7B7F062B-33FF-46C6-AE1B-A14983C8685C@cyganiak.de>
To: Ivan Herman <ivan@w3.org>, Dave Reynolds <dave.e.reynolds@gmail.com>
On 19 Oct 2012, at 12:34, Ivan Herman wrote:
> On 19 Oct 2012, at 03:27, Dave Reynolds <dave.e.reynolds@gmail.com> wrote:
>>> just a thought... I know we have a timing issue here, but maybe it is worth thinking ahead (e.g., republishing a note later) with an eye on RDF 1.1 that should be finalized sometimes in 2012. One of the few changes in RDF 1.1 is the handling of language and plain literals:
>>> 
>>> http://dvcs.w3.org/hg/rdf/raw-file/default/rdf-concepts/index.html#section-Graph-Literal
>> 
>> Hmmm. Is there a write up somewhere of how the transition is supposed to work?
> 
> Not at this moment, unless Richard knows something I do not.

No, there's no such writeup. I'll raise this as an issue in RDF-WG.

A short summary:

- This is a change to the RDF data model (the abstract syntax)
- Nothing changes in RDF syntaxes (Turtle, RDF/XML) as a result, and no published data has to be changed
- Other access interfaces (query languages, APIs) will change behaviour in some cases as they migrate to 1.1
- In RDF 1.1, they *must* treat untagged plain literals and xsd:string as the same
- Query languages and APIs of course remain free to define how exactly they bind to the data model
- Therefore, such query languages and APIs need to choose whether to report the datatype of such literals as “none” or as “xsd:string” (with the second being a better choice, IMO)
- Query languages and APIs also need to choose whether to report the datatype of language-tagged plain literals as “none” or as “rdf:langString” (SPARQL 1.1 already does the latter)
- I expect that RDF stores will have an option to upgrade a store to RDF 1.1; this option would go through the stored data and unify xsd:string literals and untagged plain literals
- I expect a long transition phase where RDF APIs will have a switch where they can be run in one of two modes, with “RDF 1.0 mode” being the current behaviour, and “RDF 1.1 mode” activating different behaviour as outlined above. Application developers may need to modify some queries before they can switch from 1.0 mode to 1.1 mode

There's more to be said about XML literals, the new HTML literals, and the introduction of named graphs into the core data model.

Best,
Richard
Received on Saturday, 20 October 2012 17:05:26 UTC

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