This Tag Set allows citations to be tagged in two markedly different ways. Neither is superior to the other in supporting searching or making the citations into live links. Neither is inherently more semantically detailed than the other. One, the “mixed” style, mixes tags and text inside the citation content, and thus can preserve more closely the element order, punctuation, and spacing found in an original printed document or created editorially. The other, the “element” style, has only element content and does not contain any untagged text, which makes it possible to regularize the punctuation for references across a publication, publisher’s content management system, or archive’s content. It also requires that spacing and punctuation be created in formatting the content for display.
The “mixed” style is named because its content is what XML calls “mixed content”, a mixture of text and embedded elements. In this style, the citation is captured exactly as it was found in the print, complete with punctuation marks, line breaks, spaces, etc. It would be possible to tag a citation with just the <mixed-citation> element and text inside, though this is not best practice.
<mixed-citation>Petitti DB, Crooks VC, Buckwalter JG, Chiu V. Blood pressure levels before dementia. Arch Neurol. 2005 Jan; 62 (1): 112–116.</mixed-citation>
Although this Tag Set does not enforce it, best practice is to tag as many of the following elements as possible within a citation to a journal article, so that PubMed Central, CrossRef, or other matching services can make the journal citation into a live link:
In order to make a citation into a live link, as much of this author and date information as is available should be preserved, even if it is not possible to tag all the elements just named. The most important date tag is <year>, and it should always be tagged if possible, for example, <year>2003</year>. The <day>, <month>, and <season> elements are used more rarely; they are provided because some of the citation matching services can use the month and day information if it is available.
The simple citation we just examined would more properly be tagged with the name of the first author, the publication data (issue and volume), and the year of publication:
<mixed-citation> <string-name><surname>Petitti</surname> <given-names>DB</given-names> </string-name>, Crooks VC, Buckwalter JG, Chiu V. <article-title>Blood pressure levels before dementia</article-title>. <source>Arch Neurol</source>. <year>2005</year> Jan; <volume>62</volume>(<issue>1</issue>): <fpage>112</fpage>–116.</mixed-citation>
Best practice, however, is to tag as many of the author and publication details as possible for retrieval and linking purposes:
<mixed-citation publication-type="journal" publication-format="print"> <string-name><surname>Petitti</surname> <given-names>DB</given-names> </string-name>, <string-name><surname>Crooks</surname> <given-names>VC</given-names></string-name>, <string-name><surname>Buckwalter</surname> <given-names>JG</given-names> </string-name>, <string-name><surname>Chiu</surname> <given-names>V</given-names> </string-name>. <article-title>Blood pressure levels before dementia</article-title>. <source>Arch Neurol</source>. <year>2005</year> <month>Jan</month>; <volume>62</volume>(<issue>1</issue>): <fpage>112</fpage>–<lpage>116</lpage>.</mixed-citation>
The “element” style is named for its element content, as it is referred to in XML. Element content, unlike mixed content, does not include any text interspersed with the elements. In this model, any text that would not be separately tagged in a <mixed-citation> can be wrapped in a <comment> element, thus ensuring that all text is enclosed in tags. All punctuation marks, line breaks, spaces, etc. are removed from the tagged citation and must be replaced programmatically to view the citation in display or print. Also, there is the possibility that the display of existing content converted to element-style citations will not match the display of the same citations in their source documents. This is the style used to regularize the appearance of citations. Displaying this style of citation requires more complex output processing and means that all parts of the citation need to be tagged.
