<?xml version="1.0" encoding="UTF-8"?>
<xsd:schema xmlns="http://www.crossref.org/schema/3.0.3" xmlns:xsd="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.crossref.org/schema/3.0.3">
	<!--Conforms to w3c http://www.w3.org/2001/XMLSchema-->
	<!-- =============================================================

                          Introduction

     CrossRef DTD Version 3.0.3
     for Journal, book and conferernce submissions

     Developed for CrossRef (www.crossref.org) by

     Inera Incorporated
     Newton, MA 02460
     http://www.inera.com
     email: info@inera.com

     Last Updated September 20, 2004
     (c) 2001-2004 PILA, Inc. All Rights Reserved.

    For more information on the use of this DTD, see
    "CrossRef Schema Documentation 3.0.3.pdf". Also available are sample
    files journal303.xml, book303.xml, conf303.xml, and stand_alone303.xml.

    Document analysis and publisher surveys used to build this schema
    are available on request from CrossRef.

     ============================================================= -->
	<!-- =============================================================

                          File Organization

     This schema is organized into the following sections:
     0. Include module common to multiple CrossRef schemas
     1. Shared attributes
     2. Schema-specific data types
     3. Header Elements
     4. Journal elements
     5. Conference elements
     6. Book elements
     7. Elements common to books and conferences
     8. Elements common to journals, books and conferences

     ============================================================= -->
	<!-- =============================================================

                          Change History

    Changes record version, author initials, date, and comments

    3.0.3.1 (CSK) 10/11/05

    Increased the length of <special_numbering> to 32 characters

    3.0.3 (CSK) 7/20/04

    Added the <component> element to the common include file and to the <journal_article>,
    <conference_paper> and <content_item> elements to allow the deposit of component
    DOIs on their own or as parts of the three higher level entities. Also added
	<sa_component> which identifies a parent DOI that may already exist (e.g. created
	in an earlier deposit or via some other registration process).

    3.0.2 (CSK) 7/16/04

    Extensively modified collection element to fit multiple resolution pilot/demo. Added <doi> to the
    possible elements in <item>

    Moved elments resource,item,collection,property_t and property from the
    main schema file to include file (common1.0.2.xsd) to faciliate creating a schema
    for the deposit of only multiple resolution data.

    3.0.1 (CSK)  4/12/04

    Increased version number to reflect changes made in the common file.

    3.0.0 (BDR) 11/05/03 (CSK) 12/19/03

    Added citation_list element to support deposits of reference lists in journal
    articles for forward linking

    Separated common elements for reuse in other CrossRef schemas into common.xsd

    2.0.7 (HS) Made DOI and contributors elements under book_metadata optional (to accommodate Elsevier)

    2.0.6.1 (CSK) set min values to zero for <conference_date> and <conference_location> under
                  the <event_metadata> record

    2.0.5.2 (CSK) 9/02/03 changed the datatype for DOI and RESOURCE back to String from anyURI

    2.0.5.1 (CSK) 3/19/03 increased number of allowed contributors to "unbounded"

    2.0.5 (CSK) 10/04/02 minor change, fully backward compatible

    Modifed xrefMonth maxInclusive value to "34" to allow extended definitions

    2.0.5 (BDR) 05/02/02

    Brought into full conformance with Xerces 2.0

    2.0.4 (BDR) 02/25/02

    Changed default name space declaration and brought into full
    conformance with XML Spy 4.3

    2.0.3 (BDR) 01/18/02

    Changed item_data to resource and property where resource is the
    container for a URI related to a DOI and property elements
    qualify the resource or collection to which    they're applied.

    Changed data type of DOI from string to xsd:anyURI

    Changed the relationship of item and collection.

    2.0.2 (BDR) 01/15/02

    Tightened validation of ISBN and ISSN instances

    Changed item_number maxLength from 15 to 32, added an
    attribute for item_number_type, and changed publisher_item
    to allow up to three item_number elements.

    Added face markup to title, original_language_title, and subtitle
    elements. This addition allows basic face markup in titles for
    those disciplines (e.g. in genetics, mathematics) where lack of
    face markup can result in ambiguous interpretation.

    Increased DOI maxLength from 255 to 2048 characters

    Changed the doi_data model from url to collection, item and item_data
    to allow future expansion for multiple resolution. WARNING: the
    collection model is infinitely recursive and may only be used in
    accordance with the documentation provide by CrossRef!

