<xref>
X (cross) Reference
Reference to an object within the document (for example, a table, a bibliographic
citation).
Remarks
This element may be used to reference anything that has an attribute of type
@id. This single element takes the place of
the many named types of references (such as figure references, table references, and
footnote references) that are common in many tag sets.
Best Practice: The @ref-type attribute (of the <xref> element) can be used to preserve information
concerning what type of element is being pointed to by the cross-reference.
Accessibility: Sometimes a <xref> needs to be pronounced in a way that is not reflected
in its content or its tagging. The @alt
attribute can be used to record the pronunciation for screen readers and other
accessibility devices. For example, the element cross-reference to a figure that follows
might be pronounced as “Figure 4”.
<p>... See <xref alt="figure 4">Fig IV.</xref></p>
Display/Formatting Note: The content of the reference
(if present) will be displayed as the link.
Attributes
Content Model
<!ELEMENT xref (#PCDATA %xref-elements;)* >
Expanded Content Model
(#PCDATA | email | ext-link | uri | inline-supplementary-material | related-article | related-object | hr | bold | fixed-case | italic | monospace | overline | overline-start | overline-end | roman | sans-serif | sc | serif | strike | underline | underline-start | underline-end | ruby | alternatives | inline-graphic | private-char | chem-struct | inline-formula | tex-math | mml:math | abbrev | index-term | index-term-range-end | milestone-end | milestone-start | named-content | styled-content | fn | target | xref | sub | sup | x | break)*
Description
Any combination of:
- Text, numbers, or special characters
- Linking Elements
- <inline-supplementary-material> Inline Supplementary Material
- Related Material Elements
- <hr> Horizontal Rule
- Emphasis Elements
- <bold> Bold
- <fixed-case> Fixed Case
- <italic> Italic
- <monospace> Monospace Text (Typewriter Text)
- <overline> Overline
- <overline-start> Overline Start
- <overline-end> Overline End
- <roman> Roman
- <sans-serif> Sans Serif
- <sc> Small Caps
- <serif> Serif
- <strike> Strike Through
- <underline> Underline
- <underline-start> Underline Start
- <underline-end> Underline End
- <ruby> Ruby Annotation Wrapper
- <alternatives> Alternatives For Processing
- Inline Display Elements
- <chem-struct> Chemical Structure (Display)
- <inline-formula> Formula, Inline
- Math Elements
- Other Inline Elements
- <fn> Footnote
- <target> Target of an Internal Link
- <xref> X (cross) Reference
- <sub> Subscript
- <sup> Superscript
- <x> X - Generated Text and Punctuation
- <break> Line Break
This element may be contained in:
<abbrev>, <addr-line>, <aff>, <alt-title>, <anonymous>, <article-title>, <attrib>, <award-id>, <bold>, <book-title>, <book-volume-id>, <book-volume-number>, <chapter-title>, <chem-struct>, <code>, <collab>, <comment>, <compound-kwd-part>, <conf-acronym>, <conf-loc>, <conf-name>, <conf-num>, <conf-sponsor>, <conf-theme>, <contrib>, <contrib-group>, <copyright-statement>, <corresp>, <def-head>, <degrees>, <disp-formula>, <edition>, <element-citation>, <email>, <etal>, <ext-link>, <fax>, <fixed-case>, <funding-source>, <funding-statement>, <given-names>, <gov>, <inline-formula>, <inline-supplementary-material>, <institution>, <issue>, <issue-part>, <issue-title>, <italic>, <kwd>, <label>, <license-p>, <meta-name>, <meta-value>, <mixed-citation>, <monospace>, <name-address-wrap>, <named-content>, <nav-pointer>, <on-behalf-of>, <overline>, <p>, <part-title>, <patent>, <phone>, <prefix>, <preformat>, <product>, <publisher-loc>, <publisher-name>, <rb>, <related-article>, <related-object>, <role>, <roman>, <sans-serif>, <sc>, <see>, <see-also>, <see-also-entry>, <see-entry>, <self-uri>, <series>, <serif>, <sig>, <sig-block>, <source>, <speaker>, <std-organization>, <strike>, <string-conf>, <string-date>, <string-name>, <styled-content>, <sub>, <subject>, <subtitle>, <suffix>, <sup>, <supplement>, <surname>, <target>, <td>, <term>, <term-head>, <th>, <title>, <trans-source>, <trans-subtitle>, <trans-title>, <underline>, <unstructured-kwd-group>, <uri>, <verse-line>, <version>, <volume>, <volume-id>, <volume-series>, <volume-title>, <xref>
