= Metadata =

== DFG Digitisation Guidelines ==

The "DFG Practical Guidelines on Digitisation" 
([http://www.dfg.de/forschungsfoerderung/wissenschaftliche_infrastruktur/lis/download/praxisregeln_digitalisierung.pdf German], [http://www.dfg.de/forschungsfoerderung/wissenschaftliche_infrastruktur/lis/download/praxisregeln_digitalisierung_en.pdf English]) discuss some metadata issues.

== Dublin Core ==

Dublin Core Metadata Initiative (links with a specified date point to a specific document verson, links without date point to the most recent version): 
  * [http://dublincore.org/ homepage], [http://dublincore.org/documents/ overview]
  * DCMI Metadata Terms: [http://dublincore.org/documents/dcmi-terms/ DCTERMS] (main document), [http://dublincore.org/usage/decisions/2008/dcterms-changes/ REVISIONS], [http://dublincore.org/documents/2008/01/14/domain-range/ DOMAINS]
  * DCMI Namespace Policy: [http://dublincore.org/documents/dcmi-namespace/ NAMESPACE]
  * DCMI Abstract Model: [http://dublincore.org/documents/2007/06/04/abstract-model/ DCAM] (aka ABSTRACT-MODEL)
  * DC and RDF: [http://dublincore.org/documents/dc-rdf/ DC-RDF], [http://dublincore.org/documents/dc-rdf-notes/ DC-RDF-NOTES]
  * DC and XML: [http://dublincore.org/documents/2003/04/02/dc-xml-guidelines/ 2003 XML Guidelines], may soon be superseded by the proposed recommendation [http://dublincore.org/documents/2008/09/01/dc-ds-xml/ 2008 XML Guidelines], [http://dublincore.org/documents/2008/09/01/dc-ds-xml-notes/ 2008 additional notes] (there is also a [http://dublincore.org/documents/dc-xml/ 2006 working draft])
  * [http://dublincore.org/tools/ software] (mainly online tools), [http://dublincore.org/resources/faq/ FAQ]

Some findings: Within the original 15 elements, {{{creator}}} now refines {{{contributor}}}, and {{{source}}} refines {{{relation}}} (i.e. searching for a contributor should also find a creator, etc.); one can still use {{{dc:}}} for the original 15 elements, but is encouraged to use {{{dcterms:}}} instead. {{{dcterms:date}}} has range {{{Literal}}}, {{{dcterms:language}}} has range {{{LinguisticSystem}}} ([http://dublincore.org/documents/dcmi-terms/ DCTERMS]). 
{{{DateScheme}}} and {{{LanguageScheme}}} were never officially declared and are no longer used; {{{ISO-639-3}}}, {{{W3CDTF}}} ([http://dublincore.org/usage/decisions/2008/dcterms-changes/ REVISIONS]).

[http://soap.stanford.edu/plugins/dublincore/ Dublin Core Metadata Generator] at Stanford.

== Metadata in our Schema ==

The [source:trunk/schema/schema/echo/modules/echo-metadata.rnc metadata module] in our Relax NG compact schema.

Some questions:

1. The definitions
{{{
dc.language = element dcterms:language { element rdf:Description { element dcq:languageScheme { "ISO 639-2" }, rdf.value } }
dc.date = element dcterms:date { element rdf:Description { element dcq:dateScheme { "ISO 8601" }, rdf.value } }
}}}
seem to be obsolete. Especially dcq seems obsolete (see [http://dublincore.org/documents/dcmi-namespace/ NAMESPACE]). I have replaced them by something which I believe is in accordance with Recommendation 7 in the [http://dublincore.org/documents/2003/04/02/dc-xml-guidelines/ 2003 XML Guidelines]:
{{{
dc.language = element dcterms:language { attribute xsi:type { "dcterms:ISO639-3" }, text }
dc.date = element dcterms:date { attribute xsi:type { "dcterms:W3CDTF" }, text } 
}}}
(Maybe I should have left {{{<rdf:value>}}} instead of "text"? But then, consequently ALL "text" in {{{dcterms}}} definitions should in fact be {{{<rdf:value>}}}.)

