cmr.xsd

<?xml version="1.0" encoding="UTF-8"?>

<xsd:schema
  xmlns="http://canadiana.ca/schema/2012/xsd/cmr"
  xmlns:xsd="http://www.w3.org/2001/XMLSchema"
  targetNamespace="http://canadiana.ca/schema/2012/xsd/cmr" 
  elementFormDefault="qualified" attributeFormDefault="unqualified" version="1.0"
>

  <xsd:annotation>
    <xsd:documentation>
      <h1>CMR version 1.2 WORKING DRAFT (November 2012)</h1>

      <h2>Status</h2>

      <p>This is a working draft of CMR version 1.2. It is
      backwards-compatible with CMR 1.1 and 1.0, provided that the
      appropriate namespace declarations are used.</p>

      <h2>Changes from version 1.1</h2>

      <p>Version 1.2 adds documentation and a target namespace to the
      schema and allows image/jp2 as a MIME type. Version 1.1 and earlier
      records should validate against the 1.2 schema provided that they
      add the namespace declaration:
      xmlns="http://canadiana.ca/schema/2012/xsd/cmr" to the root
      &lt;recordset&gt; element. There are no other structural changes to
      the CMR format itself.</p>

      <h2>Abstract</h2>

      <p>CMR is the metadata format used within the Canadiana Metadata
      Repository as a normalized storage format. Metadata records
      contributed to the Repository have CMR records derived from them,
      which are then used to build the national index on which the
      Canadiana Discovery Portal (http://search.canadiana.ca) is
      based.</p>

      <p>Contributors may elect to submit metadata to the repository
      directly in CMR format. Those who do should follow the standards and
      practices described in this document to ensure that their records
      validate against the schema and function optimally within the
      Discovery Portal.</p>

      <h2>Important Notes About Usage</h2>

      <p>CMR was originally intended for internal use for the purpose of
      normalizing metadata from a variety of sources and in a variety of
      formats so that they could be indexed into a single index for
      inclusion in the Canadiana Discovery Portal. As a result, the
      definition and application of various fields, particularly with
      regards to descriptive metadata, is quite loose and subject to
      change over time. The specificity of element names (e.g.,
      &lt;author&gt; is, in many cases, accidental and, in general, are
      meant to be interpreted liberally. The specific indexing and display
      behaviour of the Discovery Portal may change over time;
      documentation about the use of descriptive metadata (child elements
      of the &lt;description&gt; element) should be viewed as provisional
      guidelines.</p>

    </xsd:documentation>
  </xsd:annotation>

  <xsd:element name="recordset">
    <xsd:annotation>
      <xsd:documentation>
        <p>A &lt;recordset&gt; is the top-level element in a CMR record. It
        contains zero or more &lt;record&gt; elements. The individual
        records in a recordset do not have to be related in any particular
        way, but all page records should be included in the same recordset
        as their parent document record in order to be properly indexed
        and linked. Orphaned page records cannot be properly indexed and
        will have limited findability and accessibility.</p>

        <p>The &lt;recordset&gt; element must include the version
        attribute which indicates the version of CMR that is being used.
        The correct value for this version is "1.2".</p>
      </xsd:documentation>
    </xsd:annotation>
    <xsd:complexType>
      <xsd:sequence>

        <!-- Record -->
        <xsd:element name="record" minOccurs="0" maxOccurs="unbounded">
          <xsd:annotation>
            <xsd:documentation>
              <p>A record describes an addressable digital resource. It
              can refer to a complete item (such as a book) or an sub-part
              of an item (such as a page), so long as the item can be
              accessed at the level described. For example, if a book is
              only available as a single PDF document, only one record
              should be created for the book as a whole. If, on the other
              hand, each page of the book is also directly viewable (for
              example as a JPEG image) and has a distinct URL for viewing,
              then one record may be created for the book with a
              &lt;type&gt; element of "document" and a linked child record
              for each page with the &lt;type&gt; page.</p>
              <p>The creation of multi-record hierarchical objects (e.g.
              books + pages) is not required if it is desired to only
              provide searchable access at the level of the item as a
              whole.</p>
              <p>Refer to the &lt;type&gt; element for more details on
              hierarchical objects.</p>
            </xsd:documentation>
          </xsd:annotation>
          <xsd:complexType>
            <xsd:sequence>

