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Expressing Dublin Core metadata using XML (DC-XML-Min)

This document is part of the DC Architecture Wiki.

IMPORTANT: Do not cite materials in this Wiki other than for the purposes of collaborating on document creation. This Wiki is intended to be used to work on draft copies of documents. Finished documents will be published, in a persistent and citable form, on the dublincore.org Web site (or elsewhere in some cases).

Contents

1. Introduction

2. The DCMI Abstract Model and DC-XML-Min

3. The DC-XML-Min Syntax

4. GRDDL

5. Appendix A: Text Representation of Examples

6. Notes

7. References

1. Introduction

This document specifies an XML format for representing a DC metadata description set. The XML format is known as "DC-XML-Min".

The DCMI Abstract Model [DCAM] describes the constructs that make up a DC metadata description set. In order to represent a DC metadata description set in an XML document those constructs have to be represented as components in that XML document, i.e. as XML elements and XML attributes, XML element names and XML attribute names, and as XML element content and XML attribute values.

1.1 Design Considerations

The DC-XML-Min format described in this document was developed using the following design considerations:

• The format should provide a serialisation of a subset of the features of the "Description Model" of the DCAM, i.e. it should be possible to represent a well-defined subset of the constructs that make up a DC metadata description set. Some DC metadata description sets have no corresponding representation in this XML format. (See Note 1).

• The format is not required to address the features of the "Schema Model" of the DCAM. For example, it is not required to express subproperty relationships between properties, subclass relationships between classes, etc.

• The format should be easily usable with XML-based specifications such as XPath, XPointer and XQuery, i.e. for each construct in the DCAM there should be a mapping to exactly one construct in the XML syntax.

• The format should not be dependent on features of a single XML Schema language.

• It should be possible to describe the format using W3C XML Schema [XMLSCHEMA], but it is not a requirement that when the format is used to serialise description sets conforming to a DC Application Profile, all the constraints expressed in a DC Application Profile are captured using W3C XML Schema.

2. The DCMI Abstract Model and DC-XML-Min

According to the DCAM description model:

• a description set is made up of one or more descriptions

• a description is made up of

• zero or one resource URI and

• one or more statements

• a statement is made up of

• exactly one property URI and

• zero or one reference to a value in the form of a value URI

• zero or more representations of a value, each in the form of a value representation

• zero or one vocabulary encoding scheme URI

• zero or one value class URI

• a value representation is either

• a value string or

• a rich representation

• a value string may be associated with either a value string language or a syntax encoding scheme URI

• a value may be the described resource of another description in the description set

The DC-XML-Min format described in this document implements the following subset of the features of the DCAM description model:

• a description set is made up of one or more descriptions

• a description is made up of

• zero or one resource URI and

• one or more statements

• a statement is made up of

• exactly one property URI and

• zero or one reference to a value in the form of a value URI

• zero or one representation of a value in the form of a value string

• zero or one vocabulary encoding scheme URI

• zero or one value class URI

• a value string may be associated with either a value string language or a syntax encoding scheme URI

• a value may be the described resource of another description in the description set

i.e. the DC-XML-Min format supports a maximum of one value representation per statement and that value representation must be in the form of a value string. Rich representations are not supported.

3. The DC-XML-Min Syntax

3.1 URIs in DC-XML-Min

The DCAM uses Uniform Resource Identifiers (URIs) [RFC3896] to refer both to resources and to metadata terms (properties,classes, vocabulary encoding schemes and syntax encoding schemes).

In DC-XML-Min, some URIs in a DC metadata description set are encoded as URI references in XML attribute values, and some URIs are represented as XML Qualified Names (QNames). Note that only some URIs are represented as XML QNames. The table below summarises the options available:

Later sections of this document describe the encoding of the different URIs in detail. The purpose of this section is to make some general points about the representation of URIs in DC-XML-Min.

3.1.1 URI references

In DC-XML-Min, some URIs are encoded as URI references, used as XML attribute values. A URI reference is either a URI or a relative reference [RFC3896].

The URI may be represented in full. The following example shows a URI as the value of the dcxm:resourceURI attribute:

<?xml version="1.0"?>
<dcxm:descriptionSet 
  xmlns:dcxm="http://dublincore.org/xml/dc-xml-min/2006/09/18/"
  xmlns:dc="http://purl.org/dc/elements/1.1/">
  <dcxm:description
    dcxm:resourceURI="http://dublincore.org/pages/home"> <!-- Resource URI -->
    <dc:title>DCMI Home Page</dc:title>
  </dcx:description>
</dcxm:descriptionSet>

XML Example 1: URI as attribute value

The representation of the URI may be abbreviated through the use of an XML entity reference as follows, for example:

<?xml version="1.0"?>
<!DOCTYPE dcxm:descriptionSet [
  <!ENTITY dcmi 'http://dublincore.org/pages/'>
]>
<dcxm:descriptionSet 
  xmlns:dcxm="http://dublincore.org/xml/dc-xml-min/2006/09/18/"
  xmlns:dc="http://purl.org/dc/elements/1.1/">
  <dcxm:description
    dcxm:resourceURI="&dcmi;home"> <!-- Resource URI using XML entity reference -->
    <dc:title>DCMI Home Page</dc:title>
  </dcx:description>
</dcxm:descriptionSet>

