Used to record an identifier, such as a DOI, for elements other than the top-level element <article>
Such an identifier may be created by a publisher or archive, and there is no requirement that identifiers be unique.
Design Note: An element, rather than an attribute, was chosen as the means to capture DOIs and other identifiers so multiple identifiers could be retained.
<!ELEMENT object-id (#PCDATA) >
Text, numbers, or special characters
<boxed-text>, <chem-struct>, <chem-struct-wrap>, <element-citation>, <fig>, <graphic>, <media>, <mixed-citation>, <product>, <related-article>, <related-object>, <supplementary-material>, <table-wrap>
... <sec sec-type="results"> <title>Results</title> <p>We identified 703 abstracts, of which 687 were not relevant ... Details of randomisation procedures, treatment schedules, and numbers of patients followed up are given on the <italic>BMJ</italic> website.</p> <fig id="F1"> <caption> <title>Deaths among patients receiving day hospital care or alternative services.</title> <p>Odds ratios of death by end of follow up were calculated by fixed effects model. Heterogeneity between trials is presented as χ<sup>2</sup></p> </caption> <alt-text>Deaths in hospitals or with alternative services</alt-text> <graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="fors2662.f1" > <object-id>456472</object-id> </graphic> </fig> ... </sec> ...