              <!-- Required control fields -->
              <xsd:element name="type">
                <xsd:annotation>
                  <xsd:documentation>
                    <p>The &lt;type&gt; element is required for every
                    record. Its value should be one of: "series", "document"
                    or "page". Other values are deprecated and will be
                    mapped as follows: "collection" and "serial" are
                    treated the same as "series"; "issue" and "monograph"
                    are treated the same as "document".</p>
                    <p>"Document" is the base record type. A document can
                    represent a book, pamphlet, photograph, video or audio
                    recording, or just about any other kind of digital
                    object.</p>
                    <p>"Page" is used for records that describe an
                    individually-addressible part of a document. These may
                    be literal pages (as in the pages of a book) but they
                    can also be any other sort of sub-part. For example,
                    each individual track of a record album may be encoded
                    as a page record.</p>
                    <p>"Series" is used to denote a related set of
                    sequentially-ordered documents, such as a serial or
                    periodical.</p>
                    <p>The &lt;type&gt; element is used to determine the
                    functional behaviour of a record within the CMR.
                    Specifically, general searches will locate only
                    records of type "series" or "document". Page records
                    are found only by specifically searching pages,
                    usually in the context of a parent document record.
                    This element is not used to provide descriptive
                    information about the nature or format of the object:
                    this is done in the &lt;description&gt; section.</p>
                    <p>See the &lt;pkey&gt; documentation for details
                    about linking records into a herarchical
                    structure.</p>
                  </xsd:documentation>
                </xsd:annotation>
                <xsd:simpleType>
                  <xsd:restriction base="xsd:string">
                    <xsd:enumeration value="series"/>
                    <xsd:enumeration value="document"/>
                    <xsd:enumeration value="page"/>
                    <!-- The following values are deprecated: -->
                    <xsd:enumeration value="collection"/>
                    <xsd:enumeration value="issue"/>
                    <xsd:enumeration value="serial"/>
                    <xsd:enumeration value="monograph"/>
                  </xsd:restriction>
                </xsd:simpleType>
              </xsd:element>

              <xsd:element name="contributor" type="lcalpha">
                <xsd:annotation>
                  <xsd:documentation>
                    <p>Each record must have a contributor code. These
                    codes are assigned by Canadiana.org and are used to
                    identify the provenance of a record and, along with
                    the &lt;key&gt; element, to generate a unique
                    identifier for the record.</p>
                    <p>This field is mandatory and contributors should
                    populate it with their assigned code. Records
                    submitted with a &lt;contributor&gt; value of anything
                    other than the contributor's assigned code will be
                    replaced with the correct code.</p>
                  </xsd:documentation>
                </xsd:annotation>
              </xsd:element>

              <xsd:element name="key" type="key">
                <xsd:annotation>
                  <xsd:documentation>
                    <p>The &lt;key&gt; element is mandatory field used to
                    denote a unique identifier for this record. The
                    content of this field must be a string of no more than
                    127 characters and consisting only of ASCII
                    alphanumeric characters, underscores, dots and hyphens
                    (A-Za-z0-9_.-).</p>
                    <p>The key must be locally-unique to the contributor.
                    If two records from the same contributor with the same
                    key are encountered, the second will replace the
                    first.</p>
                    <p>A globally-unique CMR key is generated by
                    concatenating the &lt;contributor&gt; and &lt;key&gt;
                    fields together with a dot. This CMR key can be used
                    to uniquely identify any object within the
                    repository.</p>
                    <p>It is recommended that page records be assigned a
                    key that is an extension of the parent document's key
                    (for example, by appending ".1", ".2", etc. to the
                    parent key) but this is not a requirement.</p>
                  </xsd:documentation>
                </xsd:annotation>
              </xsd:element>

