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[Bug 13465] Implement datatyping in Microdata

From: <bugzilla@jessica.w3.org>
Date: Mon, 01 Aug 2011 17:48:53 +0000
To: public-html-bugzilla@w3.org
Message-Id: <E1Qnwbl-0000kJ-1i@jessica.w3.org>
http://www.w3.org/Bugs/Public/show_bug.cgi?id=13465

Aryeh Gregor <Simetrical+w3cbug@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |Simetrical+w3cbug@gmail.com
         Resolution|                            |NEEDSINFO

--- Comment #2 from Aryeh Gregor <Simetrical+w3cbug@gmail.com> 2011-08-01 17:48:51 UTC ---
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Status: Additional Information Needed
Change Description: no spec change
Rationale:

I don't understand the use-cases.  In what circumstances would a microdata
consumer be able to make use of data type information, without any hardwired
information about the vocabulary?  If it does have hardwired information about
the vocabulary, why does data typing need to be part of the general syntax
instead of the vocabulary-specific semantics?  I looked at the use-cases that
microdata was written to cover and didn't see any where it would be useful:

http://wiki.whatwg.org/wiki/Microdata_Problem_Descriptions

(In reply to comment #0)
> 1. It's impossible to determine whether or not a value is an IRI, or a text
> string that looks like an IRI. This is an issue for forward-compatibility
> reasons, as a string intended to be a colon separated value today, e.g.
> dc:title, could be interpreted as a IRI tomorrow if a new scheme 'dc' were
> created. There is no deterministic way to understand the authors intent without
> datatyping in this case.

There is: specify it in the vocabulary, and assume that tools that consume the
data will be hardwired with vocabulary-specific information.

> 2. It is useful to applications to understand the datatype of a particular item
> in a machine-readable way. Asking application developers to create a universal
> way of figuring out what "45" means in a generic data processor is eased by
> tagging the value with a datatype. In one example, 'delta' could be expressed
> in "degrees Celcius, a unit of temperature measurement", in another "degrees, a
> unit of angle measurement".

What's a concrete example where this would be useful, as opposed to hardwiring
the units into the vocabulary?

> One suggestion is to create something in the Microdata spec that ensures that
> Web vocabularies are machine-readable and then set a "default type" for
> Microdata Web vocabularies. This would make it so that the complexity of
> datatyping is handled in the Web Vocabulary and does not have to be expressed
> by the Web author. Ideally, you would be able to specify a default type for Web
> Vocabulary terms as well as override that default type using something like
> @itemproptype.

Why can't the vocabulary require that a particular type always be used,
possibly a type that includes units in-band and therefore can accommodate
different units without extra metadata (e.g. "5km", "5mi", "5m")?

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Received on Monday, 1 August 2011 17:48:54 UTC

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