XML Example 2: URI as attribute value (with XML entity reference)

For all of the attributes in DC-XML-Min which have URIs as values, the value may also be a relative reference. The relative reference is resolved relative to a base URI, obtained either from the value of an xml:base attribute or from the URI of the document itself. In the following example, the value of the dcxm:resourceURI attribute is a relative reference. It is resolved relative to the base URI provided by the xml:base attribute to obtain a target URI of http://dublincore.org/pages/home:

<?xml version="1.0"?>
<dcxm:descriptionSet 
  xml:base="http://dublincore.org/pages/"
  xmlns:dcxm="http://dublincore.org/xml/dc-xml-min/2006/09/18/"
  xmlns:dc="http://purl.org/dc/elements/1.1/">
  <dcxm:description
    dcxm:resourceURI="home"> <!-- Resource URI as relative reference -->
    <dc:title>DCMI Home Page</dc:title>
  </dcx:description>
</dcxm:descriptionSet>

XML Example 3: Relative reference as attribute value

3.1.2 URIs and XML QNames

In DC-XML-Min, some URIs are represented as XML Qualified Names (QNames). An XML QName is an abbreviation for an "expanded name", a pair consisting of an XML Namespace Name (a URI) and a local name. The prefix part of the XML QName is bound to an XML Namespace Name through an XML Namespace declaration; where an XML QName has no prefix, the XML Namespace Name is obtained from the default namespace declaration.

For a software application that is parsing a DC-XML-Min instance to construct a description set, where an XML QName is used to represent a URI, the URI is determined by appending the local name part of the QName to the XML Namespace Name. Note that only some XML QNames in a DC-XML-Min instance are mapped to URIs in this way: this specification indicates when that mapping is applied.

For a software application that is "encoding" a description set by generating a DC-XML-Min instance, an XML QName is determined by

• dividing the URI into a pair consisting of a local name (the trailing characters of the URI, subject to the lexical constraints of the QName datatype) and a URI to be used as an XML Namespace Name (the preceding part of the URI),

• providing an XML Namespace declaration element for this XML Namespace Name, and

• deploying an XML QName using the local name and the prefix used in the namespace declaration (or omitting the prefix if a default namespace declaration was used).

Note that this means for a single URI there is more than one possible DC-XML-Min Qualified Name representation. For example, the URI http://purl.org/dc/elements/1.1/date might be represented using any of the following (XML Namespace Name, local name) pairs:

• {http://purl.org/dc/elements/1.1/}, date

• {http://purl.org/dc/elements/1.1/d}, ate

• {http://purl.org/dc/elements/1.1/da}, te

• {http://purl.org/dc/elements/1.1/dat}, e

Communities typically decide on a convention for the QName to be used, but in theory any of these four forms could be deployed without changing the interpretation of the instance. For all DCMI terms, the convention used by the DCMI community is to split the term URI into an expanded name at the right-most '/' (forward slash) character (as per the first example above).

In the three examples in section 3.1.1 above, the XML QName dc:title is used to represent the property URI http://purl.org/dc/elements/1.1/title.

3.2 Encoding a Description Set: The Description Set Element

A description set is a set of one or more descriptions.

In DC-XML-Min, a description set is represented by an XML element known as a Description Set Element (See Note 2). A DC-XML-Min instance represents a single DC description set, so has exactly one Description Set Element.

A Description Set Element has an expanded name (XML Namespace Name/local name pair) with the XML Namespace Name http://dublincore.org/xml/dc-xml-min/2006/09/18/ and local name descriptionSet.

In the examples presented in this document, the XML Namespace Name http://dublincore.org/xml/dc-xml-min/2006/09/18/ is always associated with the prefix "dcxm". For convenience, after this point, the names of XML elements and XML attributes are presented in the text as XML QNames (e.g. dcxm:descriptionSet, dcxm:resourceURI), rather than as expanded names, but the prefix used is not significant.

<?xml version="1.0"?>
       <!-- Description Set Element -->
<dcxm:descriptionSet 
  xmlns:dcxm="http://dublincore.org/xml/dc-xml-min/2006/09/18/"
  xmlns:dc="http://purl.org/dc/elements/1.1/">
  <dcxm:description>
    <dc:title>DCMI Home Page</dc:title>
  </dcxm:description>
</dcxm:descriptionSet>

XML Example 4: The Description Set Element

A Description Set Element contains one or more Description Elements.

3.3 Encoding a Description: The Description Element

A description is a set of one or more statements about a resource.

In DC-XML-Min, a description is represented by an XML element known as a Description Element. Any XML element which is a child element of a Description Set Element is a Description Element.

The following example shows a description set consisting of a single description:

<?xml version="1.0"?>
<dcxm:descriptionSet
  xmlns:dcxm="http://dublincore.org/xml/dc-xml-min/2006/09/18/"
  xmlns:dc="http://purl.org/dc/elements/1.1/"
  xmlns:my="http:example.org/myapplication/">
  <my:webPageDescription> <!-- Description Element -->
    <dc:title>DCMI Home Page</dc:title>
  </my:webPageDescription>
</dcxm:descriptionSet>

XML Example 5: The Description Element

In the remainder of this document, Description Elements are shown using an XML element with an expanded name with the XML Namespace Name http://dublincore.org/xml/dc-xml-min/2006/09/18/ and local name description (represented by the XML QName dcxm:description). However, a Description Element may have a different element name if such a name is useful or neceesary for the particular application.