              <xsd:element name="label" type="text">
                <xsd:annotation>
                  <xsd:documentation>
                    <p>This &lt;label&gt; is a required element and is
                    used to store the standard label for the object. For
                    documents and series, this is most often a title, but
                    may be an abstract, identification number, or anything
                    else that serves as a standard descriptive reference
                    to the item.  For pages, it may be a page number or
                    description (e.g. "5", "p. 5" or "Table of Contents").
                    The label will appear as the main heading in search
                    resutls, bibliographic record displays, and so
                    forth.</p>
                    <p>For pages and documents that are part of a series,
                    the label should be relative to the context of the
                    containing record. For example, the label for an issue
                    of a series might consist of the volume and issue
                    number, with the common name ommitted. When displayed
                    out of context, the labels of the parent items will be
                    prepended to the label of the object. (E.g. a page
                    labeled "p. 5" from an issue labeled "vol. 1 no. 4"
                    from a series labeled "Canadian Builder" may be
                    displayed as "Canadian Builder: vol. 1 no. 4, p.
                    5".)</p>
                  </xsd:documentation>
                </xsd:annotation>
              </xsd:element>

              <!-- Optional control fields -->
              <xsd:element name="pkey" type="key" minOccurs="0">
                <xsd:annotation>
                  <xsd:documentation>
                    <p>The &lt;pkey&gt; field is used to link objects to
                    their parent objects. A page record should have a &lt;pkey&gt;
                    value equal to the &lt;key&gt; of the document it
                    belongs to. A document which is part of a series
                    should have a &lt;pkey&gt; equal to the &lt;key&gt; of
                    the series to which it belongs. Series and documents
                    which do not belong to a series should not have a
                    &lt;pkey&gt; element.</p>
                    <p>A &lt;pkey&gt; should only be specified if the
                    parent record it references is also included. Dangling
                    references may be ignored or may introduce invalid
                    links.</p>
                    <p>&lt;pkey&gt; values which reference documents of
                    the incorrect type must be ignored. I.e., the pkey of
                    a page must refer to a document, the pkey of a
                    document must refer to a series, and series must not
                    have pkeys.</p>
                  </xsd:documentation>
                </xsd:annotation>
              </xsd:element>

              <xsd:element name="gkey" type="key" minOccurs="0" maxOccurs="unbounded">
                <xsd:annotation>
                  <xsd:documentation>
                    <p>This element is deprecated and will be ignored.</p>
                  </xsd:documentation>
                </xsd:annotation>
              </xsd:element>

              <xsd:element name="seq" type="xsd:positiveInteger" minOccurs="0">
                <xsd:annotation>
                  <xsd:documentation>
                    <p>Any page or document record which has a parent
                    element (see &lt;pkey&gt;) should include a
                    &lt;seq&gt; element. The &lt;seq&gt; element's value
                    is a positive integer which specifies the position of
                    the page or document within its parent document or
                    series. The value is used to sort pages or issues into
                    the correct order.</p>
                    <p>It is recommended that the value of this element be
                    the ordinal position of the object within its parent
                    (e.g., the 5th page in a document object should have
                    &lt;sedq&gt;5&lt;seq&gt;) but any value is acceptable
                    as long as it places the object in correct numerical
                    order. It is acceptable to leave gaps in the sequence
                    for missing pages or issues.</p>
                    <p>No two records should have identical &lt;pkey&gt;
                    and &lt;seq&gt; values. If multiple records belonging
                    to the same parent also have the same sequence value,
                    they will in some cases sort in an indeterminate order
                    and in others one will mask the existence of the
                    others.</p>
                  </xsd:documentation>
                </xsd:annotation>
              </xsd:element>

              <xsd:element name="group" type="group" minOccurs="0" maxOccurs="unbounded">
                <xsd:annotation>
                  <xsd:documentation>
                    <p>This element is for internal use by Canadiana.org
                    and may be deprecated in future. If supplied, it will
                    be ignored.</p>
                  </xsd:documentation>
                </xsd:annotation>
              </xsd:element>

