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Subject:

Re: Guidance on DC Schema extensibility

From:

"Retter, Adam" <[log in to unmask]>

Reply-To:

Retter, Adam

Date:

Mon, 17 Oct 2011 14:08:27 +0100

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (296 lines)

Hans,



Firstly thanks for the reply :-)



I did consider creating a Dublin Core Application profile, however this seemed like a huge amount of work and I had to take the pragmatic route that I probably only have several days to achieve results that can be used for implementation.

Our metadata requirements at the moment are entirely internal, as such I have created a small set of guide documents which describe the DCMI terms that should be applied to what and when, I imagine that this could later be used as the basis for a full Dublin Core Application Profile.



I am REALLY looking for guidance on how this should be expressed in XML and XML Schema as per my examples, I did take a look at your XML expressions, but these only use simple string values and describe how these should be expressed. Rather I am looking to use complex XML snippets as the values of my Dublin Core terms. I wonder if you don't do this, because it is not an appropriate thing to do? Do you have contact with those that defined your XML Schemas for this, perhaps they could comment?





Cheers Adam.



-----Original Message-----

From: Hans Overbeek [mailto:[log in to unmask]] 

Sent: 17 October 2011 13:10

To: Retter, Adam; [log in to unmask]; DCMI Government Community

Subject: RE: Guidance on DC Schema extensibility



Hi Adam,



For ther Dutch government we developed a Dublin Core Application profile which we use again as an intermediate standard between Dublin Core specifications and the specific application standards. The standard is called OWMS (Overheid.nl Web Metadata Standard. 'Overheid' means 'Government'). It is published in Dutch at [1] but wit Google translate [2] you should get a picture. The only documentation in english is a technical review of OWMS 3.5 in 2008 [8].



Important in our case is of course the translation of the DC-terms into Dutch, but we also narrow down the semantics of the DC terms a little bit to the government domain and our needs. For instance, we define our own core-properties: A set of 9 properties that are mandatory if applicable. This encourages implementing parties to use the standard.

We also defined a namespace 'overheid' ('government') to hold terms that can be used in many applications. In this namespace we defined a new property 'overheid:authority' [3] with semantics that we need in a government context and which are not covered by the Dublin Core terms.

The 'overheid:authority' is the governmental organisation that is to be held legally responsible for the content (meaning) of the information object. This is often, but not necessarily, the same organisation as the creator.



The namespace also contains some lists of values that can be used to specify the properties [4]. So for instance, we publish lists with government organisations and a list with information types.





We than created a technical framework that allowed others to define their own application profile on top of our specifications. The framework enforces that the nine core properties are used, it supports re-use of our lists of values and other Dublin Core properties, and it allowes to extend the scheme with application specific properties and lists of value.



The framework consists of a set of XSD's [5] and supported by Schematron rules to perform the look-up of the lists of values.



We tried out two approaches: OWMS full and OWMS plugin.

The OWMS full approach provides for a template XSD that can be extended for your own needs.

The OWMS plugin XSD's can be plugged into an existing XSD. It is more flexible to apply, but it is less strict with respect to the constraints we can enforce.





RE: dcterms:spatial [6] we only support postal code/house number and organisation, where the latter has to be explained as the mandated territory of the organisation mentioned. This was not enough for some application profiles, so they worked their way around it. se for example the application profile (or content model as we call it) for permits.

[7] My knowledge of XML is too poor to give detailed feedback on your examples, sorry.



In practice we see that simplicity usually wins from completeness. So people prefer pragmatic sollutions and accept it does 'only' 80-90 % of the job. We therefor aim at future use of URI's from the National Geo Registers that are under development right now, rather than developing structures to specify literal values right now. 





These are interesting challenges we are facing. And I'm sure we are looking at the comparable problems in many countries. Therefor I also post my response to th DC-Government list where we discuss these kind of problems and solutions in a government context.



All,

Please share your views!