A description set may contain multiple descriptions.

In DC-XML-Min, each description is represented by a separate Description Element. The order of the Description Elements within a Description Set Element is not significant.

The following example shows a description set consisting of two descriptions:

<?xml version="1.0"?>
<dcxm:descriptionSet
  xmlns:dcxm="http://dublincore.org/xml/dc-xml-min/2006/09/18/"
  xmlns:dc="http://purl.org/dc/elements/1.1/">
  <dcxm:description> <!-- 1st Description Element -->
    <dc:title>DCMI Home Page</dc:title>
  </dcxm:description>
  <dcxm:description> <!-- 2nd Description Element -->
    <dc:title>UKOLN Home Page</dc:title>
  </dcxm:description>
</dcxm:descriptionSet>

XML Example 6: Multiple Description Elements

The encoding of description sets with multiple descriptions is described further in section 3.6.

3.3.1 The Resource URI

A description may have an associated resource URI.

In DC-XML-Min, a resource URI is represented as the value of an XML attribute of the Description Element. The attribute has the name dcx:resourceURI.

The examples below show a description with the resource URI http://dublincore.org/pages/home.

<?xml version="1.0"?>
<dcxm:descriptionSet
  xmlns:dcxm="http://dublincore.org/xml/dc-xml-min/2006/09/18/"
  xmlns:dc="http://purl.org/dc/elements/1.1/">
  <dcxm:description
    dcxm:resourceURI="http://dublincore.org/pages/home"> <!-- resource URI -->
    <dc:title>DCMI Home Page</dc:title>
  </dcxm:description>
</dcxm:descriptionSet>

XML Example 7: The Resource URI Attribute

Note that the representation of the resource URI may be abbreviated through the use of an XML entity reference or a URI relative reference (see Section 3.1.1).

A Description Element contains one or more Statement Elements.

3.4 Encoding Statements: Statement Elements

A description is made up of one or more statements.

In DC-XML-Min, each child XML element of a Description Element represents a single statement and is known as a Statement Element.

The following example shows a description consisting of a single statement:

<?xml version="1.0"?>
<dcxm:descriptionSet
  xmlns:dcxm="http://dublincore.org/xml/dc-xml-min/2006/09/18/"
  xmlns:dc="http://purl.org/dc/elements/1.1/">
  <dcxm:description
        dcxm:resourceURI="http://dublincore.org/pages/home">
    <dc:title>DCMI Home Page</dc:title> <!-- Statement Element -->
  </dcxm:description>
</dcxm:descriptionSet>

XML Example 8: A Statement Element

A description may be made up of multiple statements.

In DC-XML-Min, each statement is represented by a separate Statement Element. The order of the Statement Elements within a Description Element is not significant.

The following example shows a description consisting of two statements:

<?xml version="1.0"?>
<dcxm:descriptionSet
  xmlns:dcxm="http://dublincore.org/xml/dc-xml-min/2006/09/18/"
  xmlns:dc="http://purl.org/dc/elements/1.1/">
  <dcxm:description
        dcxm:resourceURI="http://dublincore.org/pages/home">
    <dc:title>DCMI Home Page</dc:title>  <!-- Statement Element -->
    <dc:publisher>Dublin Core Metadata Initiative</dc:publisher>  <!-- Statement Element -->
  </dcxm:description>
</dcxm:descriptionSet>

XML Example 9: Multiple Statement Elements

3.4.1 The Property URI

A statement must contain exactly one property URI.

In DC-XML-Min, the property URI is represented by the element name of the Statement Element (an XML QName). The property URI is determined from the QName by applying the QName-URI mapping described in section 3.1.2.

The example belows show a description consisting of two statements where the property URIs are http://purl.org/dc/elements/1.1/title and http://purl.org/dc/elements/1.1/publisher.

<?xml version="1.0"?>
<dcxm:descriptionSet
  xmlns:dcxm="http://dublincore.org/xml/dc-xml-min/2006/09/18/"
  xmlns:dc="http://purl.org/dc/elements/1.1/">
  <dcxm:description
        dcxm:resourceURI="http://dublincore.org/pages/home">
                 <!-- property URI as QName of Statement Element -->
    <dc:title>DCMI Home Page</dc:title>
                 <!-- property URI as QName of Statement Element -->
    <dc:publisher>Dublin Core Metadata Initiative</dc:publisher>
  </dcxm:description>
</dcxm:descriptionSet>

XML Example 10: The Property URI

3.4.2 The Value URI

A statement may contain a value URI.

In DC-XML-Min, a value URI is represented as the value of an XML attribute of the Statement Element. The attribute has the name dcx:valueURI.

The example below shows a description consisting of two statements where the second statement includes the value URI http://example.org/agents/DCMI.

<?xml version="1.0"?>
<dcxm:descriptionSet
  xmlns:dcxm="http://dublincore.org/xml/dc-xml-min/2006/09/18/"
  xmlns:dc="http://purl.org/dc/elements/1.1/">
  <dcxm:description
        dcxm:resourceURI="http://dublincore.org/pages/home">
    <dc:title>DCMI Home Page</dc:title>
                <!-- value URI -->
    <dc:publisher 
          dcxm:valueURI="http://example.org/agents/DCMI">Dublin Core Metadata Initiative</dc:publisher>
  </dcxm:description>
</dcxm:descriptionSet>

XML Example 11: The Value URI Attribute

Note that the representation of the value URI may be abbreviated through the use of an XML entity reference or a URI relative reference (see Section 3.1.1).