              <xsd:element name="pubdate" minOccurs="0">
                <xsd:annotation>
                  <xsd:documentation>
                    <p>This optional element specifies the date of
                    publication. It consists of two attributes: min and
                    max, each of which takes a date in ISO 8601 format.
                    The date must be fully specified in UTC, except that
                    fractional secords are optional. Example:
                    2012-12-31T13:00:00.000Z/</p>
                    <p>The &lt;pubdate&gt; element is used to limit
                    searches by date range and to sort records by
                    date.</p>
                    <p>The min and max attributes define a range of
                    possible publication dates for the item. For a
                    document, this should be the estimated date of
                    publication and for series it should be the estimated
                    run from first to last issue. Example: a book with a
                    publication date of 1905 should have &lt;pubdate
                    min="1905-01-01T00:00:00.000Z"
                    max="1905-12-31T23:59:259.999Z"/&gt;.</p>
                    <p>Page records should not include this element unless
                    it is different from the parent document's.</p>
                  </xsd:documentation>
                </xsd:annotation>
                <xsd:complexType>
                  <xsd:attribute name="min" type="iso8601" use="required"/>
                  <xsd:attribute name="max" type="iso8601" use="required"/>
                </xsd:complexType>
              </xsd:element>

              <xsd:element name="lang" type="iso639-3" minOccurs="0" maxOccurs="unbounded">
                <xsd:annotation>
                  <xsd:documentation>
                    <p>This element is optional. Its value should be a
                    3-character ISO 639-3 language code describing the
                    language of the content of the object. This field may
                    be repeated as required.</p>
                    <p>It is important to note that some ISO 639-2 codes
                    are not valid ISO 639-3 codes. In particular, keep in
                    mind that "fra", "deu" and "zho" should be used and
                    not "fre", "ger" and "chi".</p>
                    <p>Page records should omit this element unless they
                    are different from the parent document's.</p>
                  </xsd:documentation>
                </xsd:annotation>
              </xsd:element>

              <xsd:element name="media" minOccurs="0" maxOccurs="unbounded">
                <xsd:annotation>
                  <xsd:documentation>
                    <p>This element is used to indicate the format(s) in
                    which the digital object is available. It refers to
                    the normal mode of access of the digital object
                    itself, irrespective of the format of any original on
                    which the object might be based. The &lt;media&gt;
                    element is both descriptive and used to facet
                    searches. It may be repeated as required. Page records
                    should omit this element unless they are different
                    from the media type of the parent document.</p>
                    <p>Permissible values are any of the following:</p>
                    <ul>
                      <li>audio: a sound recording (e.g. an MP3 file)</li>
                      <li>data: machine-readable structured data (e.g. a
                      CSV file)</li>
                      <li>image: an image (e.g. JPEG file) of something
                      that is not primarily textual (photograph of an
                      artifact, poster, painting, etc.)</li>
                      <li>interactive: an interactive application
                      (interactive Web site, computer program, etc.)</li>
                      <li>plaintext: an unformatted machine-readable text
                      file (in most cases, text should also be specified
                      as a media type)</li>
                      <li>text: formatted or unformatted text or a
                      representation of text or primarily textual object
                      (PDF of a digitized book, scanned
                      page images encoded as JPEGs, etc.)</li>
                      <li>video: any moving picture or video format (e.g.
                      MPEG4)</li>
                    </ul>
                  </xsd:documentation>
                </xsd:annotation>
                <xsd:simpleType>
                  <xsd:restriction base="xsd:string">
                    <xsd:enumeration value="audio"/>
                    <xsd:enumeration value="data"/>
                    <xsd:enumeration value="image"/>
                    <xsd:enumeration value="interactive"/>
                    <xsd:enumeration value="plaintext"/>
                    <xsd:enumeration value="text"/>
                    <xsd:enumeration value="video"/>
                  </xsd:restriction>
                </xsd:simpleType>
              </xsd:element>

              <!-- Description and content: fields may appear in any quantity and order -->
              <xsd:element name="description">
                <xsd:annotation>
                  <xsd:documentation>
                    <p>The contents of this element are all free-form
                    descriptive metadata for the object. All child
                    elements are optional, repeatable and can be included
                    in any order. The contents of these fields are indexed
                    for keyword searching and are also used to construct
                    the majority of the bibliographic record for the
                    object.</p>
                    <p>Metadata for page records should reflect content
                    specific to that page. Usually, this is just the page
                    text or OCR. It is permissible to do page-level
                    subject assignments, notes, titles, etc., but note the
                    following caution:</p>
                    <p>Descriptive metadata in page records will be
                    exported into the parent record at index time. This
                    means that the content of a page's &lt;description&gt;
                    section will match the containing document for keyword
                    searches. It also means that metadata in the page
                    records will appear as part of the bibliographic
                    record for the parent document. Under normal
                    circumstances, page records should contain only
                    &lt;text&gt; elements in their &lt;description&gt;</p>
                  </xsd:documentation>
                </xsd:annotation>
                <xsd:complexType>
                  <xsd:group ref="descriptionFields" minOccurs="0" maxOccurs="unbounded"/>
                </xsd:complexType>
              </xsd:element>

