<section id="sec-epub-rs-i18n">

<h2>Internationalization</h2>

<p>

A Reading System MUST process, for all <a href="https://www.w3.org/TR/epub-33/#dfn-publication-resource">Publication Resources</a>, the attributes that set the primary language for the documents' contents, when applicable. This includes:

</p>

<ul>

<li>

the <code>xml:lang</code> attribute for all XML documents like the

<a href="https://www.w3.org/TR/epub-33/#attrdef-xml-lang">Package Document</a>

or the <a href="https://www.w3.org/TR/epub-33/#sec-overlay-docs">Media Overlay

Document</a> [[!EPUB-33]].

</li>

<li>

the <code>xml:lang</code> and <code>lang</code> attributes for

<a href="https://html.spec.whatwg.org/multipage/dom.html#the-lang-and-xml:lang-attributes">XHTML</a> [[!HTML]]

or <a href="https://www.w3.org/TR/SVG/struct.html#LangSpaceAttrs">SVG</a> [[!SVG]].

</li>

</ul>

<p>

Similarly, a Reading System MUST process, for all <a href="https://www.w3.org/TR/epub-33/#dfn-publication-resource">Publication Resources</a>, the attributes that set the base direction

for the documents' contents, when applicable. This includes:

</p>

<ul>

<li>

the <code>dir</code> attribute for the

<a href="https://www.w3.org/TR/epub-33/#attrdef-dir">Package Document</a> [[!EPUB-33]].

(See also <a href="#sec-pkg-doc-base-dir"></a> for further details.)

</li>

<li>

the <code>dir</code> attribute for <a href="https://html.spec.whatwg.org/multipage/dom.html#the-dir-attribute">XHTML</a> [[!HTML]].

</li>

<li>

the <code>direction</code> attribute for <a href="https://www.w3.org/TR/SVG2/text.html#DirectionProperty">SVG</a> [[!SVG]].

</li>

</ul>

<p>

In the absence of this information in a <a>Publication Resource</a>, Reading Systems MUST NOT assume either the language or the base direction of that resource from information expressed in the Package Document (i.e., in <code>xml:lang</code> and <code>dir</code> attributes, in <code>hreflang</code> attributes on link elements, or from <code>dc:language</code> elements). The handling of documents without explicit language or direction is defined in their respective specifications.

</p>

</section>

<p>

The language(s) of the <a>EPUB Publication</a> specified in <code>language</code> elements

are informational. Some uses of this information include:

</p>

<ul>

<li>exposing it to the user through the Reading System user interface</li>

<li>using it to enhance functionality in a bookshelf (e.g., sorting by language)</li>

<li>using it to optimize the reading interface (e.g., to preload text-to-speech languages)</li>

</ul>

<p>See <a href="#sec-epub-rs-i18n"></a> for more details on how to determine the language of a <a>Publication Resource</a>.</p>