3.4.3 The Vocabulary Encoding Scheme URI Attribute

A statement may include a vocabulary encoding scheme URI.

In DC-XML-Min, a vocabulary encoding scheme URI is represented as the value of an XML attribute of the Statement Element. The attribute has the name dcxm:vocabEncSchemeURI.

The example below shows a description consisting of three statements where the third statement includes the vocabulary encoding scheme URI http://purl.org/dc/terms/LCSH.

<?xml version="1.0"?>
<dcxm:descriptionSet
  xmlns:dcxm="http://dublincore.org/xml/dc-xml-min/2006/09/18/"
  xmlns:dc="http://purl.org/dc/elements/1.1/">
  <dcxm:description
        dcxm:resourceURI="http://dublincore.org/pages/home">
    <dc:title>DCMI Home Page</dc:title>
    <dc:publisher 
          dcxm:valueURI="http://example.org/agents/DCMI">Dublin Core Metadata Initiative</dc:publisher>
                <!-- vocabulary encoding scheme URI -->
    <dc:subject 
          dcxm:vocabEncSchemeURI="http://purl.org/dc/terms/LCSH">Metadata</dc:subject>
  </dcxm:description>
</dcxm:descriptionSet>

XML Example 12: The Vocabulary Encoding Scheme URI Attribute

Note that the representation of the vocabulary encoding scheme URI may be abbreviated through the use of an XML entity reference or a URI relative reference (see Section 3.1.1).

3.4.4 The Value Class URI Attribute

A statement may include a value class URI.

In DC-XML-Min, a value class URI is represented as the value of an XML attribute of the Statement Element. The attribute has the name dcxm:valueClassURI.

The example below shows a description consisting of three statements where the third statement includes the value class URI http://example.org/terms/Concept.

<?xml version="1.0"?>
<dcxm:descriptionSet
  xmlns:dcxm="http://dublincore.org/xml/dc-xml-min/2006/09/18/"
  xmlns:dc="http://purl.org/dc/elements/1.1/">
  <dcxm:description
        dcxm:resourceURI="http://dublincore.org/pages/home">
    <dc:title>DCMI Home Page</dc:title>
    <dc:publisher 
          dcxm:valueURI="http://example.org/agents/DCMI">Dublin Core Metadata Initiative</dc:publisher>
                <!-- value class URI -->
    <dc:subject 
          dcxm:valueClassURI="http://example.org/terms/Concept"
          dcxm:vocabEncSchemeURI="http://purl.org/dc/terms/LCSH">Metadata</dc:subject>
  </dcxm:description>
</dcxm:descriptionSet>

XML Example 13: The Value Class URI Attribute

Note that the representation of the value class URI may be abbreviated through the use of an XML entity reference or a URI relative reference (see Section 3.1.1).

3.4.5 Empty Statement Elements

The presence of a value representation in a statement is optional.

In DC-XML-Min, the Statement Element may therefore be empty.

The example below shows a description consisting of four statements where the fourth statement provides a value URI but no value representation.

<?xml version="1.0"?>
<dcxm:descriptionSet
  xmlns:dcxm="http://dublincore.org/xml/dc-xml-min/2006/09/18/"
  xmlns:dc="http://purl.org/dc/elements/1.1/"
  xmlns:dcterms="http://purl.org/dc/terms/">
  <dcxm:description
        dcxm:resourceURI="http://dublincore.org/pages/home">
    <dc:title>DCMI Home Page</dc:title>
    <dc:publisher 
          dcxm:valueURI="http://example.org/agents/DCMI">Dublin Core Metadata Initiative</dc:publisher>
                <!-- value class URI -->
    <dc:subject 
          dcxm:valueClassURI="http://example.org/terms/Concept"
          dcxm:vocabEncSchemeURI="http://purl.org/dc/terms/LCSH">Metadata</dc:subject>
    <!-- statement with no value representation -->
    <dcterms:isPartOf
          dcxm:valueURI="http://dublincore.org/site" />
  </dcxm:description>
</dcxm:descriptionSet>

XML Example 14: Empty Statement Element

3.5 Encoding Value Strings

In the subset of the DCAM dsecription model supported by DC-XML-Min, a statement may include a single value representation in the form of a value string.

In DC-XML-Min, the value string is represented by the content of the Statement Element.

The example below shows a description consisting of four statements where the first three statements each include a value string.

<?xml version="1.0"?>
<dcxm:descriptionSet
  xmlns:dcxm="http://dublincore.org/xml/dc-xml-min/2006/09/18/"
  xmlns:dc="http://purl.org/dc/elements/1.1/"
  xmlns:dcterms="http://purl.org/dc/terms/">
  <dcxm:description
        dcxm:resourceURI="http://dublincore.org/pages/home">
          <!-- value string as element content -->
    <dc:title>DCMI Home Page</dc:title>
          <!-- value string as element content -->
    <dc:publisher 
          dcxm:valueURI="http://example.org/agents/DCMI">Dublin Core Metadata Initiative</dc:publisher>
          <!-- value string as element content -->
    <dc:subject 
          dcxm:valueClassURI="http://example.org/terms/Concept"
          dcxm:vocabEncSchemeURI="http://purl.org/dc/terms/LCSH">Metadata</dc:subject>
    <dcterms:isPartOf
          dcxm:valueURI="http://dublincore.org/site" />
  </dcxm:description>
</dcxm:descriptionSet>

XML Example 15: The Value String

3.5.1.1 The Value String Language

A value string may have an associated value string language.

