What is the "fastest" way to convert a sequence of text nodes into one
single text node in XPath2.0?

I could do it outside of an XPath expression by applying xsl:value-of

    <xsl:param name="text" as="xs:string">
       <xsl:value-of select="@name"/>
    </xsl:param>

but I would like to have it more compact, something like:

    <xsl:param name="text" select="mysterious-function(@name)"
as="xs:string"/>

(mysterious-function should be a standard function, not one by me that
encapsulates xsl:value-of :-), but I don't know if such a construct exists)

<xsl:value-of>
 <xsl:text>foo</xsl:text>
 <xsl:text>bar</xsl:text>
</xsl:value-of>

In your example though, how would an attribute return a sequence of
multiple text nodes?