<!-- ============================================================= -->
<!--  MODULE:    Link Element Classes                              -->
<!--  VERSION:   2.3                                               -->
<!--  DATE:      February 2007                                     -->
<!--                                                               -->
<!-- ============================================================= -->


<!-- ============================================================= -->
<!--                    PUBLIC DOCUMENT TYPE DEFINITION            -->
<!--                        TYPICAL INVOCATION                     -->
<!--
"-//NLM//DTD Archiving and Interchange DTD Suite Link Class Elements v2.3 20070202//EN"
     Delivered as file "link.ent"                                  -->
<!-- ============================================================= -->


<!-- ============================================================= -->
<!-- SYSTEM:     Archiving and Interchange DTD Suite               -->
<!--                                                               -->
<!-- PURPOSE:    Names all elements in the link class. These are   --> 
<!--             elements that are links (internal or external)    -->
<!--             by definition, such as URLs <uri> and             -->
<!--             Cross(X)-references <xref>.                       -->
<!--                                                               -->
<!-- CONTAINS:   1) Default definitions of the link classes        -->
<!--             2) Default definitions for attribute values       -->
<!--             3) Default definitions for attribute lists        -->
<!--             4) Models for the link class elements, first      -->
<!--             internal links then external links                -->
<!--             (alphabetically)                                  -->
<!--                                                               -->
<!--             (Note: Links make their links using the XLink     -->
<!--             global attributes. Many elements besides          -->
<!--             explicit links may be made into links using       -->
<!--             these attributes. Such elements are defined in    -->
<!--             the module appropriate to their use and are not   -->
<!--             listed here.)                                     -->
<!--                                                               -->
<!-- CREATED FOR:                                                  -->
<!--             Digital archives and publishers who wish to       -->
<!--             create a custom XML DTD for original markup of    -->
<!--             journal literature, books, and related material,  -->
<!--             or for archiving and transferring such material   -->
<!--             between archives.                                 -->
<!--                                                               -->
<!--             This DTD is in the public domain. An organization -->
<!--             that wishes to create its own DTD from the suite  -->
<!--             may do so without permission from NLM.            -->
<!--                                                               -->
<!--             The suite has been set up to be extended using a  -->
<!--             new DTD file and a new DTD-specific customization -->
<!--             module to redefine the many Parameter Entities.   -->
<!--             Do not modify the suite directly or redistribute  -->
<!--             modified versions of the suite.                   -->
<!--                                                               -->
<!--             In the interest of maintaining consistency and    -->
<!--             clarity for potential users, NLM requests:        -->
<!--                                                               -->
<!--             1. If you create a DTD from the Archiving and     -->
<!--                Interchange DTD Suite and intend to stay       -->
<!--                compatible with the suite, then please include -->
<!--                the following statement as a comment in all of -->
<!--                your DTD modules:                              -->
<!--                   "Created from, and fully compatible with,   -->
<!--                    the Archiving and Interchange DTD Suite."  -->
<!--                                                               -->
<!--             2. If you alter one or more modules of the suite, -->
<!--                then please rename your version and all its    -->
<!--                modules to avoid any confusion with the        -->
<!--                original suite. Also, please include the       -->
<!--                following statement as a comment in all your   -->
<!--                DTD modules:                                   -->
<!--                   "Based in part on, but not fully compatible -->
<!--                    with, the Archiving and Interchange DTD    --> 
<!--                    Suite."                                    -->
<!--                                                               -->
<!--             Suggestions for refinements and enhancements to   -->
<!--             the DTD suite should be sent in email to:         -->
<!--                 archive-dtd@ncbi.nlm.nih.gov                  -->
<!--                                                               -->
<!-- ORIGINAL CREATION DATE:                                       -->
<!--             December 2002                                     -->
<!--                                                               -->
<!-- CREATED BY: Jeff Beck       (NCBI)                            -->
<!--             Deborah Lapeyre (Mulberry Technologies, Inc.)     -->
<!--             Bruce Rosenblum (Inera Inc.)                      -->
<!--                                                               -->
<!--             NLM thanks the Harvard University Libraries, both -->
<!--             for proposing that a draft archiving NLM DTD for  --> 
<!--             life sciences journals be extended to accommodate -->
<!--             journals in all disciplines and for sponsoring    -->
<!--             Bruce Rosenblum's collaboration with other DTD    -->
<!--             authors in completing Version 1.0. The Andrew W.  --> 
<!--             Mellon Foundation provided support for these      --> 
<!--             important contributions.                          -->
<!--                                                               -->
<!-- ============================================================= -->