[1] http://standaarden.overheid.nl/owms/

[2]

http://translate.google.com/translate?hl=nl&sl=auto&tl=en&u=http%3A%2F%2

Fstandaarden.overheid.nl%2Fowms%2F



[3] nl

http://standaarden.overheid.nl/owms/4.0/doc/eigenschappen/overheid.autho

rity.html

[3] en

http://translate.google.com/translate?hl=nl&sl=auto&tl=en&u=http%3A%2F%2

Fstandaarden.overheid.nl%2Fowms%2F4.0%2Fdoc%2Feigenschappen%2Foverheid.a

uthority.html



[4] nl http://standaarden.overheid.nl/owms/4.0/doc/waardelijsten/

[4] en

http://translate.google.com/translate?hl=nl&sl=auto&tl=en&u=http%3A%2F%2

Fstandaarden.overheid.nl%2Fowms%2F4.0%2Fdoc%2Fwaardelijsten%2F



[5] nl http://standaarden.overheid.nl/owms/4.0/schemas4.0.html

[5] en

http://translate.google.com/translate?hl=nl&sl=auto&tl=en&u=http%3A%2F%2

Fstandaarden.overheid.nl%2Fowms%2F4.0%2Fschemas4.0.html



[6] nl

http://standaarden.overheid.nl/owms/4.0/doc/eigenschappen/dcterms.spatia

l.html

[6] en

http://translate.google.com/translate?hl=nl&sl=auto&tl=en&u=http%3A%2F%2

Fstandaarden.overheid.nl%2Fowms%2F4.0%2Fdoc%2Feigenschappen%2Fdcterms.sp

atial.html





[7] nl http://standaarden.overheid.nl/vergunningen/

[7] en

http://translate.google.com/translate?hl=nl&sl=auto&tl=en&u=http%3A%2F%2

Fstandaarden.overheid.nl%2Fvergunningen%2F



[8] en

http://www.e-overheidvoorburgers.nl/binaries/overheidheeftantwoord/pdf/m

etadata/owms_final_report_20081212.pdf



With kind regards,

Hans Overbeek

Consultant Content Standards



e-Overheid voor Burgers 





ICTU

Wilhelmina van Pruisenweg 104, 2595 AN Den Haag Postbus 84011, 2508 AA Den Haag Tel. +31-6-1830 7858, Secretariaat 070 - 888 78 50

E-mail: [log in to unmask]

Internet: www.e-overheidvoorburgers.nl

http://www.overheid.nl

http://mijn.overheid.nl

http://standaarden.overheid.nl

http://data.overheid.nl 







> -----Oorspronkelijk bericht-----

> Van: General DCMI discussion list

> [mailto:[log in to unmask]] Namens Retter, Adam

> Verzonden: maandag 17 oktober 2011 11:05

> Aan: [log in to unmask]

> Onderwerp: Guidance on DC Schema extensibility

> 

> Hi there,

> 

> I am looking for some advice on best practice of refining/extending 

> Dublin Core, specifically we are constrained by XML Schema and so RDF 

> options are not possible. My position here is to create an XML Schema 

> that holds metadata about resources and processes. I feel that it is 

> important to reuse existing standards where possible rather than 

> inventing the wheel again, as such I am looking to the DCMI Metadata 

> Terms.

> 

> Some existing DCMI Metadata Terms are a natural fit for this, e.g. 

> title, language, publisher. However, others lack the precision 

> semantics that we need, I have identified two possible ways in which 

> we could incorporate this precision with Dublin Core, but am unsure of 

> the best approach and would appreciate some advice from the Dublin 

> Core perspective.

> 

> Consider for example dcterms:spatial, a simple literal value is not 

> enough for us, we need a complex addressing mechanism -

> 

> Approach 1, make use of xsi:type by extending dc:SimpleLiteral -

> 

> Example XML -

> <dcterms:spatial xsi:type="m:address">

> 	<m:address-line>102</m:address-line>

> 	<m:address-line>Some Road</m:address-line>

> 	<m:settlement xsi:type="dcterms:TGN">York</m:settlement>

> 	<m:county>Yorkshire</m:county>

> 	<m:country>GB</m:country>

> </dcterms:spatial>

> 

> Example XML Schema snippet for 'm' -

> <xs:complexType name="address">

>     <xs:annotation>

>         <xs:documentation xml:lang="eng">Restriction of the spatial 

> coverage for use in Dublin Core's dc:spatial e.g. The geographical 

> area/address represented</xs:documentation>

>     </xs:annotation>

>     <xs:complexContent mixed="true">

>         <xs:extension base="dc:SimpleLiteral">

>             <xs:sequence>

>                 <xs:choice maxOccurs="unbounded">

>                     <xs:element name="address-line" 

> type="xs:string" maxOccurs="unbounded"/>

>                     <xs:element name="settlement" type="xs:string">

>                         <xs:annotation>

>                             <xs:documentation>Should consider 

> restricting values to a controlled vocabularly such as Getty TGN 

> through xsi:type="dcterms:TGN"</xs:documentation>

>                             <xs:appinfo>

>                                 

> <dcterms:hasFormat>http://purl.org/dc/terms/#ves-TGN</dcterms:

> hasFormat>

>                             </xs:appinfo>

>                         </xs:annotation>

>                     </xs:element>

>                     <xs:element name="county" type="xs:string">

>                         <xs:annotation>

>                             <xs:documentation>Should consider 

> restricting values to a controlled vocabularly such as Getty TGN 

> through xsi:type="dcterms:TGN"</xs:documentation>

>                             <xs:appinfo>

>                                 

> <dcterms:hasFormat>http://purl.org/dc/terms/#ves-TGN</dcterms:

> hasFormat>

>                             </xs:appinfo>

>                         </xs:annotation>

>                     </xs:element>

>                     <xs:element name="country" 

> type="stl:ISO3166CountyCode"/>

>                     <xs:element name="postal-code" type="xs:string"/>

>                 </xs:choice>

>             </xs:sequence>

>         </xs:extension>

>     </xs:complexContent>

> </xs:complexType>

> 

> 

> Approach 2, make use of substitution groups -

> 

> Example XML -

> <m:address>

> 	<m:address-line>102</m:address-line>

> 	<m:address-line>Some Road</m:address-line>

> 	<m:settlement>York</m:settlement>

> 	<m:county>Yorkshire</m:county>

> 	<m:country>GB</m:country>

> </m:address>

> 

> Example XML Schema for 'm' -

> <xs:element name="address" type="addressType" 

> substitutionGroup="dcterms:spatial"/>    

> <xs:complexType name="addressType">

>     <xs:sequence>

>         <xs:choice maxOccurs="unbounded">

>             <xs:element name="address-line" type="xs:string" 

> maxOccurs="unbounded"/>

>             <xs:element name="settlement" type="xs:string">

>                 <xs:annotation>

>                     <xs:documentation>Should consider restricting 

> values to a controlled vocabularly such as Getty TGN through 

> xsi:type="dcterms:TGN"</xs:documentation>

>                     <xs:appinfo>

>                         

> <dcterms:hasFormat>http://purl.org/dc/terms/#ves-TGN</dcterms:

> hasFormat>

>                     </xs:appinfo>

>                 </xs:annotation>

>             </xs:element>

>             <xs:element name="county" type="xs:string">

>                 <xs:annotation>

>                     <xs:documentation>Should consider restricting 

> values to a controlled vocabularly such as Getty TGN through 

> xsi:type="dcterms:TGN"</xs:documentation>

>                     <xs:appinfo>

>                         

> <dcterms:hasFormat>http://purl.org/dc/terms/#ves-TGN</dcterms:

> hasFormat>

>                     </xs:appinfo>

>                 </xs:annotation>

>             </xs:element>

>             <xs:element name="country" type="stl:ISO3166CountyCode"/>

>             <xs:element name="postal-code" type="xs:string"/>

>         </xs:choice>

>     </xs:sequence>

> </xs:complexType>

> 

> 

> My feeling is that the first approach is the preferred mechanism as 

> when you look at or process the metadata it is absolutely explicit 

> that this is a dcterms:spatial, and if you received this document as a 

> 3rd party then as a minimum you were just able to extract the text 

> nodes, you would have a strict dcterms compliant spatial property.

> One downside to this is that we have to sprinkle xsi:type attribute 

> annotations into our XML instances. However there is also an advantage 

> to this, which is that in future if we have values that we have 

> non-anticipated we can simply create new complexTypes for refinement, 

> or even default to the lowest common denominator i.e. dc:SimpleLiteral 

> which is just an xs:string.

> 

> I would appreciate thoughts on this from the Dublin Core perspective, 

> how have others done this in the past, what is the recommended best 

> practice?

> 

> 

> Thanks Adam

> 

> Please don't print this e-mail unless you really need to.

> 

> --------------------------------------------------------------

> -------------------

> 

> National Archives Disclaimer

>  

> This email message (and attachments) may contain information that is 

> confidential to The National Archives. If you are not the intended 

> recipient you cannot use, distribute or copy the message or 

> attachments. In such a case, please notify the sender by return email 

> immediately and erase all copies of the message and attachments. 

> Opinions, conclusions and other information in this message and 

> attachments that do not relate to the official business of The 

> National Archives are neither given nor endorsed by it.

> 

> --------------------------------------------------------------

> ----------------------

> 

> 



Please don't print this e-mail unless you really need to.



---------------------------------------------------------------------------------



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This email message (and attachments) may contain information that is confidential to The National Archives. If you are not the intended recipient you cannot use, distribute or copy the message 

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