              <!-- Resource links: some of these are required -->
              <xsd:element name="resource">
                <xsd:annotation>
                  <xsd:documentation>
                    <p>The &lt;resource&gt; element contains one or more
                    child elements with local or public pointers to
                    digital assets and other resources associated with the
                    object.</p>
                  </xsd:documentation>
                </xsd:annotation>
                <xsd:complexType>
                  <xsd:sequence>
                    <xsd:element name="canonicalUri" type="xsd:anyURI">
                      <xsd:annotation>
                        <xsd:documentation>
                          <p>This element is required and may only occur
                          once. Its value should be the canonical or
                          principal URI associated with the resource. This
                          may be a direct link to a representation of the
                          digital object itself (e.g. a PDF file) but is
                          more often a reference to a Web page containing
                          information about the object, an embedded
                          representation of the object and/or links to
                          access one or more digital representations of
                          the object.</p>
                        </xsd:documentation>
                      </xsd:annotation>
                    </xsd:element>
                    <xsd:element name="canonicalPreviewUri" type="xsd:anyURI" minOccurs="0">
                      <xsd:annotation>
                        <xsd:documentation>
                          <p>This element is optional. It should be a URI
                          pointing to a thumbnail image or similar
                          representation of the digital object in a format
                          that can normally be used as the value of the
                          src attribute of the HTML &lt;img&gt; element
                          (normally a JPEG or PNG image).</p>
                        </xsd:documentation>
                      </xsd:annotation>
                    </xsd:element>
                    <xsd:element name="canonicalMaster" type="resource" minOccurs="0">
                      <xsd:annotation>
                        <xsd:documentation>
                          <p>This element is used internally by
                          Canadiana.org and will be ignored in contributed
                          records.</p>
                        </xsd:documentation>
                      </xsd:annotation>
                    </xsd:element>
                    <xsd:element name="canonicalDownload" type="resource" minOccurs="0">
                      <xsd:annotation>
                        <xsd:documentation>
                          <p>This element is used internally by
                          Canadiana.org and will be ignored in contributed
                          records.</p>
                        </xsd:documentation>
                      </xsd:annotation>
                    </xsd:element>
                  </xsd:sequence>
                </xsd:complexType>
              </xsd:element>

            </xsd:sequence>
          </xsd:complexType>
        </xsd:element>
      </xsd:sequence>
      <xsd:attribute name="version" type="version" use="required"/>
    </xsd:complexType>
  </xsd:element>

  <!-- Description fields -->
  <xsd:group name="descriptionFields">
    <xsd:choice>
        <xsd:element name="title" minOccurs="0" maxOccurs="unbounded">
          <xsd:annotation>
            <xsd:documentation>
              <p>Use this element to indicate the title of the object. The
              lang and type attributes may be used to specify additional
              information about the title. Allowed values for type are
              "main" and "uniform". These values are intended to
              correspond roughly to MARC fields 245$a and 130 (or 730)
              respectively.</p>
            </xsd:documentation>
          </xsd:annotation>
          <xsd:complexType>
            <xsd:simpleContent>
              <xsd:extension base="text">
                <xsd:attribute name="lang" type="iso639-3" use="optional"/>
                <xsd:attribute name="type" use="optional">
                  <xsd:simpleType>
                    <xsd:restriction base="xsd:string">
                      <xsd:enumeration value="main"/>
                      <xsd:enumeration value="uniform"/>
                    </xsd:restriction>
                  </xsd:simpleType>
                </xsd:attribute>
              </xsd:extension>
            </xsd:simpleContent>
          </xsd:complexType>
        </xsd:element>

