mml2tex

mml2tex is an XProc/XSLT-library to convert MathML to LaTeX.

It should currently support MathML 2 and 3 presentation markup. Content markup and some MathML 1 elements are not supported.

You may either invoke mml2tex standalone or include it as library in your XSLT or XProc project. The LaTeX code is wrapped in processing instructions named mml2tex.

This library is also used in docx2tex that converts Word docx files with OOMML (= new equation editor) formulas to LaTeX.

Consider this XML input file …

<?xml version="1.0" encoding="UTF-8"?>
<article xmlns="http://docbook.org/ns/docbook" version="5.0">
  <title>Area enclosed by a circle</title>
  <equation>
    <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML">
      <mml:mi>A</mml:mi>
      <mml:mo>=</mml:mo>
      <mml:mi>π</mml:mi>
      <mml:msup>
        <mml:mrow>
          <mml:mi>r</mml:mi>
        </mml:mrow>
        <mml:mrow>
          <mml:mn>2</mml:mn>
        </mml:mrow>
      </mml:msup>
    </mml:math>
  </equation>
</article>

… you should get this output:

<?xml version="1.0" encoding="UTF-8"?><article xmlns="http://docbook.org/ns/docbook" version="5.0">
  <title>Area enclosed by a circle</title>
  <equation>
    <?mml2tex A=\pi r^{2}?>
  </equation>
</article>

Invoke standalone

mml2tex is a library rather than a standalone stylesheet. If you intend to run mml2tex standalone, you need to include the dependencies, add a proper XML catalog and invoke Saxon with XML resolver support.

mkdir myProjectDir
cd myProjectDir
git clone [email protected]:transpect/mml2tex.git
git clone [email protected]:transpect/xslt-util.git
mkdir xmlcatalog
touch xmlcatalog/catalog.xml

Then edit xmlcatalog/catalog.xml with your text editor of choice:

<?xml version="1.0" encoding="UTF-8"?>
<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog">
  <nextCatalog catalog="../xslt-util/xmlcatalog/catalog.xml"/>
</catalog>

Download Apache XML Commons Resolver and invoke Saxon:

java -cp "C:/home/myUsername/xmltools/saxon/saxon9he.jar;C:/home/myUsername/xmltools/xml-commons-resolver/resolver.jar" \
-Dxml.catalog.files=C:/home/myUsername/myProjectDir/xmlcatalog/catalog.xml \
net.sf.saxon.Transform \
-catalog:xmlcatalog/catalog.xml \
-xsl:mml2tex/xsl/invoke-mml2tex.xsl \
-s:mml2tex/example/example.xml

Include as XSLT library

You have to import mml2tex.xsl in your XSLT stylesheet and create a template that matches on the MathML equations. The MathML markup must be processed within the mathml2tex mode. You can take xsl/mml2tex.xsl as example:

<?xml version="1.0" encoding="UTF-8" ?>
<xsl:stylesheet version="2.0" 
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform" 
  xmlns:fn="http://www.w3.org/2005/xpath-functions"
  xmlns:xs="http://www.w3.org/2001/XMLSchema" 
  xmlns:saxon="http://saxon.sf.net/" 
  xmlns:tr="http://transpect.io"
  xmlns:mml="http://www.w3.org/1998/Math/MathML"
  exclude-result-prefixes="saxon tr fn mml xs">
  
  <xsl:import href="mml2tex.xsl"/>
  
  <xsl:output method="xml" encoding="UTF-8"/>
  
  <xsl:preserve-space elements="mml:mn mml:mi mml:mtext mml:mo mml:ms"/>
  
  <xsl:param name="debug" select="'no'"/>
  <xsl:param name="debug-dir-uri" select="'debug'"/>
  
  <xsl:template match="mml:math">
    <xsl:processing-instruction name="mml2tex">
      <xsl:apply-templates select="." mode="mathml2tex"/>
    </xsl:processing-instruction>
  </xsl:template>
  
  <xsl:template match="*|@*|processing-instruction()">
    <xsl:copy>
      <xsl:apply-templates select="@*|node()"/>
    </xsl:copy>
  </xsl:template>
  
  <xsl:template match="/">
    <xsl:copy>
      <xsl:apply-templates/>
    </xsl:copy>
  </xsl:template>
  
</xsl:stylesheet>

Note: You may omit the xsl:processing-instruction. Then the LaTeX code will be issued as plain text. This method is not recommended, because subsequent text replacements may break your LaTeX code. It's better to leave the LaTeX code within the processing instruction and resolve it as last step.

Include as XProc library

Get dependencies

Running mml2tex requires an XProc processor, the libary store-debug.xpl and of course mml2tex. To facilitate the invocation of the XProc pipeline, we recommend to use our patched calabash-frontend. You can checkout the repositories with Git or SVN.

