Bug 280682 – Support standalone MathML files in MML format

• Component: MathML
• Status: NEW

[Vadim Makeev]

Created attachment 472751 [details]
Standalone MathML file

There’s a .mml file extension [mentioned in the MathML 4.0 spec](https://w3c.github.io/mathml/#encoding-names) for standalone MathML files, just like .svg for SVG. And just like SVG, it’s an XML-based format that requires the `xmlns` attribute with a certain value to work and doesn’t need the `xmlns` when inlined in HTML.

```xml
<math xmlns="http://www.w3.org/1998/Math/MathML">
  <mrow>
    <msup>
      <mi>x</mi>
      <mn>2</mn>
    </msup>
    <mo>+</mo>
    <mi>y</mi>
  </mrow>
</math>
```

```xml
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 20 20">
 <rect width="20" height="20" fill="green" />
</svg>
```

Today, all browsers support rendering MathML inlined into HTML, but currently, only Firefox supports rendering MML files.

```html
<p>
  <math>
    <mrow>
      <msup>
        <mi>x</mi>
        <mn>2</mn>
      </msup>
      <mo>+</mo>
      <mi>y</mi>
    </mrow>
  </math>
</p>
```

```html
<p>
  <svg width="20" height="20" viewBox="0 0 20 20">
    <rect width="20" height="20" fill="green" />
  </svg>
</p>
```


The MML rendering in Firefox looks very similar to SVG: it takes the whole page, there’s XML in the view source and DOM in the DevTools, and it shows parsing error when the MML file is not well-formed. MML files also work when loaded in an iframe, but doesn’t work in `<img>`.

Both Safari and Chrome show MML as plain text. See the attached MML file example.

It’s not common to share MathML as standalone files. Still, it might be convenient/useful to store formulas in external files to reuse them in multiple content locations (inlined during build time, for example), just like SVG.

[Vadim Makeev]

Correction: Safari doesn’t show plain text for MML files, it downloads them.

Also, when renamed to .xml, both Safari and Chrome render MathML. Although they render `<math>` element centered, as it has `display="block"` attribute. Firefox renders `<math>` in the default inline mode.

Experiments with serving `application/mathml+xml` MIME type with a server response didn’t help much.

[Karl Dubost]

https://w3c.github.io/mathml/spec.html#encoding-names

> MathML (generic): The instance may contain presentation MathML markup, content MathML markup, or a mixture of the two.
> 
> File name extension: .mml
> Media Type: application/mathml+xml
> Windows Clipboard Flavor: MathML
> Universal Type Identifier: public.mathml


There is also 
https://w3c.github.io/mathml-docs/mathml-media-types/#media-types-mathml

[Radar WebKit Bug Importer]

<rdar://problem/137513021>