    2.0.1 (BDR) 10/25/01

    Added contributors as an optional element to journal_issue to allow
    for cases when a special issue of a journal has editors who may be
    listed when the entire issue is cited

    2.0.0 (BDR) 10/09/01

    First major release of version 2.0.0, based loosely on
    version 0.3 by Howard Ratner.

     ============================================================= -->
	<!-- =============================================================

          0. Include module common to multiple CrossRef schemas

     ============================================================= -->
	<!-- version 1.0 will be a link to the latest 1.0.X version    -->
	<xsd:include schemaLocation="http://www.crossref.org/schema/deposit/common1.0.5.xsd"/>
	<!-- =============================================================

                          1. Shared attributes

     ============================================================= -->
	<!--               Moved to common.xsd for version 3.0.0           -->
	<!-- =============================================================

                     2. Schema-specific data types

     ================================================================= -->
	<!--               Moved to common.xsd for version 3.0.0           -->
	<!-- =============================================================

                          3. Header elements

     ================================================================= -->
	<!--      Most elements moved to common.xsd for version 3.0.0      -->
	<xsd:element name="doi_batch">
		<xsd:complexType>
			<xsd:sequence>
				<xsd:element ref="head"/>
				<xsd:element ref="body"/>
			</xsd:sequence>
			<xsd:attribute name="version" type="xsd:string" fixed="3.0.3"/>
		</xsd:complexType>
	</xsd:element>
	<xsd:element name="head">
		<xsd:complexType>
			<xsd:sequence>
				<xsd:element ref="doi_batch_id"/>
				<xsd:element ref="timestamp"/>
				<xsd:element ref="depositor"/>
				<xsd:element ref="registrant"/>
			</xsd:sequence>
		</xsd:complexType>
	</xsd:element>
	<!-- ===========================================================================
     The top level of the CrossRef deposit schema allows for the deposit of DOIs
     for journals (and their articles), books (and their chapters), conferences
     (and their conference papers). Also supported is the stand alone deposit of DOIs
     for components. However, all components must refer to a parent DOI either implicitly
     when the component is deposited a part of the work metadata (e.g. journal article), or
     explicitly when deposited as a stand alone level element <sa_component>
     directly under the <body> tag .

-->
	<xsd:element name="body">
		<xsd:complexType>
			<xsd:choice>
				<xsd:element ref="journal" maxOccurs="unbounded"/>
				<xsd:element ref="book" maxOccurs="unbounded"/>
				<xsd:element ref="conference" maxOccurs="unbounded"/>
				<xsd:element ref="sa_component" maxOccurs="unbounded"/>
			</xsd:choice>
		</xsd:complexType>
	</xsd:element>
	<!-- =============================================================

                          4. Journal elements

     ============================================================= -->
	<xsd:element name="journal">
		<xsd:complexType>
			<xsd:sequence>
				<xsd:element ref="journal_metadata"/>
				<xsd:element ref="journal_issue" minOccurs="0"/>
				<xsd:element ref="journal_article" minOccurs="0" maxOccurs="unbounded"/>
			</xsd:sequence>
		</xsd:complexType>
	</xsd:element>
	<xsd:element name="journal_metadata">
		<xsd:complexType>
			<xsd:sequence>
				<xsd:element ref="full_title"/>
				<xsd:element ref="abbrev_title" maxOccurs="10"/>
				<xsd:element ref="issn" maxOccurs="6"/>
				<xsd:element ref="coden" minOccurs="0"/>
				<xsd:element ref="doi_data" minOccurs="0"/>
			</xsd:sequence>
			<xsd:attributeGroup ref="language.atts"/>
		</xsd:complexType>
	</xsd:element>
	<!--
    The full title by which a journal is commonly known or cited.
    full_title and abbrev_title must both be submitted if they are identical.
 -->
	<xsd:element name="full_title">
		<xsd:simpleType>
			<xsd:restriction base="xsd:string">
				<xsd:maxLength value="255"/>
				<xsd:minLength value="1"/>
			</xsd:restriction>
		</xsd:simpleType>
	</xsd:element>
	<!--
    The abbreviated title(s) by which a journal is commonly cited.
    It is preferred, but not required, that periods be included after
    abbreviated words within the title.
 -->
	<xsd:element name="abbrev_title">
		<xsd:simpleType>
			<xsd:restriction base="xsd:string">
				<xsd:maxLength value="150"/>
				<xsd:minLength value="1"/>
			</xsd:restriction>
		</xsd:simpleType>
	</xsd:element>
	<xsd:element name="journal_issue">
		<xsd:complexType>
			<xsd:sequence>
				<xsd:element ref="contributors" minOccurs="0"/>
				<xsd:element ref="publication_date" maxOccurs="10"/>
				<xsd:element ref="journal_volume" minOccurs="0"/>
				<xsd:element ref="issue" minOccurs="0"/>
				<xsd:element ref="special_numbering" minOccurs="0"/>
				<xsd:element ref="doi_data" minOccurs="0"/>
			</xsd:sequence>
		</xsd:complexType>
	</xsd:element>
	<!--
    The container for the journal volume and DOI number assigned to an
    entire journal volume.
 -->
	<xsd:element name="journal_volume">
		<xsd:complexType>
			<xsd:sequence>
				<xsd:element ref="volume"/>
				<xsd:element ref="publisher_item" minOccurs="0"/>
				<xsd:element ref="doi_data" minOccurs="0"/>
			</xsd:sequence>
		</xsd:complexType>
	</xsd:element>
	<!--
    Issue level numbering for supplements or special issues.

