xslt - How to find ancestor-or-self that is a child of an element with particular attribute? -

i'm working generic xml structure, item (well relevant question anyway).

based on knowing item element i'm on , item element parent of node i'm looking for, need find item. have working xpath, it's resource intensive , i'm looking more elegant , cheaper.

the item key=a node parent of element i'm looking (though it's not child of document root)

xml:

<root>     <item key="a">         <item key="b">             <item key="c">                 <item key="d"/>             </item>         </item>         <item key="e">             <item key="f">                 <item key="g"/>             </item>         </item>     </item> </root> 

the actual xml deeper , far more branching.

so instance, if i'm on item key=g, e or f need return item key=e. if i'm on item key b,c or d need return item key=b.

i'm using xpath, working, going , down ancestor-descendant axis seems far longer trip need.

current()    /ancestor-or-self::item[@key='a']       /item[descendant-or-self::* = current()] 

is there simpler way of doing this, bearing in mind know 1) node i'm on , 2) key attribute of parent of node i'm looking for?

just detail's sake: xml sitecore generated, i'm not using current() function, i'm using sc_currentitem parameter set start node need begin processing at.

thanks in advance.

use:

ancestor-or-self::*[parent::item[@key='a']]