[Zope-CMF] Re: Metadata Toolz

[Tres Seaver]

On Thu, 2002-10-10 at 05:54, Erik Lange wrote:
> At 09:41 AM 10/10/02, Paul Everitt wrote:
> 
> >On lundi, oct 7, 2002, at 15:06 Europe/Paris, Gitte Wange wrote:
> >
> >>Well I have been thinking about it all morning :-)
> >>I was thinking about doing something to the metadata tool so it could
> >>use different metadata implementations (specify them through ZMI). In
> >>that order you could say that your Images should use DublinCore metadata
> >>but your media events should use MPEG-7 ... :-)
> >>Sort of like with the workflow tool ... I think :-))
> >
> >I'll give fair warning here...if nobody participates in Z3WCM (Zope 3 Web 
> >Content Management), then its metadata *might* look the way I lobby for, 
> >and that means:
> >
> >1) There are core metadata items that all "content" must provide for (even 
> >if there are no values).
> 
> Yes.
> 
> 
> >2) That core metadata model is spelled d-u-b-l-i-n c-o-r-e. :^)
> 
> The core DublinCore-implementation, should then have _all_ elements from 
> dublin core implemented - even if they are left blank for no values and 
> maybe are not even shown on the default layer-implementation forms.
> 
> I.e. has.part and is.part.of has been mentioned as "missing" in the current 
> DC-implementation... I believe it will only add to the confussion, if there 
> is a "light-DC-implementation" and a "full-DC-implementation" for the Z3Core...
> 
> >Of course the metadata model should be extensible.
> 
> :-)
> 
> >I'm still confused by the problem, though...is the stuff in media events 
> >data or metadata?
> 
> The data we need to describe with metadata in a media event, is data that 
> is described not only by title, description, URI, etc., etc. - but that is 
> also described by a time indication on where _within_ a given datafile, the 
> given data-segment can be found.
> 
> I.e. you need to define start-time and end-time to define a certain clip in 
> a movie... that's why dublin core, even with all elements implemented, 
> can't describe our resources "correct". For that we need to extend the 
> metadata namespace we use, whit a namespace that handles time-indications.
> 
> This extension can be defined with dublin core, so dublin core should - 
> IMHO - always be the base of all metadata.

No, I don't think so.  DC should be the "lingua franca" schema onto
which other schemas can be mapped, with loss of fidelity.  It is *not*
the Right Thing (TM) for all cases.

> Dublin core's "has.part" and "is.part.of" elements, will make it possible 
> to describe wich clips are related to which physical datafiles and vice versa.

Those aren't elements;  they are qualifiers on the Relation element:

  http://www.dublincore.org/documents/dces/#relation

  http://www.dublincore.org/documents/dcmes-qualifiers/#relation

DC also has a (redundant) Source element (Source is nothing more than a
special, qualified Relation, where the qualifier would be 'Derives
From', or some such).

Right now, content in the CMF doesn't know about the Relation element,
because unlike the other elements it is *complicated*;  it essentially
*requires* qualifiers (like Date) in order to make sense.  A sane
implementation is also likely to require something like Ken Manheimer's
"organization objects" proposal, at least if relations are based on
anything other than pure containment.

Steps to move forward for the CMF (Zope 3 is already there, really,
given the work so far on implementing DublinCore via IAnnotation et
aliae):

 - Refactoring the current "default" DC implementation to indirect
   knowledge of metadata storage through the 'portal_metadata' tool
   (this is an essential first step to almost *any* metadata changes).

 - Modifying the tool to store all "simple" DC elements on a
   separate propertysheet (instead of as direct attributes on the
   content object).

 - Extending the tool to support qualifiers on elements.

 - Extending the tool to support currently-unsupported elements,
   including Relation, with appropriate semantics.

Anyone want to sign up?

Tres.
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Tres Seaver                                tseaver@zope.com
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