Attribute Value Templates - xspec/xspec GitHub Wiki
Attribute values in embedded XML work as AVT.
Depending on your purpose, you can use an expression:
<x:param name="base-uri" select="'http://www.example.com/'" />
<x:scenario label="when using expression in attribute">
<x:call function="my:func">
<!-- Will be resolved as <option file="http://www.example.com/dir/file.txt" /> -->
<x:param>
<option file="{$base-uri}dir/file.txt" />
</x:param>
</x:call>
...
</x:scenario>or you may need to escape (i.e. double) the curly braces:
<x:scenario label="when escaping curly braces in attribute">
<!-- Will be resolved as <element path="/Q{http://www.example.com}foo" /> -->
<x:context>
<element path="/Q{{http://www.example.com}}foo" />
</x:context>
...
</x:scenario>