    Text defining the type of special issue (e.g. "suppl") should
    be included in this element along with the number.
 -->
	<xsd:element name="special_numbering">
		<xsd:simpleType>
			<xsd:restriction base="xsd:string">
				<xsd:maxLength value="32"/>
				<xsd:minLength value="1"/>
			</xsd:restriction>
		</xsd:simpleType>
	</xsd:element>
	<!--
    A journal article is required to have title and doi_data. All other
    information is optional. When registering items that do not have
    titles, use the appropriate heading from the journal section or
    table of contents (e.g. "Errata") in title.

    journal_article allows for multiple titles per item. In some cases
    it may be helpful to submit multiple titles. For example, if an
    erratum carries title of the original article and the heading "Errata",
    both should be submitted by using two titles elements.
 -->
	<xsd:element name="journal_article">
		<xsd:complexType>
			<xsd:sequence>
				<xsd:element ref="titles" maxOccurs="20"/>
				<xsd:element ref="contributors" minOccurs="0"/>
				<xsd:element ref="publication_date" maxOccurs="10"/>
				<xsd:element ref="pages" minOccurs="0"/>
				<xsd:element ref="publisher_item" minOccurs="0"/>
				<xsd:element ref="doi_data"/>
				<xsd:element ref="citation_list" minOccurs="0"/>
				<xsd:element ref="component_list" minOccurs="0"/>
			</xsd:sequence>
			<xsd:attributeGroup ref="publication_type.atts"/>
			<xsd:attributeGroup ref="language.atts"/>
		</xsd:complexType>
	</xsd:element>
	<!-- =============================================================

                          5. Conference elements

     ============================================================= -->
	<!--
    conference is the core container for information about a single
    conference and its proceedings.

    If a conference proceedings spans multiple volumes, each volume
    must be contained in a unique conference element.
    -->
	<xsd:element name="conference">
		<xsd:complexType>
			<xsd:sequence>
				<xsd:element ref="contributors" minOccurs="0"/>
				<xsd:element ref="event_metadata"/>
				<xsd:element ref="proceedings_metadata"/>
				<xsd:element ref="conference_paper" minOccurs="0" maxOccurs="unbounded"/>
			</xsd:sequence>
		</xsd:complexType>
	</xsd:element>
	<!--
    event_metadata captures information about a conference event. Data
    about conference proceedings is captured in proceedings_metadata.
    -->
	<xsd:element name="event_metadata">
		<xsd:complexType>
			<xsd:sequence>
				<xsd:element ref="conference_name"/>
				<xsd:element ref="conference_theme" minOccurs="0"/>
				<xsd:element ref="conference_acronym" minOccurs="0"/>
				<xsd:element ref="conference_sponsor" minOccurs="0" maxOccurs="10"/>
				<xsd:element ref="conference_number" minOccurs="0"/>
				<xsd:element ref="conference_location" minOccurs="0"/>
				<xsd:element ref="conference_date" minOccurs="0"/>
			</xsd:sequence>
		</xsd:complexType>
	</xsd:element>
	<!--
    conference_name does not include "Proceedings of". For example,
    "The 23rd Annual Meeting of the American Society for Information Science"
    is a correct conference name. It is quite common for a conference name to
    include the conference number. When the number appears in the name, it
    should be included in this element.
    -->
	<xsd:element name="conference_name">
		<xsd:simpleType>
			<xsd:restriction base="xsd:string">
				<xsd:maxLength value="512"/>
				<xsd:minLength value="3"/>
			</xsd:restriction>
		</xsd:simpleType>
	</xsd:element>
	<!--
    The theme is the slogan of the conference. It typically changes from
    conference to conference, e.g. "Knowledge Innovations"
 -->
	<xsd:element name="conference_theme">
		<xsd:simpleType>
			<xsd:restriction base="xsd:string">
				<xsd:maxLength value="255"/>
				<xsd:minLength value="1"/>
			</xsd:restriction>
		</xsd:simpleType>
	</xsd:element>
	<!--
    The popularly known as or jargon name (e.g. SIGGRAPH for "Special
    Interest Group on Computer Graphics").

