<semantics> - MathML 编辑

In MathML there are two ways to mark up mathematics: Presentation MathML is used to control the layout of equations, whereas Content MathML is designed to encode the semantic mathematical meaning and to make expressions understandable to computer algebra systems. The MathML elements <semantics>, <annotation> and <annotation-xml> are used to combine presentation and content markup and to provide both, layout information and semantic meaning of mathematical expressions.

The <semantics> element acts as a container element associating annotations and must have child elements (it will raise an invalid markup error otherwise). The <annotation> element is the container element containing semantic information in a non-XML format, whereas the <annotation-xml> element contains content in an XML format, e.g. Content MathML or OpenMath.

The rules of determining the visible child in a <semantics> element are the following:

• If no rule other rule applies: By default only the first child is rendered, which is supposed to be presentation markup.
• If the first child is a presentation MathML element other than <annotation> or <annotation-xml>, render the first child.
• If no Presentation MathML is found, render the first <annotation> or <annotation-xml> child element of <semantics>.
  Beware that <annotation-xml> elements are only recognized, if the encoding attribute is set to one of the following:
  • "application/mathml-presentation+xml"
  • "MathML-Presentation"
  • "SVG1.1"
  • "text/html"
  • "image/svg+xml"
  • "application/xml".
  Note that "application/mathml+xml" is not mentioned here as it does not distinguish between Content or Presentation MathML.

Attributes

The following attributes can be set on <annotation> and <annotation-xml>:

definitionURL

The location of the annotation key symbol.

displaystyle

A Boolean value specifying whether more vertical space is used for displayed equations or, if set to false, a more compact layout is used to display formulas. The main effect is that larger versions of operators are displayed, when displaystyle is set to true. See also largeop and movablelimits on <mo>.

encoding

The encoding of the semantic information in the annotation (e.g. "MathML-Content", "MathML-Presentation", "application/openmath+xml", "image/png")

cd

The content dictionary that contains the annotation key symbol.

name

The name of the annotation key symbol.

src

The location of an external source for semantic information.

Example

<math>
  <semantics>

    <!-- Presentation MathML -->
    <mrow>
      <msup>
        <mi>x</mi>
        <mn>2</mn>
      </msup>
      <mo>+</mo>
      <mi>y</mi>
    </mrow>

    <!-- Content MathML -->
    <annotation-xml encoding="MathML-Content">
      <apply>
        <plus/>
        <apply>
          <power/>
          <ci>x</ci>
          <cn type="integer">2</cn>
        </apply>
        <ci>y</ci>
      </apply>
    </annotation-xml>

    <!-- annotate an image -->
    <annotation encoding="image/png" src="some/path/formula.png"/>

    <!-- annotate TeX -->
    <annotation encoding="application/x-tex">
      x^{2} + y
    </annotation>

  </semantics>
</math>

Specifications

Browser compatibility

BCD tables only load in the browser

Gecko-specific notes

• The algorithm of determining the visible child in <semantics> has been corrected in (Firefox 23 / Thunderbird 23 / SeaMonkey 2.20) to match the MathML specification. In prior versions the first child element has been rendered.
• In Gecko <annotation> and <annotation-xml> elements are ignored if the src attribute is set.