question about implements-prefix

what purpose does the USER serve in the below code?  i know that it has to
be included, but am not sure of what it's use (if any) is.

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                xmlns:msxsl="urn:schemas-microsoft-com:xslt"
                xmlns:user="tbinder@xxxxxxxx"
                version="1.0">

  <msxsl:script language="VBScript" implements-prefix="user">
     function formatArg(idate)
       formatArg = ucase(idate)
     end function
  </msxsl:script>

  <xsl:template match="testcode">
    <xsl:value-of select="user:formatArg(date)"/>
  </xsl:template>

</xsl:stylesheet>

- Todd

Todd Binder
todd_binder@xxxxxxxxxxx

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