In DC-XML-Min, a value string language is represented by an xml:lang attribute of the Statement Element representing the value string.

The example below shows a description consisting of three statements where the first statement has an associated value string language "en-GB" with the value string "DCMI Home Page":

<?xml version="1.0"?>
<dcxm:descriptionSet
  xmlns:dcxm="http://dublincore.org/xml/dc-xml-min/2006/09/18/"
  xmlns:dc="http://purl.org/dc/elements/1.1/"
  xmlns:dcterms="http://purl.org/dc/terms/">
  <dcxm:description
        dcxm:resourceURI="http://dublincore.org/pages/home">
          <!-- value string language -->
    <dc:title
          xml:lang="en-GB">DCMI Home Page</dc:title>
    <dc:publisher 
          dcxm:valueURI="http://example.org/agents/DCMI">Dublin Core Metadata Initiative</dc:publisher>
    <dc:subject 
          dcxm:valueClassURI="http://example.org/terms/Concept"
          dcxm:vocabEncSchemeURI="http://purl.org/dc/terms/LCSH">Metadata</dc:subject>
    <dcterms:isPartOf
          dcxm:valueURI="http://dublincore.org/site" />
  </dcxm:description>
</dcxm:descriptionSet>

XML Example 16: The Value String Language

3.5.1.2 The Syntax Encoding Scheme URI

A value string may have an associated syntax encoding scheme URI.

In DC-XML-Min, a syntax encoding scheme URI is represented as the value of an XML attribute of the Statement Element. The attribute has the name dcxm:syntaxEncSchemeURI.

The examples below show a description consisting of three statements where the third statement associates the syntax encoding scheme URI http://www.w3.org/2001/XMLSchema#date with the value string "2005-05-05":

<?xml version="1.0"?>
<dcxm:descriptionSet
  xmlns:dcxm="http://dublincore.org/xml/dc-xml-min/2006/09/18/"
  xmlns:dc="http://purl.org/dc/elements/1.1/">
  <dcxm:description
        dcxm:resourceURI="http://dublincore.org/pages/home">
    <dc:title
          xml:lang="en-GB">DCMI Home Page</dc:title>
    <dc:publisher 
          dcxm:valueURI="http://example.org/agents/DCMI">Dublin Core Metadata Initiative</dc:publisher>
                       <!-- syntax encoding scheme URI -->
    <dc:date 
          dcxm:syntaxEncSchemeURI="http://www.w3.org/2001/XMLSchema#date">2005-05-05</dc:date>
  </dcxm:description>
</dcxm:descriptionSet>

XML Example 17: The Syntax Encoding Scheme URI Attribute

3.6 Encoding Descriptions of Values

As noted in section 3.3, description sets may contain multiple descriptions. Each description is represented by a separate Description Element. The order of the Description Elements has no significance.

It may be that the value of a statement in one description is the described resource of a second description within the description set. If that resource has been assigned a URI, then that URI appears as the value URI in the statement where the resource is the value and as a resource URI in the description of that resource, as shown below:

<?xml version="1.0"?>
<dcxm:descriptionSet
  xmlns:dcxm="http://dublincore.org/xml/dc-xml-min/2006/09/18/"
  xmlns:dc="http://purl.org/dc/elements/1.1/"
  xmlns:my="http://my.example.org/terms/">
  <dcxm:description
        dcxm:resourceURI="http://dublincore.org/pages/home">
    <dc:title>DCMI Home Page</dc:title>
    <dc:publisher 
          dcxm:valueURI="http://example.org/agents/DCMI"/>
  </dcxm:description>
  <dcxm:description
    dcxm:resourceURI="http://dublincore.org/pages/althome">
    <dc:title>DCMI Alternative Home Page</dc:title>
    <dc:publisher 
          dcxm:valueURI="http://example.org/agents/DCMI"/>
  </dcxm:description>
                     <!-- value URI used as resource URI in related description -->
  <dcxm:description
        dcxm:resourceURI="http://example.org/agents/DCMI">
    <my:name>Dublin Core Metadata Initiative</my:name>
  </dcxm:description>
</dcxm:descriptionSet>

XML Example 18: Value as Described Resource

In some cases the resource will not have a URI assigned, or the URI will not be known. Such a resource may still be a value in a statement and the described resource of another description in the same description set.

In such cases, the association between the statement and the second description is made by labelling the second description using an XML attribute of the Description Element. The attribute has the name dcxm:descriptionId. The attribute value may then be cited in the the value of a dcxm:descriptionRef XML attribute of one or more Statement Elements elsewhere in the same description set. Each value of a dcxm:descriptionRef XML attribute must match the value of a dcxm:descriptionId attribute in the same DC-XML-Min instance.

Note that this is a syntactic mechanism for linking references to values in statements to the descriptions of those values: the label itself does not appear in the description set.

