Hi all, I thought this was easy, but I overestimated my competence… I want to filter xml elements via their attributes and retrieve and typeset parts belonging together. Here is a small test file that explains what I’m trying: \startbuffer[test] <document> <topics> <topic id="test1"> <title>This is the first test</title> <date>22/11/16</date> </topic> <topic id="test2"> <title>This is the second test</title> <date>22/11/17</date> </topic> </topics> <chapters> <chapter id="test1"> <content> This will be the content of the <emph>first</emph> chapter. </content> </chapter> <chapter id="test2"> <content> This will be the content of the <emph>second</emph> chapter. </content> </chapter> </chapters> </document> \stopbuffer \startxmlsetups xml:testsetups \xmlsetsetup{#1}{*}{-} \xmlsetsetup{#1}{document|chapters|chapter|content|emph}{xml:*} \stopxmlsetups \xmlregistersetup{xml:testsetups} \startxmlsetups xml:document \xmlflush{#1} \stopxmlsetups \startxmlsetups xml:chapters \xmlflush{#1} \stopxmlsetups \startxmlsetups xml:chapter \xmlfunction {#1} {chapter} \xmlflush {#1} \stopxmlsetups \startxmlsetups xml:chapter:content \xmltext {#1} {content} \stopxmlsetups \startxmlsetups xml:emph {\em \xmlflush {#1}} \stopxmlsetups \startluacode function xml.functions.chapter (t) local ch_id = t.at.id local metadata = xml.filter (root, '../../topics/topic[@id=="%s"]', ch_id) print (inspect(metadata)) lxml.command(t, ".", "xml:chapter:content") context.par () context (ch_id) context.par () end \stopluacode \starttext \xmlprocessbuffer{main}{test}{} \stoptext The line with xml.filter does not work as I expected. How can I walk the tree, find the “topic” element with the same “id” attribute as the chapter I’m currently in, and then typeset the different children of the topic element? Thanks a lot and all best Thomas