    The conference acronym often includes the year of the conference
    (e.g. SGML '97) or, less often, the conference number. It is preferred,
    but not required, that submission of metadata exclude number or year
    information from the conference acronym. It is better to include such
    information in conference_number, or conference_date, respectively.
 -->
	<xsd:element name="conference_acronym">
		<xsd:simpleType>
			<xsd:restriction base="xsd:string">
				<xsd:maxLength value="127"/>
				<xsd:minLength value="1"/>
			</xsd:restriction>
		</xsd:simpleType>
	</xsd:element>
	<!--
    The sponsoring organization(s) of a conference. Multiple sponsors may be
    given if a conference is hosted by more than one organization.
 -->
	<xsd:element name="conference_sponsor">
		<xsd:simpleType>
			<xsd:restriction base="xsd:string">
				<xsd:maxLength value="255"/>
				<xsd:minLength value="1"/>
			</xsd:restriction>
		</xsd:simpleType>
	</xsd:element>
	<!--
    conference_number should include only the number of the conference without
    any extra text. For example, "The 24th Annual Conference on" should be
    tagged as <conference_number>24</conference_number>, and "th" should not be
    included.

    When a conference is named such that the year of the conference indicates
    the number (e.g. "SGML 1994"), the year appears in conference_name,
    conference_date, and conference_number, as in:

    <conference_name>SGML 1994</conference_name>
    <conference_acronym>SGML</conference_acronym>
    <conference_number>1994</conference_number>
    <conference_date start_day="07" start_month="11" start_year="1994" end_day="10"
         end_month="11" end_year="1994">November 7-10, 1994<conference_date>
 -->
	<xsd:element name="conference_number">
		<xsd:simpleType>
			<xsd:restriction base="xsd:string">
				<xsd:maxLength value="15"/>
				<xsd:minLength value="1"/>
			</xsd:restriction>
		</xsd:simpleType>
	</xsd:element>
	<!--
    The city and country of the conference. If the conference is in the United
    States, the appropriate state should also be provided, and the country may
    be omitted. The specific venue or address within a city (e.g. conference
    center, hotel, etc.) should not be provided.
 -->
	<xsd:element name="conference_location">
		<xsd:simpleType>
			<xsd:restriction base="xsd:string">
				<xsd:maxLength value="255"/>
				<xsd:minLength value="2"/>
			</xsd:restriction>
		</xsd:simpleType>
	</xsd:element>
	<!--
    conference_date may be used in three ways:

    1. If publishers that do not have parsed date values, they provide just text
    with the conference dates. The date text should be taken from the proceedings
    title page.

    2. If publishers do have parsed date values, they should provide them in the
     attributes.

    3. If both parsed date values and the date text are available, both should be
    provided. This is the preferred tagging for conference_date. For example:

    <conference_date start_month="01" start_year="1997" start_day="15"
        end_year="1997" end_month="01" end_day="17">Jan. 15-17, 1997</conference_date>
 -->
	<xsd:simpleType name="conference_date_t">
		<xsd:restriction base="xsd:string">
			<xsd:maxLength value="100"/>
			<xsd:minLength value="0"/>
		</xsd:restriction>
	</xsd:simpleType>
	<xsd:element name="conference_date">
		<xsd:complexType>
			<xsd:simpleContent>
				<xsd:extension base="conference_date_t">
					<xsd:attribute name="start_day" type="xrefDay" use="optional"/>
					<xsd:attribute name="start_month" type="xrefMonth" use="optional"/>
					<xsd:attribute name="start_year" type="xrefYear" use="optional"/>
					<xsd:attribute name="end_day" type="xrefDay" use="optional"/>
					<xsd:attribute name="end_month" type="xrefMonth" use="optional"/>
					<xsd:attribute name="end_year" type="xrefYear" use="optional"/>
				</xsd:extension>
			</xsd:simpleContent>
		</xsd:complexType>
	</xsd:element>
	<!--
    proceedings_metadata captures information about conference proceedings. Data about
    conference events is captured in event_metadata
 -->
	<xsd:element name="proceedings_metadata">
		<xsd:complexType>
			<xsd:sequence>
				<xsd:element ref="proceedings_title"/>
				<xsd:element ref="proceedings_subject" minOccurs="0"/>
				<xsd:element ref="publisher" maxOccurs="5"/>
				<xsd:element ref="publication_date" maxOccurs="10"/>
				<xsd:element ref="volume" minOccurs="0"/>
				<xsd:element ref="series_metadata" minOccurs="0"/>
				<xsd:element ref="isbn" minOccurs="0" maxOccurs="6"/>
				<xsd:element ref="issn" minOccurs="0" maxOccurs="6"/>
				<xsd:element ref="coden" minOccurs="0"/>
				<xsd:element ref="publisher_item" minOccurs="0"/>
				<xsd:element ref="doi_data" minOccurs="0"/>
			</xsd:sequence>
			<xsd:attributeGroup ref="language.atts"/>
		</xsd:complexType>
	</xsd:element>
	<!--
    The title of the conference proceedings as printed on title page of the published
    conference proceedings.

    In some cases, proceedings_title may differ from conference_name only in that the
    text "Proceedings of" often appears at the start of the proceedings_title, and it
    this text should never be included in conference_name. In other cases, the
    proceedings_title and conference_name may be quite different.
 -->
	<xsd:element name="proceedings_title">
		<xsd:simpleType>
			<xsd:restriction base="xsd:string">
				<xsd:maxLength value="511"/>
				<xsd:minLength value="1"/>
			</xsd:restriction>
		</xsd:simpleType>
	</xsd:element>
	<!--
    The subject of the printed conference proceedings, e.g. "Computer Graphics" is the
    subject matter of SIGGRAPH.

    This element is useful because an author may cite a conference paper by the conference
    subject. For example, "Proceedings of the 1999 ACM Conference on Computer Graphics".
 -->
	<xsd:element name="proceedings_subject">
		<xsd:simpleType>
			<xsd:restriction base="xsd:string">
				<xsd:maxLength value="255"/>
				<xsd:minLength value="1"/>
			</xsd:restriction>
		</xsd:simpleType>
	</xsd:element>
	<!--
    This element is useful because an author may cite a conference paper by the conference
    subject. For example, "Proceedings of the 1999 ACM Conference on Computer Graphics"
 -->
	<xsd:element name="conference_paper">
		<xsd:complexType>
			<xsd:sequence>
				<xsd:element ref="contributors"/>
				<xsd:element ref="titles"/>
				<xsd:element ref="publication_date" minOccurs="0" maxOccurs="10"/>
				<xsd:element ref="pages" minOccurs="0"/>
				<xsd:element ref="publisher_item" minOccurs="0"/>
				<xsd:element ref="doi_data"/>
				<xsd:element ref="component_list" minOccurs="0"/>
			</xsd:sequence>
			<xsd:attributeGroup ref="publication_type.atts"/>
			<xsd:attributeGroup ref="language.atts"/>
		</xsd:complexType>
	</xsd:element>
	<!-- =============================================================

                          6. Book elements

     ============================================================= -->
	<!--
    book is the core container for information about a specific book.
    Books may be in the form of edited books (i.e. a contributed volume with one or
    more editors), monographs (single-authored works), or reference works (e.g. encyclopedias)

    If a book contains multiple volumes, each volume must be contained in a unique book element.