<?xml version="1.0"?>
<dcxm:descriptionSet
  xmlns:my="http://my.example.org/terms/"
  xmlns:dcxm="http://dublincore.org/xml/dc-xml-min/2006/09/18/"
  xmlns:dc="http://purl.org/dc/elements/1.1/">
  <dcxm:description
        dcxm:resourceURI="http://dublincore.org/pages/home">
    <dc:title>DCMI Home Page</dc:title>
    <!-- Reference to related description using label -->
    <dc:publisher 
          dcxm:descriptionRef="DCMI"/>
  </dcxm:description>
  <dcxm:description
        dcxm:resourceURI="http://dublincore.org/pages/home">
    <dc:title>DCMI Alternative Home Page</dc:title>
    <!-- Reference to related description using label -->
    <dc:publisher 
          dcxm:descriptionRef="DCMI"/>
  </dcxm:description>
  <!-- Related description with label -->
  <dcxm:description dcxm:descriptionId="DCMI">
    <my:name>Dublin Core Metadata Initiative</my:name>
  </dcxm:description>
</dcxm:descriptionSet>

XML Example 19: Value as Described Resource

4. GRDDL

An XSLT transformation from DC-XML-Min to RDF/XML [RDFXML] is available.

The GRDDL specification [GRDDL] defines a set of conventions for associating an XML instance document with a transformation.

One approach is to reference the transformation using an attribute of the root element, as follows:

<?xml version="1.0"?>
<dcxm:descriptionSet
  xmlns:dcxm="http://dublincore.org/xml/dc-xml-min/2006/09/18/"
  xmlns:data-view="http://www.w3.org/2003/g/data-view#"
  data-view:transformation="dcxm2rdfxml.xsl">
  ...
</dcxm:descriptionSet>

XML Example 35: GRDDL

The transformation can also be associated with a set of XML documents through information provided by the "namespace document".

Appendix A. DC-TEXT Representation of Examples

This appendix provides representations of all the examples provided in the main body of the document using the DC-Text syntax [DC-TEXT].

A.1 Example 1

The DC-XML-Min instance in Example 1 represents the following description set:

@prefix dc: <http://purl.org/dc/elements/1.1/> .
DescriptionSet (
  Description (
    ResourceURI ( <http://dublincore.org/pages/home> )
    Statement (
      PropertyURI ( dc:title )
      ValueString ( "DCMI Home Page" )
    )
  )
)

A.2 Example 2

The DC-XML-Min instance in Example 2 represents the following description set:

@prefix dc: <http://purl.org/dc/elements/1.1/> .
DescriptionSet (
  Description (
    ResourceURI ( <http://dublincore.org/pages/home> )
    Statement (
      PropertyURI ( dc:title )
      ValueString ( "DCMI Home Page" )
    )
  )
)

A.3 Example 3

The DC-XML-Min instance in Example 3 represents the following description set:

@prefix dc: <http://purl.org/dc/elements/1.1/> .
DescriptionSet (
  Description (
    ResourceURI ( <http://dublincore.org/pages/home> )
    Statement (
      PropertyURI ( dc:title )
      ValueString ( "DCMI Home Page" )
    )
  )
)

A.4 Example 4

The DC-XML-Min instance in Example 4 represents the following description set:

@prefix dc: <http://purl.org/dc/elements/1.1/> .
DescriptionSet (
  Description (
    Statement (
      PropertyURI ( dc:title )
      ValueString ( "DCMI Home Page" )
    )
  )
)

A.5 Example 5

The DC-XML-Min instance in Example 5 represents the following description set:

@prefix dc: <http://purl.org/dc/elements/1.1/> .
DescriptionSet (
  Description (
    Statement (
      PropertyURI ( dc:title )
      ValueString ( "DCMI Home Page" )
    )
  )
)

A.6 Example 6

The DC-XML-Min instance in Example 6 represents the following description set:

@prefix dc: <http://purl.org/dc/elements/1.1/> . 
DescriptionSet (
  Description (
    Statement (
      PropertyURI ( dc:title )
      ValueString ( "DCMI Home Page" )
    )
  )
  Description (
    Statement (
      PropertyURI ( dc:title )
      ValueString ( "UKOLN Home Page" )
    )
  )
)

A.7 Example 7

The DC-XML-Min instance in Example 7 represents the following description set:

@prefix dc: <http://purl.org/dc/elements/1.1/> .
DescriptionSet (
  Description (
    ResourceURI ( <http://dublincore.org/pages/home> )
    Statement (
      PropertyURI ( dc:title )
      ValueString ( "DCMI Home Page" )
    )
  )
)

A.8 Example 8

The DC-XML-Min instance in Example 8 represents the following description set:

@prefix dc: <http://purl.org/dc/elements/1.1/> .
DescriptionSet (
  Description (
    ResourceURI ( <http://dublincore.org/pages/home> )
    Statement (
      PropertyURI ( dc:title )
      ValueString ( "DCMI Home Page" )
    )
  )
)

A.9 Example 9

The DC-XML-Min instance in Example 9 represents the following description set:

@prefix dc: <http://purl.org/dc/elements/1.1/> .
DescriptionSet (
  Description (
    ResourceURI ( <http://dublincore.org/pages/home> )
    Statement (
      PropertyURI ( dc:title )
      ValueString ( "DCMI Home Page" )
    )
    Statement (
      PropertyURI ( dc:publisher )
      ValueString ( "Dublin Core Metadata Initiative" )
    )
  )
)

