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Re: "scheme" attribute of META element

From: Tom Dent <tom.dent@porism.com>
Date: Tue, 4 Aug 2009 07:43:39 +0100
Message-ID: <9e02d7200908032343j2e86ebadpa9b5e5285a22b949@mail.gmail.com>
To: Ian Hickson <ian@hixie.ch>
Cc: public-html-comments@w3.org
On Wed, Jul 29, 2009 at 7:27 PM, Ian Hickson <ian@hixie.ch> wrote:
>
> On Wed, 29 Jul 2009, Tom Dent wrote:
> >
> > As well as using Dublin Core, other schemes are used, such as IPSV
> > (Integrated Public Sector Vocabulary): '<meta name="DC.subject"
> > scheme="eGMS.IPSV" content="Youth centres"/>'. IPSV is a controlled list
> > that was developed with the backing of the Department for Communities and
> > Local Government (CLG - formerly the Office of the Deputy Prime Minister)
> > and the e-Government Unit (e-GU) of the Cabinet Office for use by UK
> > public sector organisations and is available in machine-readable format
> > from here: http://www.esd.org.uk/standards/ipsv/
>
> What other scemes are used with this name?
I'm not sure what you mean, but any controlled list (eGMS also
references the Local Government Service List (available at
http://www.esd.org.uk/standards/lgsl)) or data format pattern might
constitute a scheme. The Dublin Core metadata, which is also
referenced, is designed to be universal, as are the schemes which it
employs (such as date and URI), and references other more universal
schemes such as ISO 3166 http://www.iso.org/iso/country_codes.htm

> What happens when the value used doesn't come from the allowed list? Or
> when the scheme doesn't match "eGMS.IPSV" but the value is still one of
> the allowed values?
If a value does not reflect a concept id or preferred label for a
concept in a controlled list, the page reference is ignored as
invalid.  If the value is an allowed value but the scheme is not
specified, we assume that the value does not necessarily mean the same
as we mean within the scheme.  Hence again we ignore the reference.
So we could think of the scheme as a namespace for the value.

> > Due to the fact that IPSV uses a controlled set of terms, these pages can
> > be referenced in a way which is relatively easy for a machine to
> > reference, as the scheme gives the name of the list to be used and the
> > content gives the name of the item, making it a more reliable way of
> > sourcing the exact content of the page and matching it to others that are
> > used. The extent of its use means that Sitemorse, a company who check page
> > validity of UK sites in several areas, use this metadata to check content:
> > http://www.sitemorse.com/kb.html?kb=1266176694 and it is a feature built
> > into a CMS used by UK sites:
> > http://www.jadu.co.uk/info/20029/government/45/integrated_public_sector_vocabulary_ipsv/1
>
> Could you show an example of how the scheme attribute affects the user
> experience? I looked around but couldn't find any pages that actually
> expose any of this data, so it wasn't clear to me whether any code other
> than the validators and CMSes actually used it.
The scheme does not directly impact on the user, but can (for example)
do so via search software.  You can see a view of IPSV at
http://www.esd.org.uk/standards/ipsv/viewer/ or LGSL at
http://www.esd.org.uk/standards/lgsl/viewer .

If a user searched for pages by using a "non-preferred term", the
search engine should convert that to an IPSV preferred term and then
return all content with that preferred term in its metadata (with the
IPSV scheme).  The search software might also suggest showing content
for broader and narrower subject headings from the IPSV hierarchy.

The LGSL is being used to reference local authority sites in the UK
Government's Directgov site (at http://www.direct.gov.uk/) which is
used as a portal to local authority sites, and uses LGSL to reference
pages.

Tom Dent
Porism Limited
tom.dent@porism.com
Received on Tuesday, 4 August 2009 06:44:22 GMT

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