However, information is sparse. The syntax encoding schemes {{{dcterms:W3CDTF}}} and {{{dcterms:ISO639-3}}} do exist according to [http://dublincore.org/documents/dcmi-terms/ DCTERMS], but an up-to-date opinion about how to use syntax encoding schemes is difficult to obtain. The proposed recommendation [http://dublincore.org/documents/2008/09/01/dc-ds-xml/ 2008 XML Guidelines] uses {{{dcterm:date}}} only like this:
{{{
B.17:  <dcterms:date>2005-05-05</dcterms:date>
B.18:  <dcterms:date rdf:datatype="http://www.w3.org/2001/XMLSchema#date">2005-05-05</dcterms:date>
}}}

Each example in [http://dublincore.org/documents/2008/09/01/dc-ds-xml/ 2008 XML Guidelines] comes in three versions. The three versions of example 18 are:

DC-DS-XML (section 4.5.2.1):
{{{
<?xml version="1.0" encoding="UTF-8" ?>
<dcds:descriptionSet
  xmlns:dcds="http://purl.org/dc/xmlns/2008/09/01/dc-ds-xml/">
  <dcds:description
    dcds:resourceURI="http://dublincore.org/pages/home">
    <dcds:statement dcds:propertyURI="http://purl.org/dc/terms/title">
      <dcds:literalValueString>DCMI Home Page</dcds:literalValueString>
    </dcds:statement>
    <dcds:statement dcds:propertyURI="http://purl.org/dc/terms/publisher"
                   dcds:valueURI="http://example.org/agents/DCMI">
      <dcds:valueString>Dublin Core Metadata Initiative</dcds:valueString>
    </dcds:statement>
    <dcds:statement dcds:propertyURI="http://purl.org/dc/terms/date">
                       <!-- syntax encoding scheme URI -->
      <dcds:literalValueString dcds:sesURI="http://www.w3.org/2001/XMLSchema#date">2005-05-05</dcds:literalValueString>
    </dcds:statement>
  </dcds:description>
</dcds:descriptionSet>
}}}

DC-Text syntax (appendix A.18):
{{{
@prefix dcterms: <http://purl.org/dc/terms/> .
DescriptionSet (
  Description (
    ResourceURI ( <http://dublincore.org/pages/home> )
    Statement (
      PropertyURI ( dcterms:title )
      LiteralValueString ( "DCMI Home Page"
      )
    )
    Statement (
      PropertyURI ( dcterms:publisher )
      ValueURI ( <http://example.org/agents/DCMI> )
      ValueString ( "Dublin Core Metadata Initiative" )
    )
    Statement (
      PropertyURI ( dcterms:date )
      ValueString ( "2005-05-05"
        SyntaxEncodingSchemeURI ( <http://www.w3.org/2001/XMLSchema#date> )
      )
    )
  )
)
}}}

RDF/XML syntax (appendix B.18):
{{{
<?xml version="1.0" encoding="UTF-8" ?>
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
        xmlns:dcterms="http://purl.org/dc/terms/" >
  <rdf:Description rdf:about="http://dublincore.org/pages/home">
    <dcterms:title>DCMI Home Page</dcterms:title>
    <dcterms:publisher>
      <rdf:Description rdf:about="http://example.org/agents/DCMI">
        <rdf:value>Dublin Core Metadata Initiative</rdf:value>
      </rdf:Description>
    </dcterms:publisher>
    <dcterms:date rdf:datatype="http://www.w3.org/2001/XMLSchema#date">2005-05-05</dcterms:date>
  </rdf:Description>
</rdf:RDF>
}}}

Now what?

2. Should we rename our {{{<metadata>}}} element? In all examples it is {{{<ref:Description>}}}. However, in most examples it seems to mean the repository version of the metadata, not the version in the xml file itself.

3. Do we need something like {{{<foaf:Person>}}} for creators, contributors, etc.? (I guess not; it doesn't seem have any particular advantage.)