A.10 Example 10

The DC-XML-Min instance in Example 10 represents the following description set:

@prefix dc: <http://purl.org/dc/elements/1.1/> .
DescriptionSet (
  Description (
    ResourceURI ( <http://dublincore.org/pages/home> )
    Statement (
      PropertyURI ( dc:title )
      ValueString ( "DCMI Home Page" )
    )
    Statement (
      PropertyURI ( dc:publisher )
      ValueString ( "Dublin Core Metadata Initiative" )
    )
  )
)

A.11 Example 11

The DC-XML-Min instance in Example 11 represents the following description set:

@prefix dc: <http://purl.org/dc/elements/1.1/> .
DescriptionSet (
  Description (
    ResourceURI ( <http://dublincore.org/pages/home> )
    Statement (
      PropertyURI ( dc:title )
      ValueString ( "DCMI Home Page" )
    )
    Statement (
      PropertyURI ( dc:publisher )
      ValueURI ( <http://example.org/agents/DCMI> )
      ValueString ( "Dublin Core Metadata Initiative" )
    )
  )
)

A.12 Example 12

The DC-XML-Min instance in Example 12 represents the following description set:

@prefix dc: <http://purl.org/dc/elements/1.1/> .
DescriptionSet (
  Description (
    ResourceURI ( <http://dublincore.org/pages/home> )
    Statement (
      PropertyURI ( dc:title )
      ValueString ( "DCMI Home Page" )
    )
    Statement (
      PropertyURI ( dc:publisher )
      ValueURI ( <http://example.org/agents/DCMI> )
      ValueString ( "Dublin Core Metadata Initiative" )
    )
    Statement (
      PropertyURI ( dc:subject )
      VocabularyEncodingSchemeURI ( <http://purl.org/dc/terms/LCSH> )
      ValueString ( "Metadata" )
    )
  )
)

A.13 Example 13

The DC-XML-Min instance in Example 13 represents the following description set:

@prefix dc: <http://purl.org/dc/elements/1.1/> .
DescriptionSet (
  Description (
    ResourceURI ( <http://dublincore.org/pages/home> )
    Statement (
      PropertyURI ( dc:title )
      ValueString ( "DCMI Home Page" )
    )
    Statement (
      PropertyURI ( dc:publisher )
      ValueURI ( <http://example.org/agents/DCMI> )
      ValueString ( "Dublin Core Metadata Initiative" )
    )
    Statement (
      PropertyURI ( dc:subject )
      ValueClassURI ( <http://example.org/terms/Concept> )
      VocabularyEncodingSchemeURI ( <http://purl.org/dc/terms/LCSH> )
      ValueString ( "Metadata" )
    )
  )
)

A.14 Example 14

The DC-XML-Min instance in Example 14 represents the following description set:

@prefix dc: <http://purl.org/dc/elements/1.1/> .
DescriptionSet (
  Description (
    ResourceURI ( <http://dublincore.org/pages/home> )
    Statement (
      PropertyURI ( dc:title )
      ValueString ( "DCMI Home Page" )
    )
    Statement (
      PropertyURI ( dc:publisher )
      ValueURI ( <http://example.org/agents/DCMI> )
      ValueString ( "Dublin Core Metadata Initiative" )
    )
    Statement (
      PropertyURI ( dc:subject )
      ValueClassURI ( <http://example.org/terms/Concept> )
      VocabularyEncodingSchemeURI ( <http://purl.org/dc/terms/LCSH> )
      ValueString ( "Metadata" )
    )
    Statement (
      PropertyURI ( dcterms:isPartOf )
      ValueURI ( <http://dublincore.org/site> )
    )
  )
)

A.15 Example 15

The DC-XML-Min instance in Example 15 represents the following description set:

@prefix dc: <http://purl.org/dc/elements/1.1/> .
@prefix dcterms: <http://purl.org/dc/terms/> .
DescriptionSet (
  Description (
    ResourceURI ( <http://dublincore.org/pages/home> )
    Statement (
      PropertyURI ( dc:title )
      ValueString ( "DCMI Home Page" )
    )
    Statement (
      PropertyURI ( dc:publisher )
      ValueURI ( <http://example.org/agents/DCMI> )
      ValueString ( "Dublin Core Metadata Initiative" )
    )
    Statement (
      PropertyURI ( dc:subject )
      ValueClassURI ( <http://example.org/terms/Concept> )
      VocabularyEncodingSchemeURI ( <http://purl.org/dc/terms/LCSH> )
      ValueString ( "Metadata" )
    )
    Statement (
      PropertyURI ( dcterms:isPartOf )
      ValueURI ( <http://dublincore.org/site> )
    )
  )
)

A.16 Example 16

The DC-XML-Min instance in Example 16 represents the following description set:

@prefix dc: <http://purl.org/dc/elements/1.1/> .
DescriptionSet (
  Description (
    ResourceURI ( <http://dublincore.org/pages/home> )
    Statement (
      PropertyURI ( dc:title )
      ValueString ( "DCMI Home Page" 
        Language ( en-GB )
      )
    )
    Statement (
      PropertyURI ( dc:publisher )
      ValueURI ( <http://example.org/agents/DCMI> )
      ValueString ( "Dublin Core Metadata Initiative" )
    )
    Statement (
      PropertyURI ( dc:date )
      ValueString ( "2005-05-05" )
    )
  )
)

