<p><code>&lt;authors&gt;</code> nodes are in the <em>default namespace</em> <code>xmlns="http://arxiv.org/OAI/arXivRaw/"</code> which declared at the <code>&lt;arXivRaw&gt;</code> node level. </p>

<p>Many XPath platform (programming language API or other kind of XPath tools), provide a way to register mapping of namespace prefix to the corresponding namespace URI. In that case you need to register a prefix that points to <code>"http://arxiv.org/OAI/arXivRaw/"</code>, and use that prefix in your XPath. For example, assuming that the registered prefix named <code>d</code> :</p>

<pre><code>//d:authors
</code></pre>

<p>But in case there is no way, you can resort to use combination of Xpath's <code>local-name()</code> and <code>namespace-uri()</code> :</p>

<pre><code>//*[local-name()='authors' and namespace-uri()='http://arxiv.org/OAI/arXivRaw/']
</code></pre>

<p>or maybe just ignore the namespace for simplicity* :</p>

<pre><code>//*[local-name()='authors']
</code></pre>

<p>*) with risk of getting wrong nodes in case there are several nodes having same local name but different namespace</p>
Xpath returns always null for arXiv metadata
<p>I'm currently trying to parse some data from the arXiv. I was able to get the data in the xml format, but now I can't select certain elements. </p>

<p>For example, I want to get all authors from this xml file</p>

<p><a href="http://export.arxiv.org/oai2?verb=ListRecords&amp;set=physics:hep-th&amp;from=2015-03-30&amp;until=2015-03-31&amp;metadataPrefix=arXivRaw" rel="nofollow">http://export.arxiv.org/oai2?verb=ListRecords&amp;set=physics:hep-th&amp;from=2015-03-30&amp;until=2015-03-31&amp;metadataPrefix=arXivRaw</a></p>

<p>The xpath query</p>

<pre><code>//authors
</code></pre>

<p>or similar queries always return zero. Any ideas how to solve this problem would be great </p>