gistfile1.txt

xquery version "3.0";

declare function local:trim($arg as xs:string?) as xs:string {
    replace(replace($arg,'\s+$',''),'^\s+','')
} ;
    
    let $doc := doc('/foo/de/ayapedia/addendums/ernaehrung_9861fc6a-ba68-11e8-a8a1-001c4210b7a0/current-20180920-111838.bak/xml/index.xml')
    return 
        <item>
            <uri>{base-uri($doc)}</uri>
            <title>{local:trim($doc//meta[@name="Titel"]/value/text())}</title>    
            <description>{local:trim($doc//meta[@name="Beschreibung"]/value/text())}</description>    
            <language>{local:trim($doc//meta[@name="Sprache"]/value/text())}</language>    
            <status>{local:trim($doc//meta[@name="Status"]/value/text())}</status>    
            <area>{local:trim($doc//meta[@name="Bereich"]/value/text())}</area>    
            <path>{local:trim($doc//meta[@name="Pfad"]/value/text())}</path>    
            <date>{local:trim($doc//meta[@name="Stand"]/value/text())}</date>    
            <url>{local:trim($doc//meta[@name="URL"]/value/text())}</url>    
            <atc_code>{local:trim($doc//meta[@name="ATC"]/value/text())}</atc_code>    
            <guideline_id>{local:trim($doc//meta[@name="GuidelineID"]/value/text())}</guideline_id>    
            <plone_uuid>{local:trim($doc//meta[@name="PloneUUID"]/value/text())}</plone_uuid>    
            <old_authors_additional>{local:trim($doc//meta[@name="FruehereAutorenZusatzinformationen"]/value/text())}</old_authors_additional>    
            <authors_additional>{local:trim($doc//meta[@name="AutorenZusatzinformationen"]/value/text())}</authors_additional>    
            <documenttype>{local:trim($doc//meta[@name="DokumentTyp"]/value/text())}</documenttype>    
            {
                for $node in $doc//meta[@name="Fachgesellschaften"]/value
                return 
                    <societies json:array="true">{$node/text()}</societies>
            }    
            {
                for $node in $doc//meta[@name="Zulassungsland"]/value
                return 
                    <certification_countries json:array="true">{$node/text()}</certification_countries>
            }    
            {
                for $node in $doc//meta[@name="ICD10"]/value
                return 
                    <codes_icd10 json:array="true">{$node/text()}</codes_icd10>
            }    
            {
                for $node in $doc//meta[@name="LLThema"]/value
                return 
                    <guideline_topics json:array="true">{$node/text()}</guideline_topics>
            }    
            {
                for $node in $doc//meta[@name="Spezifikation"]/value
                return 
                    <specifications json:array="true">{$node/text()}</specifications>
            }    
            {
                for $node in $doc//meta[@name="Spezifikation2"]/value
                return 
                    <specifications2 json:array="true">{$node/text()}</specifications2>
            }    
            {
                for $node in $doc//meta[@name="Klassifizierung"]/value
                return 
                    <classifications json:array="true">{$node/text()}</classifications>
            }    
            {
                for $node in $doc//meta[@name="Autoren"]/value
                    return <authors json:array="true">{$node/text()}</authors>
            }
            {
                for $node in $doc//meta[@name="FruehereAutoren"]/value
                    return <old_authors json:array="true">{$node/text()}</old_authors>
            }
        </item>  

Output of XML under eXist-db and BaseX

<item>
  <uri>/foo/de/ayapedia/addendums/ernaehrung_9861fc6a-ba68-11e8-a8a1-001c4210b7a0/current-20180920-111838.bak/xml/index.xml</uri>
  <title>Ernährung</title>
  <description/>
  <language>de</language>
  <status>current</status>
  <area>ayapedia</area>
  <path/>
  <date>2018-09</date>
  <url/>
  <atc_code/>
  <guideline_id>bef53078-2d8d-42d1-af8c-b3d387dfa52e</guideline_id>
  <plone_uuid>464520ec154a42839b9f5d2635caccaf</plone_uuid>
  <old_authors_additional/>
  <authors_additional>für den Arbeitskreis Ernährung, Stoffwechsel und Bewegung der DGHO</authors_additional>
  <documenttype>ayapedia</documenttype>
  <societies xmlns:json="http://basex.org/modules/json" json:array="true">dgho</societies>
  <guideline_topics xmlns:json="http://basex.org/modules/json" json:array="true">183</guideline_topics>
  <authors xmlns:json="http://basex.org/modules/json" json:array="true">9211</authors>
  <authors xmlns:json="http://basex.org/modules/json" json:array="true">5577</authors>
  <authors xmlns:json="http://basex.org/modules/json" json:array="true">13728</authors>
  <authors xmlns:json="http://basex.org/modules/json" json:array="true">373215</authors>
</item>

JSON output eXist-DB:

{
   "status":"draft",
   "old_authors_additional":null,
   "guideline_id":"9861fc6a-ba68-11e8-a8a1-001c4210b7a0",
   "description":null,
   "language":"de",
   "area":"ayapedia",
   "url":null,
   "atc_code":null,
   "title":"Ern\u00e4hrung",
   "uri":"/db/onkopedia/de/ayapedia/addendums/ernaehrung_9861fc6a-ba68-11e8-a8a1-001c4210b7a0/draft/xml/index.xml",
   "authors_additional":"f\u00fcr den Arbeitskreis Ern\u00e4hrung, Stoffwechsel und Bewegung der DGHO",
   "authors":[
      "9211",
      "5577",
      "13728",
      "373215"
   ],
   "guideline_topics":[
      "183"
   ],
   "documenttype":"ayapedia",
   "date":"2018-09",
   "path":null,
   "plone_uuid":"0a85617d3c0c4b57b0c7b20d2b0c6d56",
   "societies":[
      "dgho"
   ]
}