Expand compact xml representation to more verbose representation using xslt -

i'm trying learn xslt hobby, , 1 of use cases i'm interested in expansion of definitions of components complete forms. example should clarify mean. e.g. if input xml looks like:

<universe>     <galaxies>          <galaxy name="milky way">              <system name="solar system"/>          </galaxy>          <galaxy name="lactose free">              <system name="windmill system"/>          </galaxy>         <galaxy name="parallelish solar system">             <system name="the earth system"/>         </galaxy>     </galaxies>     <systems>         <system name="solar system">             <planet name="pluto"/>             <system name="the earth system"/>             <planet name="mercury"/>         </system>         <system name="windmill system">             <planet name="windy"/>         </system>         <system name="the earth system">             <planet name="earth"/>             <satellite name="moon"/>         </system>     </systems> </universe> 

my output xml have these system definitions expanded in galaxy definitions recursively (e.g. earth system in solar system) , in every single place definition occurs (e.g. earth system occurs in 2 different systems). systems section removed:

<universe>     <galaxies>         <galaxy name="milky way">             <system name="solar system">                 <planet name="pluto"/>                 <system name="the earth system">                     <planet name="earth"/>                     <satellite name="moon"/>                 </system>                 <planet name="mercury"/>             </system>         </galaxy>         <galaxy name="lactose free">             <system name="windmill system">                 <planet name="windy"/>             </system>         </galaxy>         <galaxy name="parallelish solar system">             <system name="the earth system">                 <planet name="earth"/>                 <satellite name="moon"/>             </system>         </galaxy>     </galaxies> </universe> 

i'm pretty new xslt, , of now, line of thought i've followed has been somehow define these component blocks variables , insert them appropriate in (second?) pass. however, i've googled around , read bit trying find examples, haven't been successful. i'm wondering if @ possible (i expect so), , concepts need use achieve this. example snippets helpful.

thanks!

xslt has useful keys mechanism resolving cross-references. demonstrate how work, have first modified xml example avoid circular references:

xml

<universe>     <galaxies>          <galaxy name="milky way">              <system-ref name="solar system"/>          </galaxy>          <galaxy name="lactose free">              <system-ref name="windmill system"/>          </galaxy>         <galaxy name="parallelish solar system">             <system-ref name="the earth system"/>         </galaxy>     </galaxies>     <systems>         <system name="solar system">             <planet name="pluto"/>             <system-ref name="the earth system"/>             <planet name="mercury"/>         </system>         <system name="windmill system">             <planet name="windy"/>         </system>         <system name="the earth system">             <planet name="earth"/>             <satellite name="moon"/>         </system>     </systems> </universe> 

xslt

<xsl:stylesheet version="1.0"  xmlns:xsl="http://www.w3.org/1999/xsl/transform"> <xsl:output method="xml" version="1.0" encoding="utf-8" indent="yes"/> <xsl:strip-space elements="*"/>  <xsl:key name="system-by-name" match="system" use="@name" />  <!-- identity transform --> <xsl:template match="@*|node()">     <xsl:copy>         <xsl:apply-templates select="@*|node()"/>     </xsl:copy> </xsl:template>  <xsl:template match="system-ref">     <xsl:apply-templates select="key('system-by-name', @name)"/> </xsl:template>  <xsl:template match="systems"/>  </xsl:stylesheet> 

result

<?xml version="1.0" encoding="utf-8"?> <universe>    <galaxies>       <galaxy name="milky way">          <system name="solar system">             <planet name="pluto"/>             <system name="the earth system">                <planet name="earth"/>                <satellite name="moon"/>             </system>             <planet name="mercury"/>          </system>       </galaxy>       <galaxy name="lactose free">          <system name="windmill system">             <planet name="windy"/>          </system>       </galaxy>       <galaxy name="parallelish solar system">          <system name="the earth system">             <planet name="earth"/>             <satellite name="moon"/>          </system>       </galaxy>    </galaxies> </universe>