    You may chose to submit only top level contributors and book_metadata for any book, or
    you may chose to submit these elements along with metadata for each content_item. A content
    item is typically any item that is listed on the table of contents such as a chapter,
    section, etc. It is not necessary to submit metadata for all items listed on the table of
    contents. You may chose to drop items of lesser significance such as front and back matter.
 -->
	<xsd:element name="book">
		<xsd:complexType>
			<xsd:sequence>
				<xsd:element ref="book_metadata"/>
				<xsd:element ref="content_item" minOccurs="0" maxOccurs="unbounded"/>
			</xsd:sequence>
			<xsd:attribute name="book_type" use="required">
				<xsd:simpleType>
					<xsd:restriction base="xsd:NMTOKEN">
						<xsd:enumeration value="edited_book"/>
						<xsd:enumeration value="monograph"/>
						<xsd:enumeration value="reference"/>
						<xsd:enumeration value="other"/>
					</xsd:restriction>
				</xsd:simpleType>
			</xsd:attribute>
		</xsd:complexType>
	</xsd:element>
	<!--
    The language of the book should be specified in the book_metadata language attribute.
    If a book contains items in multiple languages this attribute should be set for the
    predominant language of the book. Individual items may have their language specified
    in the content_item. If all content items are the same language, it is only necessary
    to specify the language of the book in this element.

    The contributors are the author(s) or editor(s) of the entire work. If a multi-volume
    work has separate editors for each volume, those editors should be specified in this
    element, and the series editors are listed in the series_metadata contributors.

    Books may have their title specified in one of two ways. For a monograph or single
    volume work, you should use titles in book_metadata. If a work spans multiple volumes,
    you should use titles in series_metadata. If a work spans multiple volumes with a unique
    title for each volume and the whole series, you should specify the series title in
    titles in series_metadata and the volume title in titles in book_metadata.

    Up to 6 titles or series_metadata may be used per book_metadata, however in practice
    there should not be more than one series_metadata per book_metadata, and only in rare
    situations should there be more than one titles per book_metadata.

    volume and edition_number, when given, should include only a number and not additional
    text such as "volume" or "edition". For example, you should submit "3", not "third edition".

    For a monograph or single volume work, you should use isbn in book_metadata. If a work
    spans multiple volumes, you should use isbn in series_metadata. If a work spans multiple
    volumes with a unique ISBN for each volume and the whole series, you should specify the
    series ISBN in sibn in series_metadata and the volume ISBN in isbn in book_metadata.

    publisher_item, when given, specifies this information for the entire book or volume.
    This element also appears in content_item.

    doi_data is required for each book or volume that you submit. It is not possible to
    submit DOI information for individual chapters without assigning a DOI to the entire work.

    WARNING:  Care must be taken when submitting books with series. If a series title is
    submitted and no book title is supplied but an ISBN is supplied at the book_metadata level
    and not with the series title, the CrossRef system will index a series title with no ISBN
    and an ISBN with no title. Please take care to associate the ISBN (or ISSN) at the correct
    level of the XML hierarchy!
 -->
	<xsd:element name="book_metadata">
		<xsd:complexType>
			<xsd:sequence>
				<xsd:element ref="contributors" minOccurs="0"/>
                <xsd:choice maxOccurs="6">
                    <xsd:element ref="series_metadata"/>
                    <xsd:element ref="titles"/>
                </xsd:choice>				<xsd:element ref="volume" minOccurs="0"/>
				<xsd:element ref="edition_number" minOccurs="0"/>
				<xsd:element ref="publication_date" maxOccurs="10"/>
				<xsd:element ref="isbn" minOccurs="0" maxOccurs="6"/>
				<xsd:element ref="issn" minOccurs="0" maxOccurs="6"/>
				<xsd:element ref="publisher"/>
				<xsd:element ref="publisher_item" minOccurs="0"/>
				<xsd:element ref="doi_data" minOccurs="0"/>
			</xsd:sequence>
			<xsd:attributeGroup ref="language.atts"/>
		</xsd:complexType>
	</xsd:element>
	<!--
    A content item is typically an item listed on the table of contents for a book.
    There need not be a one-to-one correlation between content listings and content items
    (e.g. you may choose not to register front and back matter items listed in the table
    of contents).

    The language of a content_item only need be set if it differs from the language of book_metadata.

    The component_type indicates the type of content item you are registering.

    level_sequence_number indicates the level of nesting for content items. For example,
    you may use it to indicate when one content item, such as a chapter, is actually
    inside another content item, such as a section. Please see the example of a book
    submission in this documentation for a better understanding of how this item may
    be used in nested tables of contents.

