how can i extract and relate the value of the child xml value with the parent one with sed, awk or xmllint in bash unix?

Question

I have the following xml:

<Flusso cod_flusso="abc">
    <Identificativi>
        <piva_1>000000</piva_1>
        <piva_2>111111</piva_2>
    </Identificativi>
    <Dati>
        <cod>001100000111111</cod>
        <mese>01/2021</mese>
        <DatiTecn>
            <Tratt>G</Tratt>
            <coeff>1.0</coeff>
            <Racc>P</Racc>
            <esito>P</esito>
        </DatiTecn>
        <Letture>
            <matr>MIT00000000000000</matr>
            <data>01/01/2021</data>
            <tipo>E</tipo>
            <let>000003101</let>
        </Letture>
         <Letture>
            <matr>MIT00000000000000</matr>
            <data>02/01/2021</data>
            <tipo>E</tipo>
            <let>000003104</let>
        </Letture>
         <Letture>
            <matr>MIT00000000000000</matr>
            <data>03/01/2021</data>
            <tipo>E</tipo>
            <let>000003106</let>
        </Letture>
    </Dati>
</Flusso>

how can join cod value with data value using sed, awk or xmllint in bash unix and obtain the csv output:

001100000111111;01/01/2021 001100000111111;02/01/2021 001100000111111;03/01/2021

Answer 1

for the example this works, not sure what most general case is...

$ xmllint --xpath '//cod | //cod/following-sibling::*/data' file | 
  awk -F'[><]' 'NR==1{cod=$3; next} {printf "%s;%s ",cod,$3} END{print ""}' 

001100000111111;01/01/2021 001100000111111;02/01/2021 001100000111111;03/01/2021