<!-- ============================================================= -->
<!--                    DTD VERSION/CHANGE HISTORY                 -->
<!-- ============================================================= -->
<!--
     =============================================================

Version  Reason/Occasion                   (who) vx.x (yyyy-mm-dd)

     =============================================================
     Version 2.3                       (DAL/BTU) v2.3 (2007-02-02)
     
     Enhancement Release (2.3) following the Working Group meetings 
     of Oct-Nov/2006-Jan/2007. No backward-incompatible changes.
     Archiving loosened even more. New structures for all the DTDs. 
     
 14. NEW TYPE ATTRIBUTES - Added "content-type" attribute to the
     following elements
     - inline-supplementary-material  
     
 13. NEW PARAMETER ENTITIES - Added parameter entities for the
     attribute lists of:
     - target
     
 12. Updated public identifier to "v2.3 20070202//EN"          

     =============================================================
     Version 2.1                       (DAL/BTU) v2.1 (2005-06-30)
          
     Changed to MathML 2.0 and MathML 2.0 Character Sets
     Added new material requested by NCBI   
          
 11. Minor, non-functional changes to wording in comments as part 
     of 2.1 release.
                    
 10. Updated public identifier to "v2.3 20070202" 

     =============================================================
     Version 2.0                       (DAL/BTU) v2.0 (2004-08-30)
          
     Major requirement changes led to the new release, producing
     DTD version "2.0":
       a) The splitting of the Archival and Interchange Tag Set 
          DTDs into three DTDs from two: an authoring DTD, an
          archive regularization and interchange DTD (the
          current Blue Publishing DTD), and a preservationist 
          archive DTD (the current Green Archiving and Interchange 
          DTD).
       b) AIT Working Group suggestions from the June 04 meeting 
          and June/July 2004 followup discussions
       c) Suite remodularization to meet new (and newly articulated)
          modularization requirements
       d) New or renamed classes and mixes to make modifications
          easier and more consistent

  9. COMPLETE MODELS WHEN OVER-RIDING A MODEL 
     (for all Parameter Entities suffixed "-model")
     ### Customization Alert ###
     Made all the model over-rides consistent. Some included
     the outer parentheses, some did not. They all do now,
     -  %fn-model; 

  8. DEFAULT CLASSES - Were moved from this module to 
     %default-classes.ent;

  7. FOOTNOTE
        - Made model into a Parameter Entity
        - Added optional <label> to the beginning of the model,
          before the paragraphs

  6. To correct potential classing problems, used the following
     new Parameter Entities:
        - %just-para.class; used in <fn> (%fn-model; uses 
          %just-para.class;)

  5. Updated public identifier to "v2.3 20070202"

     =============================================================
     Version 1.1                         (TRG/BTU) v1.1 (2003-11-01)

  4. Added "alternate-form-of", "content-type", and ID attributes 
     to <inline-supplementary-material> (by modifying 
     %inline-supplementary-material-atts;)
     Rationale: To provide parallelism between attributes for 
     <supplementary-material> and <inline-supplementary-material>

  3. Added "mimetype" and "mime-subtype" attributes to 
     <inline-supplementary-material> (as part of adding these 
     attributes to all graphic and multi-media elements)

  2. Added ID attribute information to <xref> (by modifying
     parameter entity %xref-atts;)
     Rationale: Provide unique identifier so <xref>
     element can be linked to (creating two-way link). 