Example 1
In the narrative text, cross-references to bibliographic references:
... <book-part> <book-part-meta>...</book-part-meta> <body> <p>... Although there is considerable descriptive literature on day hospital care,<xref ref-type="bibr" rid="B1">1</xref> concern has been expressed that evidence for effectiveness is equivocal and that day hospital care is expensive.<xref ref-type="bibr" rid="B2">2</xref> ...</p> ...</body> <back> ...<ref-list> <ref id="B1"><label>1</label> <element-citation publication-type="book"> <collab>Research Unit of the Royal College of Physicians and British Geriatric Society</collab> <source>Geriatric day hospitals: their role and guidelines for good practice</source> <publisher-loc>London</publisher-loc> <publisher-name>RCP</publisher-name> <year iso-8601-date="1994">1994</year> </element-citation> </ref> <ref id="B2">...</ref> ...</ref-list> ...</back> </book-part> ...
Example 2
In the narrative text, cross-references to figures:
...
<sec id="bid.36">
<title>Microbial Genomes</title>
<p>... A CON entry, containing instructions on how to put
the pieces back together, is also made. The CON entry
contains descriptor information, such as source organism
and references, as well as a join statement providing
explicit instructions on how to generate the complete
genome from the pieces. The Accession number assigned
to the CON record is also added as a secondary Accession
number on each of the pieces that make up the complete
genome (see <xref ref-type="fig" rid="bid.37">Figure 2</xref>).
<fig id="bid.37">
<label>2</label>
<caption>
<title>A GenBank CON entry for a complete bacterial
genome.</title>
<p>The information toward the <italic>bottom</italic> of the
record describes how to generate the complete genome
from the pieces.</p>
</caption>
<graphic xmlns:xlink="http://www.w3.org/1999/xlink"
xlink:href="ch1f2" mime-subtype="gif"/>
</fig>
</p>
...</sec>
...
...
<p>Allocation of tags to individual molecules is outlined in
<xref ref-type="fig" rid="F2" alt="figure two">Fig. 2</xref>.
First, the complete repertoire of tags in a plasmid library is
ligated to the entire population of cDNAs .... After separating
loaded microbeads from unloaded microbeads by FACS, as shown in
<xref ref-type="fig" rid="F4" alt="figure four">Fig. 4</xref>,
the hybridized DNA is ligated to the anti-tag, covalently attaching
one strand of the DNA to the microbead's surface. This permits easy
removal of the noncovalently attached strand.</p>
... Example 3
In metadata, cross-references linking authors to both affiliations and author notes:
... <book-part-meta>... <contrib-group> <contrib contrib-type="author"> <name-alternatives> <name name-style="western"><surname>Zhang</surname> <given-names>Y. P.</given-names></name> <string-name name-style="eastern" xml:lang="zh">张轶泼</string-name> </name-alternatives> <xref ref-type="aff" rid="a1">1</xref> <xref ref-type="author-notes" rid="n1">a)</xref> </contrib> <contrib contrib-type="author"> <name-alternatives> <name name-style="western"><surname>Isobe</surname> <given-names>M.</given-names></name> <string-name name-style="eastern" xml:lang="zh">磯部光孝</string-name> </name-alternatives> <xref ref-type="aff" rid="a2">2</xref> </contrib> <contrib contrib-type="author"> <name-alternatives> <name name-style="western"><surname>Liu</surname> <given-names>Yi</given-names></name> <string-name name-style="eastern" xml:lang="zh">刘仪</string-name> </name-alternatives> <xref ref-type="aff" rid="a1">1</xref> </contrib> </contrib-group> <aff id="a1">...</aff> <aff id="a2">...</aff> <author-notes id="n1">...</author-notes> </book-part-meta> ...