Formula, Display

Mathematical equation, expression, or formula that is to be displayed as a block (callout) within the narrative flow.


A <disp-formula> need not be a “formula” in the strict mathematical sense, but can be used for any mathematical expression or equation.
This element may contain the actual characters that make up an equation or formula or a graphic that contains the formula. Thus, the mathematics can be expressed as ASCII characters; MathML, TeX, or LaTeX expressions; or as a graphic or series of graphics.
A display equation may numbered, using automatic numbering or by storing the number in a <label> element.

Related Elements

For a mathematical equation, expression, or formula which is to be displayed inline with the text, use the <inline-formula> element.


Content Model

<!ELEMENT  disp-formula %disp-formula-model;                         >

Expanded Content Model

(#PCDATA | alt-text | long-desc | email | ext-link | uri | break | bold | fixed-case | italic | monospace | overline | roman | sans-serif | sc | strike | underline | ruby | attrib | permissions | alternatives | inline-graphic | inline-media | chem-struct | inline-formula | label | mml:math | code | graphic | media | preformat | sub | sup)*


This element may be contained in:

Example 1

An equation tagged using TeX math:
<p>... This can be seen in the following summation:
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML">
<mml:mover accent='true'>


Example 2

Alternatives to an equation, including a graphic, XML-tagged MathML, and TeX tagging:
<disp-formula id="eq_002">
<graphic xlink:href="graphic/eq_002.png"/>
<mml:mstyle displaystyle="true" scriptlevel="0">
<mml:mi mathvariant="normal">&Delta;</mml:mi>
<mml:mi mathvariant="normal">&Delta;</mml:mi>
<mml:mi class="MJX-variant">&hbar;</mml:mi>