  1. Added an optional "target-type" attribute to element 
     <target>.  Rationale: To identify the reason for this target.
                                                                   -->


<!-- ============================================================= -->
<!--                    PARAMETER ENTITY DEPENDENCIES             
                        Requires the following parameter entities
                        be defined before calling this module, 
                        usually accomplished in the Customization
                        Module for the specific DTD:
                          %access.class;
                          %emphasis.class;
                          %link-elements;
                          %might-link-atts;
                          %subsup.class;
                                                                   -->
                                                                   

<!-- ============================================================= -->
<!--                    DEFAULTS FOR ATTRIBUTE VALUES              -->
<!-- ============================================================= -->


<!--                    DEFAULT TYPE OF CROSS(X)-REFERENCE         -->
<!--                    Used to say to what the reference is pointing.
                        May be used for type-specific processing or
                        validation. Values are, for example:
                        Affiliation "aff", Figure "fig", and
                        Bibliographic ref (to a Citation <citation> or
                        to a Reference Item <ref>) "bibr"          -->
<!ENTITY % ref-types    "aff | app | author-notes | bibr | 
                         boxed-text | chem | contrib | corresp | 
                         disp-formula | fig | fn | kwd | list | 
                         plate | scheme | sec | statement | 
                         supplementary-material | 
                         table | table-fn | 
                         other"                                      >


<!-- ============================================================= -->
<!--                    DEFAULTS FOR ATTRIBUTE LISTS               -->
<!-- ============================================================= -->


<!--                    FOOTNOTE ATTRIBUTES                        -->
<!--                    Attribute list for Footnote element        -->
<!ENTITY %  fn-atts
             "id         ID                                #IMPLIED  
              symbol     CDATA                             #IMPLIED 
              fn-type    CDATA                             #IMPLIED  
              xml:lang   NMTOKEN                           #IMPLIED" > 


<!--                    INLINE SUPPLEMENTARY MATERIAL              -->
<!--                    Attribute list for inline supplementary 
                        material                                   -->
<!ENTITY %  inline-supplementary-material-atts
             "alternate-form-of
                        IDREF                             #IMPLIED
              content-type
                        CDATA                             #IMPLIED
              id        ID                                #IMPLIED
              %might-link-atts;                                    
              mimetype  CDATA                             #IMPLIED 
              mime-subtype
                        CDATA                             #IMPLIED"  >


<!--                    TARGET ATTRIBUTES                          -->
<!--                    Attribute list for <target> element        -->
<!ENTITY %  target-atts
             "id        ID                                #IMPLIED
              target-type
                        CDATA                             #REQUIRED" >


<!--                    X(CROSS) REFERENCE ATTRIBUTES              -->
<!--                    Attribute list for cross references        -->
<!ENTITY %  xref-atts
             "id         ID                               #IMPLIED
              ref-type   (%ref-types;)                    #IMPLIED 
              rid        IDREFS                           #IMPLIED"  >


<!-- ============================================================= -->
<!--                    INTERNAL LINKS                             -->
<!-- ============================================================= -->


<!--                    FOOTNOTE MODEL                             -->
<!--                    Content model for Footnote <fn>            -->
<!ENTITY % fn-model     "((%label.class;)?, (%just-para.class;)+ )"  > 