Git

$ git clone https://github.com/transpect/calabash-frontend calabash --recursive
$ git clone https://github.com/transpect/cascade
$ git clone https://github.com/transpect/mml-normalize
$ git clone https://github.com/transpect/mml2tex
$ git clone https://github.com/transpect/xproc-util
$ git clone https://github.com/transpect/xslt-util

SVN

$ svn co https://github.com/transpect/calabash-frontend/trunk calabash
$ svn co https://github.com/transpect/cascade/trunk cascade
$ svn co https://github.com/transpect/mml-normalize/trunk mml-normalize
$ svn co https://github.com/transpect/mml2tex/trunk mml2tex
$ svn co https://github.com/transpect/xproc-util/trunk xproc-util
$ svn co https://github.com/transpect/xslt-util-util/trunk xslt-util

Create an XML catalog

As a convention, our calabash frontend looks after an XML catalog file under xmlcatalog/catalog.xml. Therefore you have to create the directory and the file.

$ mkdir xmlcatalog
$ touch xmlcatalog/catalog.xml

The catalog is necessary to resolve canonical URIs in import statements, such as http://transpect.io/mml2tex/xpl/mml2tex.xpl. Therefore, you have to edit the file catalog.xml and add appropriate rewriteURI statements for your dependencies.

<?xml version="1.0" encoding="UTF-8"?>
<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog">

  <nextCatalog catalog="../cascade/xmlcatalog/catalog.xml"/>
  <nextCatalog catalog="../mml-normalize/xmlcatalog/catalog.xml"/>
  <nextCatalog catalog="../mml2tex/xmlcatalog/catalog.xml"/>
  <nextCatalog catalog="../xproc-util/xmlcatalog/catalog.xml"/>
  <nextCatalog catalog="../xslt-util/xmlcatalog/catalog.xml"/>
  
</catalog>

Include mml2tex in your XProc pipeline

The step mml2tex:convert facilitates the use of the mml2tex library in your XProc pipeline. As prerequisites, you must add the namespace http://transpect.io/mml2tex and a p:import statement. A sample test.xpl may look like this:

<?xml version="1.0" encoding="UTF-8"?>
<p:declare-step xmlns:p="http://www.w3.org/ns/xproc"
  xmlns:c="http://www.w3.org/ns/xproc-step" 
  xmlns:mml2tex="http://transpect.io/mml2tex"
  version="1.0">
  
  <p:input port="source">
    <p:inline>
      <article xmlns="http://docbook.org/ns/docbook" version="5.0">
        <title>Area enclosed by a circle</title>
        <equation>
          <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>A</mml:mi><mml:mo>=</mml:mo><mml:mi>π</mml:mi><mml:msup><mml:mrow><mml:mi>r</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:math>     
        </equation>
      </article>
    </p:inline>
  </p:input>
  
  <p:output port="result"/>
  
  <p:option name="debug"         select="'no'"/>   <!-- store debug files: yes | no -->
  <p:option name="debug-dir-uri" select="'debug'"/><!-- store debug files to this URI -->
  
  <p:import href="http://transpect.io/mml2tex/xpl/mml2tex.xpl"/>
  <p:import href="http://transpect.io/xproc-util/store-debug/xpl/store-debug.xpl"/>
  
  <mml2tex:convert>
    <p:with-option name="debug" select="$debug"/>
    <p:with-option name="debug-dir-uri" select="$debug-dir-uri"/>
  </mml2tex:convert>
  
</p:declare-step>

Run the pipeline

We provide frontend scripts for XML Calabash which look after the XML catalogs, make some paths suitable for XProc and add some Java libraries to the class path. There is a Bash script for Unix-like operating systems as well as an Batch file for Windows. You can find them in the calabash directory.

$ ./calabash/calabash.sh test.xpl

Alternative XSLT-only invocation for KaTeX-compatible output

$ saxon/saxon.sh -xsl:mml2tex/xsl/katexify.xsl -s:mml2tex/example/katexify-example.xml -im:mathml2tex

Assumptions: A Saxon front-end script is present in the current (project) directory, for example by

$ svn co https://subversion.le-tex.de/common/saxon-pe98/ saxon

And the additional transpect libraries xslt-util, xproc-util, cascade, and normalize-mml are present (all from https://github.com/transpect/[library]) in the project directory, see above.

And there is an xmlcatalog/catalog.xml that imports the library catalogs using nextCatalog instructions.

The Saxon front-end script will look for and use this catalog by default.

Input:

<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML">
  <mml:mi>Γ</mml:mi>
  <mml:mo>=</mml:mo>
  <mml:mi>π</mml:mi>
  <mml:msup>
    <mml:mrow>
      <mml:mi>r</mml:mi>
    </mml:mrow>
    <mml:mrow>
      <mml:mn>2</mml:mn>
    </mml:mrow>
  </mml:msup>
</mml:math>

Output:

\Gamma = \pi r ^{2}