        <xsd:element name="author" minOccurs="0" maxOccurs="unbounded">
          <xsd:annotation>
            <xsd:documentation>
              <p>Use this element to denote the author or any sort of
              creator or similar contributor to the work. This element
              should be interpreted broadly, similar to the Dublin Core
              creator element. The optional type attribute may be assigned
              the value of "editor" to indicate an editor rather than
              principal creator of a work.</p>
            </xsd:documentation>
          </xsd:annotation>
          <xsd:complexType>
            <xsd:simpleContent>
              <xsd:extension base="text">
                <xsd:attribute name="lang" type="iso639-3" use="optional"/>
                <xsd:attribute name="type" use="optional">
                  <xsd:simpleType>
                    <xsd:restriction base="xsd:string">
                      <xsd:enumeration value="editor"/>
                    </xsd:restriction>
                  </xsd:simpleType>
                </xsd:attribute>
              </xsd:extension>
            </xsd:simpleContent>
          </xsd:complexType>
        </xsd:element>

        <xsd:element name="publication" minOccurs="0" maxOccurs="unbounded">
          <xsd:annotation>
            <xsd:documentation>
              <p>Use this element to include a statement of publication.
              It is intended to correspond roughtly to the MARC 260
              field.</p>
            </xsd:documentation>
          </xsd:annotation>
          <xsd:complexType>
            <xsd:simpleContent>
              <xsd:extension base="text">
                <xsd:attribute name="lang" type="iso639-3" use="optional"/>
              </xsd:extension>
            </xsd:simpleContent>
          </xsd:complexType>
        </xsd:element>

        <xsd:element name="subject" minOccurs="0" maxOccurs="unbounded">
          <xsd:annotation>
            <xsd:documentation>
              <p>This element is used to describe a subject heading,
              keyword, or other tag describing the subject coverage of the
              object. An optional lang attribute may be used to indicate
              the language of the subject heading. They should be used with
              values of "eng" and "fra" if subject elements are included
              for both languages, but ommitted otherwise. Subjects tagged
              with one language may only display in bibliographic records
              for that user interface language (though they will be
              searchable irrespective of interface language).</p>
            </xsd:documentation>
          </xsd:annotation>
          <xsd:complexType>
            <xsd:simpleContent>
              <xsd:extension base="text">
                <xsd:attribute name="lang" type="iso639-3" use="optional"/>
              </xsd:extension>
            </xsd:simpleContent>
          </xsd:complexType>
        </xsd:element>

        <xsd:element name="note" minOccurs="0" maxOccurs="unbounded">
          <xsd:annotation>
            <xsd:documentation>
              <p>The not element is used for general notes and information
              that does not fit elsewhere. The type attribute may be used
              to indicate the type of note.</p>
            </xsd:documentation>
          </xsd:annotation>
          <xsd:complexType>
            <xsd:simpleContent>
              <xsd:extension base="text">
                <xsd:attribute name="lang" type="iso639-3" use="optional"/>
                <xsd:attribute name="type" use="optional">
                  <xsd:simpleType>
                    <xsd:restriction base="xsd:string">
                      <xsd:enumeration value="continued"/>
                      <xsd:enumeration value="continues"/>
                      <xsd:enumeration value="extent"/>
                      <xsd:enumeration value="frequency"/>
                      <xsd:enumeration value="identifier"/>
                      <xsd:enumeration value="missing"/>
                      <xsd:enumeration value="rights"/>
                      <xsd:enumeration value="source"/>
                    </xsd:restriction>
                  </xsd:simpleType>
                </xsd:attribute>
              </xsd:extension>
            </xsd:simpleContent>
          </xsd:complexType>
        </xsd:element>

        <xsd:element name="descriptor" minOccurs="0" maxOccurs="unbounded">
          <xsd:annotation>
            <xsd:documentation>
              <p>This element may be used to enter descriptive terms. They
              should be from a controlled vocabulary. The type attribute
              may be used to indicate the type of descriptor. Otherwise,
              descriptors are similar to subjects.</p>
            </xsd:documentation>
          </xsd:annotation>
          <xsd:complexType>
            <xsd:simpleContent>
              <xsd:extension base="text">
                <xsd:attribute name="lang" type="iso639-3" use="optional"/>
                <xsd:attribute name="type" use="optional">
                  <xsd:simpleType>
                    <xsd:restriction base="xsd:string">
                      <xsd:enumeration value="corporate"/>
                      <xsd:enumeration value="date"/>
                      <xsd:enumeration value="location"/>
                      <xsd:enumeration value="person"/>
                    </xsd:restriction>
                  </xsd:simpleType>
                </xsd:attribute>
              </xsd:extension>
            </xsd:simpleContent>
          </xsd:complexType>
        </xsd:element>