<!--                    FOOTNOTE                                   -->
<!--                    Additional information concerning material in
                        a particular location in the text. This
                        material is not considered to be part of the 
                        body of the text, but in addition to or a 
                        commentary on the body. Such material may be 
                        displayed at the bottom of a printed page, 
                        onscreen in a separate pop-up window, or in a
                        list at the end of an article.
                        Remarks: A reference (pointer) to a
                        Footnote <fn> is made with the X(Cross)
                        Reference element.
                        The language attribute may be used to note
                        a footnote that is not in the same language
                        as the original document, for example, a
                        Latin or Greek footnote for a document in 
                        English.                                   -->
<!ELEMENT  fn           %fn-model;                                   >
<!--         id         Unique identifier for the element. A cross-
                        reference will point to this ID.
             symbol     If the symbol that was used in the original
                        display to identify the specific footnote
                        is to be preserved, this is the attribute
                        where it may be stored. One might store the
                        symbol to disambiguate mistagged cases, for
                        example, in which the author has stated
                        "see footnote b" or "see footnote 14"  in
                        the text but the mention of the footnote has 
                        not been tagged as a cross references.
             fn-type    Type of footnote, for those footnotes that
                        point to a particular type of information 
                        and that type is known, this attribute is
                        intended as a way to preserve that
                        knowledge.  For example, some footnotes
                        point to or are used for the purpose of
                        recording:
                          abbr    Abbreviations
                          com     Communicated-by information
                          con     Contributed-by information
                          conflict
                                  Conflict of interest statements
                          equal   Contributed to the creation of
                                  the document equally
                          corresp For use when the corresponding
                                  author information is not 
                                  identified separately, but is 
                                  merely a footnote
                          current-aff
                                  Contributor's current affiliation
                          deceased
                                  Person has died since article was
                                  written
                          edited-by
                                  Contributor has the role of an
                                  editor
                          financial-disclosure
                                  Statement of funding or denial
                                  of funds received in support of
                                  the research on which this article
                                  is based
                          on-leave
                                  Contributor is on sabbatical or
                                  other leave of absence
                          participating-researchers
                                  Contributor was a researcher for
                                  this article
                          present-address
                                  Contributor's current address
                          presented-at
                                  Conference, colloquium, or other
                                  occasion at which this paper
                                  was presented
                          presented-by
                                  Contributor who presented this
                                  material
                          previously-at
                                  Contributor's previous location
                                  or affiliation
                          reprint Method or place to obtain reprints,
                                  typically the name and address of
                                  a person from whom reprints can be
                                  requested
                          study-group-members
                                  Contributor was a member of the
                                  study group for this research
                          supplementary-material
                                  Points to or describes
                                  supplementary material for this
                                  article
                          supported-by
                                  The research upon which this
                                  article is based was supported by
                          other    Not in the above list of
                                   footnote types
            xml:lang   The language in which the value of the
                        element is expressed.  Recommended best 
                        practice is to use values as defined in
                        RFC 1766, typically 2-letter language
                        codes such as "FR" (French), "EN" (English),
                        and "DE" (German). These values are NOT
                        case sensitive, so "EN" = "en". The values
                        may include hyphenated differentiations such 
                        as "EN-AU" (Australian English) and "EN-US"
                        (United States English).                   -->
<!ATTLIST  fn
             %fn-atts;                                               > 


<!--                    TARGET ELEMENTS                            -->
<!--                    The elements that can be included along with
                        data characters inside the content model of
                        a <target>  
                        Design Note: All inline mixes begin with an
                        OR bar, but since %link-elements; is an inline
                        mix, the OR bar is already there.          -->
<!ENTITY % target-elements
                        "%link-elements;"                            >


<!--                    TARGET OF AN INTERNAL LINK                 -->
<!--                    May be placed anywhere within textual 
                        material such as a paragraph to provide a
                        location (anchor) to which a cross reference
                        can point                                  -->
<!ELEMENT  target       (#PCDATA %target-elements;)*                 >
<!--         id         Unique identifier so the element may be
                        referenced
             target-type
                        Indicates the kind of <target> that has 
                        been created, i.e., describes the reason 
                        why some portion of text has been 
                        designated for cross-references purposes   -->
<!ATTLIST  target
             %target-atts;                                           >