    Note: Because the CrossRef schema uses a flat model to indicate hierarchically nested
    content items, there is an implicit assumption that content items will be listed in the
    CrossRef submission in the same order in which they appear in the table of contents.
    Please follow this protocol when submitting DOI data.

    contributors for a content_item need not be listed if all items in a book have the same
    contributors listed in book_metadata. In other words, contributors must be listed for
    edited books, but they should not be listed for each content_item in a monograph. The
    exception case is when a content item such as a Preface or Forward for a monograph has
    a different author from that of the monograph. In this case, the contributors should be given.

    The title of each content item must be submitted. If, however, you are submitted data for
    a monograph that simply has "Chapter 1", "Chapter 2", etc., you should put this information
    in component_number, not titles.
 -->
	<xsd:element name="content_item">
		<xsd:complexType>
			<xsd:sequence>
				<xsd:element ref="contributors" minOccurs="0"/>
				<xsd:element ref="titles" minOccurs="0"/>
				<xsd:element ref="component_number" minOccurs="0"/>
				<xsd:element ref="publication_date" minOccurs="0" maxOccurs="10"/>
				<xsd:element ref="pages" minOccurs="0"/>
				<xsd:element ref="publisher_item" minOccurs="0"/>
				<xsd:element ref="doi_data"/>
				<xsd:element ref="component_list" minOccurs="0"/>
			</xsd:sequence>
			<xsd:attribute name="component_type" use="required">
				<xsd:simpleType>
					<xsd:restriction base="xsd:NMTOKEN">
						<xsd:enumeration value="chapter"/>
						<xsd:enumeration value="section"/>
						<xsd:enumeration value="part"/>
						<xsd:enumeration value="track"/>
						<xsd:enumeration value="reference_entry"/>
						<xsd:enumeration value="other"/>
					</xsd:restriction>
				</xsd:simpleType>
			</xsd:attribute>
			<xsd:attribute name="level_sequence_number" default="1">
				<xsd:simpleType>
					<xsd:restriction base="xsd:positiveInteger">
						<xsd:maxInclusive value="9"/>
						<xsd:minInclusive value="1"/>
						<xsd:totalDigits value="1"/>
					</xsd:restriction>
				</xsd:simpleType>
			</xsd:attribute>
			<xsd:attributeGroup ref="publication_type.atts"/>
			<xsd:attributeGroup ref="language.atts"/>
		</xsd:complexType>
	</xsd:element>
	<!-- =============================================================

              7. Elements common to books and conferences

     ============================================================= -->
	<!--
    When a book or conference proceedings consists of multiple volumes,
    series_metadata is used to describe information about the entire series.
 -->
	<xsd:element name="series_metadata">
		<xsd:complexType>
			<xsd:sequence>
				<xsd:element ref="titles"/>
				<xsd:element ref="contributors" minOccurs="0"/>
				<xsd:element ref="isbn" minOccurs="0" maxOccurs="6"/>
				<xsd:element ref="series_number" minOccurs="0"/>
				<xsd:element ref="publisher_item" minOccurs="0"/>
				<xsd:element ref="doi_data" minOccurs="0"/>
			</xsd:sequence>
		</xsd:complexType>
	</xsd:element>
	<!--
    The series number is different from the volume number. A volume number is expected
    to be the number of a book in a physically printed set and typically appears in sequence.
    The series number is not tied to the physical manifestation of the printed volume
    and need not be strictly in sequence.

    This element is available in series_metadata, however it should only be used for
    conference proceedings and not for books.
 -->
	<xsd:element name="series_number">
		<xsd:simpleType>
			<xsd:restriction base="xsd:string">
				<xsd:maxLength value="15"/>
				<xsd:minLength value="1"/>
			</xsd:restriction>
		</xsd:simpleType>
	</xsd:element>
	<xsd:element name="publisher">
		<xsd:complexType>
			<xsd:sequence>
				<xsd:element ref="publisher_name"/>
				<xsd:element ref="publisher_place" minOccurs="0"/>
			</xsd:sequence>
		</xsd:complexType>
	</xsd:element>
	<!--
    publisher_place gives the primary city location of the publisher. When the location
    is a major city (e.g. New York, Amsterdam), no qualifying country or U.S. state need
    be given. If the city is not a major city, the appropriate country or U.S. state
    should be added.
 -->
	<xsd:element name="publisher_place">
		<xsd:simpleType>
			<xsd:restriction base="xsd:string">
				<xsd:maxLength value="255"/>
				<xsd:minLength value="2"/>
			</xsd:restriction>
		</xsd:simpleType>
	</xsd:element>
	<!--
    The name of the publisher of a book or conference proceedings.

