Construct a href= using XSLT

Question

I want to create this:

<a href="domain.com?=USERNAME">Login</a>

where USERNAME = in XML so the HTML output is specific to the user currently logged in. Can anyone advise?

I know I can use:

<xsl:variable name="class" select="a:Subject"/>
<p class="{$class}">English</p>

To extract a value and use it as a CSS Class but what about using it for a link?

Answer 1

The same

<a href="domain.com?={$user}">OMG!</a>

Answer 2

Think I might have answered it myself:

<xsl:variable name="username" select="Username"/>
<a href="{$username}">Login</a>

Answer 3

What's wrong with using xsl:attribute?

<a><xsl:attribute name='href' select='Username' />Login</a>