A.17 Example 17

The DC-XML-Min instance in Example 17 represents the following description set:

@prefix dc: <http://purl.org/dc/elements/1.1/> .
DescriptionSet (
  Description (
    ResourceURI ( <http://dublincore.org/pages/home> )
    Statement (
      PropertyURI ( dc:title )
      ValueString ( "DCMI Home Page" 
        Language ( en-GB )
      )
    )
    Statement (
      PropertyURI ( dc:publisher )
      ValueURI ( <http://example.org/agents/DCMI> )
      ValueString ( "Dublin Core Metadata Initiative" )
    )
    Statement (
      PropertyURI ( dc:date )
      ValueString ( "2005-05-05"
        SyntaxEncodingSchemeURI ( <http://www.w3.org/2001/XMLSchema#date> )
      )
    )
  )
)

A.18 Example 18

The DC-XML-Min instance in Example 18 represents the following description set:

@prefix dc: <http://purl.org/dc/elements/1.1/> .
@prefix my: <http://my.example.org/terms/> .
DescriptionSet (
  Description (
    ResourceURI ( <http://dublincore.org/pages/home> )
    Statement (
      PropertyURI ( dc:title )
      ValueString ( "DCMI Home Page" )
    )
    Statement (
      PropertyURI ( dc:publisher )
      ValueURI ( <http://example.org/agents/DCMI> )
    )
  )
  Description (
    ResourceURI ( <http://dublincore.org/pages/althome> )
    Statement (
      PropertyURI ( dc:title )
      ValueString ( "DCMI Alternative Home Page" )
    )
    Statement (
      PropertyURI ( dc:publisher )
      ValueURI ( <http://example.org/agents/DCMI> )
    )
  )
  Description (
    ResourceURI ( <http://example.org/agents/DCMI> )
    Statement (
      PropertyURI ( my:name )
      ValueString ( "Dublin Core Metadata Initiative" )
    )
  )
)

A.19 Example 19

The DC-XML-Min instance in Example 19 represents the following description set:

@prefix dc: <http://purl.org/dc/elements/1.1/> .
@prefix my: <http://my.example.org/terms/> .
DescriptionSet (
  Description (
    ResourceURI ( <http://dublincore.org/pages/home> )
    Statement (
      PropertyURI ( dc:title )
      ValueString ( "DCMI Home Page" )
    )
    Statement (
      PropertyURI ( dc:publisher )
      DescriptionRef ( descDCMI )
    )
  )
  Description (
    ResourceURI ( <http://dublincore.org/pages/althome> )
    Statement (
      PropertyURI ( dc:title )
      ValueString ( "DCMI Alternative Home Page" )
    )
    Statement (
      PropertyURI ( dc:publisher )
      DescriptionRef ( descDCMI )
    )
  )
  Description (
    DescriptionId ( descDCMI )
    Statement (
      PropertyURI ( my:name )
      ValueString ( "Dublin Core Metadata Initiative" )
    )
  )
)

Notes

[1] This document defines one XML format for representing DC metadata description sets in XML. Other formats may exist supporting other subsets of the DCMI Abstract Model. For example, the Open Archives Initiative Protocol for Metadata Harvesting [OAIPMH] defines a format, commonly known as oai_dc, which supports the serialisation only of description sets containing a single description, with statements referencing only the fifteen properties of the DCMES, and using value strings only. oai_dc is a different XML format from DC-XML-Min, but that does not change the value and usefulness of oai_dc as a format for serialising that particular subset of DC metadata description sets.

[2] In this document the term "element" is used to refer only to XML elements, and it should always be interpreted in that sense wherever it occurs. It is not used to refer to the properties of the DCMES.

References

[DCAM]
DCMI Abstract Model
http://dublincore.org/documents/abstract-model/

[XML]
Extensible Markup Language (XML) 1.0 (Third Edition). W3C Recommendation 04 February 2004.
http://www.w3.org/TR/REC-xml

[XMLSCHEMA]
XML Schema Part 0: Primer Second Edition. W3C Recommendation 28 October 2004.
http://www.w3.org/TR/xmlschema-0/

[RFC3986]
Uniform Resource Identifier (URI): Generic Syntax.
http://www.ietf.org/rfc/rfc3986.txt

[XMLNS]
Namespaces in XML (Second Edition). W3C Recommendation 16 August 2006.
http://www.w3.org/TR/REC-xml-names

[RDFXML]
RDF/XML Syntax Specification (Revised) W3C Recommendation 10 February 2004.
http://www.w3.org/TR/rdf-syntax-grammar/

[GRDDL]
Gleaning Resource Descriptions from Dialects of Languages (GRDDL) W3C Team Submission 16 May 2005
http://www.w3.org/TeamSubmission/grddl/

[OAIPMH]
The Open Archives Initiative Protocol for Metadata Harvesting Protocol Version 2.0 of 2002-06-14.
http://www.openarchives.org/OAI/openarchivesprotocol.html

[DC-TEXT]
DC-Text: A Text Syntax for Dublin Core Metadata Draft of 2006-09-18.
http://dublincore.org/architecturewiki/DCText/2006-09-18

Changes in this version

• Initial version