<!--                    X(CROSS) REFERENCE ELEMENTS                -->
<!--                    The elements that can be included along with
                        data characters inside the content model of
                        an <xref>  
                        Design Note: All inline mixes begin with an
                        OR bar, but since %link-elements; is an inline
                        mix, the OR bar is already there.          -->
<!ENTITY % xref-elements
                        "%link-elements;"                            >

  
<!--                    X(CROSS) REFERENCE                         -->
<!--                    Used for any kind of internal article
                        referencing. The content of the reference 
                        (if present) will be displayed as the link.
                        This element may be used to point to any 
                        element that takes an "id" attribute.
                        The "ref-type" attribute may be used to name
                        the element or type of object to which the 
                        <xref> is pointing.                        -->
<!ELEMENT  xref         (#PCDATA %xref-elements;)*                   >
<!--         id         Unique identifier so the element may be
                        referenced (creating two-way link)
             ref-types  Used to say to what the reference is pointing.
                        May be used for type-specific processing or
                        validation.  
                        Values are:
                          aff       Affiliation
                          app       Appendix
                          author-note
                                    Author Note
                          bibr      Bibliographic ref (to 
                                    a Citation <citation>
                                    or to a Reference 
                                    Item <ref>) 
                          boxed-text
                                    Textbox or sidebar  
                          chem      Chemical Structure 
                                    Wrapper or Chemical
                                    Structure
                          contrib   Contributor
                          corresp   Corresponding Author
                          disp-formula        
                                    Display Formula 
                          fig       Figure or fig-group
                          kwd       Keyword
                          fn        Footnote
                          list      List 
                          plate     Plate
                          scheme    Scheme
                          sec       Section
                          statement Statement
                          supplementary-material  
                                    Supplementary Information
                          table     Table Group or Table Wrapper              
                          table-fn  Table foot Note
                                    A <fn> that is found within a
                                    <table-wrap> element and that
                                    should be displayed with the 
                                    table rather than, for example, 
                                    at the bottom of the page or 
                                    in a window that does not contain
                                    the table.
                          other     Not listed above               
             rid        Points to the identifier of a bibliographic
                        reference, boxed-text, figure, footnote, 
                        table, etc. (creating a link)              -->
<!ATTLIST  xref
             %xref-atts;                                             >


<!-- ============================================================= -->
<!--                    EXTERNAL LINKS                             -->
<!-- ============================================================= -->


<!--                    INLINE SUPPLEMENTARY MATERIAL ELEMENTS     -->
<!--                    Elements for use in the 
                        <inline-supplementary-material> element    -->
<!ENTITY % inline-supplementary-material-elements 
                        "| %access.class; | %address-link.class; | 
                         %emphasis.class; | %subsup.class;"          > 


<!--                    INLINE SUPPLEMENTARY MATERIAL              -->
<!--                    An in-text link to an external file that
                        provides supplementary information for
                        the document, for example, an audio clip   -->
<!ELEMENT  inline-supplementary-material
                        (#PCDATA 
                         %inline-supplementary-material-elements;)*  >
<!--         alternate-form-of
                        Where multiple formats of an item (e.g., 
                        graphic file, media object, chemical 
                        structure) are available, this attribute 
                        indicates that a format is a secondary 
                        one and provides a link to the primary 
                        format, so that only one format of an
                        item is displayed.
             content-type   
                        Identification of the subject, type of
                        content, or reason that this word or phrase
                        is considered semantically special, as a 
                        means of preserving the semantic intent of 
                        the original tagging.                      
             id         Unique identifier so the element may be
                        referenced                              
             mimetype   The mime type of the supplementary material
                        Authoring Note: This attribute might be
                        required when creating new articles.       
             mime-subtype   
                        The subtype of the supplementary material 
             xlink:href Provides an address or identifier of the
                        object to which the link points, for
                        example a URI or a filename                -->
<!ATTLIST  inline-supplementary-material
             %inline-supplementary-material-atts;                    >


<!-- ================== End Link Class Module ==================== -->
