> I only need this part of stylesheet to substitute a few 
> element names and copy the rest unchanged.
> What should I do then to make the substitution code work on 
> the element that are unmatche by the mapping file?

Something like this

<xsl:element name="{($maps[@old = local-name(current())]/@new, @old)[1]}">

The idiom (A,B)[1] means "A if it exists, otherwise B".

Michael Kay
http://www.saxonica.com/