Although this Tag Set does not enforce it, best practice is to tag as many of the following elements as possible within a citation to a journal article or a book, so that PubMed Central, CrossRef, or other matching services can make the journal citation into a live link:
So the citation we just examined would be tagged as an element-style citation as follows:
<element-citation publication-type="journal" publication-format="print"> <name><surname>Petitti</surname><given-names>DB</given-names></name> <name><surname>Crooks</surname><given-names>VC</given-names></name> <name><surname>Buckwalter</surname><given-names>JG</given-names></name> <name><surname>Chiu</surname><given-names>V</given-names></name> <article-title>Blood pressure levels before dementia</article-title> <source>Arch Neurol</source><year>2005</year><month>Jan</month> <volume>62</volume><issue>1</issue><fpage>112</fpage><lpage>116</lpage> </element-citation>
Citations to journal articles should include elements that clearly identify the article. These identifying elements are used by citation matching services to make the articles into live links and by citation indexes in determining which articles are being cited. The most useful of the references elements for identifying journal articles are:
source | For journal article citations, this is the title of the journal in which the cited article was published. (Publishers and archives typically establish authority lists of journal titles. For example, in PubMed Central processing, the journal title source is usually the NLM title abbreviation of the journal name: <source>Physiol Rev</source>). For book citations, the source is the title of the book: <source>Moby Dick</source>.) |
article-title | Title of the journal article, typically in English. Usually this is the exact title as given in the print or display of the article: <article-title>The ethics of quackery and fraud in dentistry: a position paper</article-title>. Editorial added content, for example the word “[Retracted]”, should not be added to the title, but should follow the title as text or a <comment>. |
volume | The volume number of the journal in which the article was published, if applicable. |
issue | The issue number of the journal in which the article was published. The issue number element is typically just a simple counting number such as “4” or “35”, but some journals do simultaneous multiple issues, and in such cases both numbers should be placed inside the single <issue> element: <issue>4-5</issue>. |
fpage | Page number on which the article starts. (Although many citations also list the last page on which the article can be found (<lpage>), current citation matchers place more emphasis on the first page.) |
name | The name (typically the <surname>) of the first author or editor of the article. |
year | The year of publication. Multiple publication years (“2009-2010”) can be recorded in two ways: as successive <year> elements <year>2009</year>– <year>2010</year> or as a single combined year <year>2009–2010</year> |
month | The month of publication (if present). |
day | The day of publication if present. This is of lesser importance, but some citation matchers use it if it is available. |
The majority of the non-journal citations are for books, in whole or part. There are additional elements used in book citations that are rarely used for journals:
Here is a typical book, tagged in both element- and mixed-citation styles:
<element-citation publication-type="book" publication-format="print"> <collab>Joint Commission on Accreditation of Healthcare Organizations</collab> <source>Are you prepared? Hospital emergency management checklist</source> <publisher-name>Joint Commission Resources</publisher-name> <publisher-loc>Oak Brook (IL)</publisher-loc> <comment>Forthcoming 2006</comment> </element-citation> <mixed-citation publication-type="book" publication-format="print"> <collab>Joint Commission on Accreditation of Healthcare Organizations</collab>. <source>Are you prepared? Hospital emergency management checklist</source>. <publisher-loc>Oak Brook (IL)</publisher-loc>: <publisher-name>Joint Commission Resources</publisher-name>. Forthcoming 2006.</mixed-citation>
Here is a book in a non-print format, tagged in both element- and mixed-citation styles:
<element-citation publication-type="book" publication-format="mpic"> <source>Clinical tonometry</source> <comment>[motion picture]</comment> <collab collab-type="producer">Public Health Service Audiovisual Facility</collab> <publisher-loc>[Washington]</publisher-loc> <publisher-name>Department of Health, Education, and Welfare (US), Public Health Service</publisher-name><year>1965</year> <comment>1 reel: silent, black & white, 35 mm</comment> </element-citation> <mixed-citation publication-type="book" publication-format="mpic"> <source>Clinical tonometry</source> [motion picture]. <collab collab-type="producer">Public Health Service Audiovisual Facility</collab>, producer. <publisher-loc>[Washington]</publisher-loc>: <publisher-name>Department of Health, Education, and Welfare (US), Public Health Service</publisher-name>; <year>1965</year>. 1 reel: silent, black & white, 35mm.</mixed-citation>