        <xsd:element name="text" minOccurs="0" maxOccurs="unbounded">
          <xsd:annotation>
            <xsd:documentation>
              <p>The text attribute is used to record large blocks of
              textual content. The lang attribute may be used to indicate
              the language of the text. The type attribute should be used
              if applicable. Allowed values for type are "content" which
              is used to indicate that the text is taken from the object
              itself (e.g. OCR text) or "description" which is used to
              indicate that the text is provided by an external source but
              describes or comments upon the object.</p>
            </xsd:documentation>
          </xsd:annotation>
          <xsd:complexType>
            <xsd:simpleContent>
              <xsd:extension base="text">
                <xsd:attribute name="lang" type="iso639-3" use="optional"/>
                <xsd:attribute name="type" use="optional">
                  <xsd:simpleType>
                    <xsd:restriction base="xsd:string">
                      <xsd:enumeration value="content"/>
                      <xsd:enumeration value="description"/>
                    </xsd:restriction>
                  </xsd:simpleType>
                </xsd:attribute>
              </xsd:extension>
            </xsd:simpleContent>
          </xsd:complexType>
        </xsd:element>
        
    </xsd:choice>
  </xsd:group>

  <!-- Types -->

  <xsd:complexType name="resource">
    <xsd:simpleContent>
      <xsd:extension base="text">
        <xsd:attribute name="mime" type="mime" use="required"/>
        <xsd:attribute name="size" type="xsd:positiveInteger" use="optional"/>
        <xsd:attribute name="md5" type="md5digest" use="optional"/>
      </xsd:extension>
    </xsd:simpleContent>
  </xsd:complexType>

  <xsd:simpleType name="iso639-3">
    <xsd:restriction base="xsd:string">
      <xsd:pattern value="[a-z]{3}"/>
    </xsd:restriction>
  </xsd:simpleType>

  <xsd:simpleType name="iso8601">
    <xsd:restriction base="xsd:dateTime">
      <xsd:pattern value="[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9]{2}:[0-9]{2}:[0-9]{2}\.[0-9]{3}Z"/>
    </xsd:restriction>
  </xsd:simpleType>

  <xsd:simpleType name="key">
    <xsd:restriction base="xsd:string">
      <xsd:pattern value="[A-Za-z0-9_.-]{1,127}"/>
    </xsd:restriction>
  </xsd:simpleType>

  <xsd:complexType name="group">
    <xsd:simpleContent>
      <xsd:extension base="key">
        <xsd:attribute name="type" type="xsd:string" use="required"/>
      </xsd:extension>
    </xsd:simpleContent>
  </xsd:complexType>

  <xsd:simpleType name="text">
    <xsd:restriction base="xsd:string">
      <xsd:minLength value="1"/>
    </xsd:restriction>
  </xsd:simpleType>

  <xsd:simpleType name="lcalpha">
    <xsd:restriction base="xsd:string">
      <xsd:pattern value="[a-z]+"/>
    </xsd:restriction>
  </xsd:simpleType>

  <xsd:simpleType name="md5digest">
    <xsd:restriction base="xsd:string">
      <xsd:pattern value="[0-9a-f]{32}"/>
    </xsd:restriction>
  </xsd:simpleType>

  <xsd:simpleType name="mime">
    <xsd:restriction base="xsd:string">
      <xsd:enumeration value="application/pdf"/>
      <xsd:enumeration value="image/jpeg"/>
      <xsd:enumeration value="image/tiff"/>
      <xsd:enumeration value="image/jp2"/>
    </xsd:restriction>
  </xsd:simpleType>

  <xsd:simpleType name="version">
    <xsd:restriction base="xsd:string">
      <xsd:enumeration value="1.0"/>
      <xsd:enumeration value="1.1"/>
      <xsd:enumeration value="1.2"/>
    </xsd:restriction>
  </xsd:simpleType>

</xsd:schema>