    publisher_name is the imprint of the publication (what the author will likely cite),
    not the organization registering the DOI, if for any reason they are different.
 -->
	<xsd:element name="publisher_name">
		<xsd:simpleType>
			<xsd:restriction base="xsd:string">
				<xsd:maxLength value="255"/>
				<xsd:minLength value="1"/>
			</xsd:restriction>
		</xsd:simpleType>
	</xsd:element>
	<!-- =============================================================

       8. Elements common to journals, books and conferences

     ============================================================= -->
	<!--
    The next few elements allow an item to be tied to publisher internal
    identifiers. item_number and identifier are publisher-assigned numbers
    that uniquely identify the item being registered.

    item_number should be used for identifiers based on publisher internal
    standards. identifier should be used for identifiers based on a public standard.

    If the item_number and identifier are identical, there is no need to submit
    both. In this case, the preferred element to use is identifier.

    item_number within publisher_item can be used to reduce the occurrence
    of conflicts when the metadata for a DOI may not adequately distinguish the
    DOI from that of another DOI. By setting the attribute to
    <item_number item_number_type="sequence-number"> and by providing a unique
    value for <item_number> the CrossRef system will not generate a deposit conflict.
    Often it is acceptable to use the DOI or its suffix for this unique value.

    For more information see: http://www.crossref.org/02publishers/how_to_faq.html#Anchor-Dealin-60673
 -->
	<xsd:element name="publisher_item">
		<xsd:complexType>
			<xsd:sequence>
				<xsd:element ref="item_number" minOccurs="0" maxOccurs="3"/>
				<xsd:element ref="identifier" minOccurs="0" maxOccurs="10"/>
			</xsd:sequence>
		</xsd:complexType>
	</xsd:element>
	<!--
    item_number is a publisher-assigned number that uniquely identifies the entity
    being registered.

    item_number  should be used for identifiers based on publisher internal standards.
    Use identifier for a publisher identifier that is based on a public standard such
    as PII or SICI.

    If the item_number and identifier are identical, there is no need to submit both.
    In this case, the preferred element to use is identifier.

    Data may be alpha, numeric or a combination.

    item_number has an optional attribute, item_number_type. It is assigned by the
    publisher to provide context for the data in item_number. If item_number contains
    only a publisher's tracking number, this attribute need not be supplied.
    If the item_number contains other data, this attribute can be used to define the content.
    For example, if a journal is published online (i.e. it has no page numbers), and each
    article on the table of contents is assigned a sequential number, this article number
    can be placed in item_number, and the item_number_type attribute can be set to
    "article_number". Although CrossRef has not provided a set of enumerated types for this
    attribute, please check with CrossRef before using this attribute to determine if a
    standard attribute has already been defined for your specific needs.
 -->
	<xsd:simpleType name="item_number_t">
		<xsd:restriction base="xsd:string">
			<xsd:maxLength value="32"/>
			<xsd:minLength value="1"/>
		</xsd:restriction>
	</xsd:simpleType>
	<xsd:element name="item_number">
		<xsd:complexType>
			<xsd:simpleContent>
				<xsd:extension base="item_number_t">
					<xsd:attribute name="item_number_type" type="xsd:string" use="optional"/>
				</xsd:extension>
			</xsd:simpleContent>
		</xsd:complexType>
	</xsd:element>
	<xsd:simpleType name="identifier_t">
		<xsd:restriction base="xsd:string">
			<xsd:maxLength value="255"/>
			<xsd:minLength value="1"/>
		</xsd:restriction>
	</xsd:simpleType>
	<xsd:element name="identifier">
		<xsd:complexType>
			<xsd:simpleContent>
				<xsd:extension base="identifier_t">
					<xsd:attribute name="id_type" use="required">
						<xsd:simpleType>
							<xsd:restriction base="xsd:NMTOKEN">
								<xsd:enumeration value="pii"/>
								<xsd:enumeration value="sici"/>
								<xsd:enumeration value="doi"/>
								<xsd:enumeration value="other"/>
							</xsd:restriction>
						</xsd:simpleType>
					</xsd:attribute>
				</xsd:extension>
			</xsd:simpleContent>
		</xsd:complexType>
	</xsd:element>
</xsd:schema>
